- Email: [email protected]
Psychometric evaluation of the Generalized Anxiety Disorder Screener GAD-7, based on a large German general population sample
Author’s Accepted Manuscript Psychometric evaluation of the Generalized Anxiety Disorder Screener GAD-7, based on a large German general population sample Andreas Hinz, Annette M. Klein, Elmar Brähler, Heide Glaesmer, Tobias Luck, Steffi G. RiedelHeller, Kerstin Wirkner, Anja Hilbert www.elsevier.com/locate/jad
PII: DOI: Reference:
S0165-0327(16)31369-6 http://dx.doi.org/10.1016/j.jad.2016.12.012 JAD8673
To appear in: Journal of Affective Disorders Received date: 10 August 2016 Revised date: 11 November 2016 Accepted date: 16 December 2016 Cite this article as: Andreas Hinz, Annette M. Klein, Elmar Brähler, Heide Glaesmer, Tobias Luck, Steffi G. Riedel-Heller, Kerstin Wirkner and Anja Hilbert, Psychometric evaluation of the Generalized Anxiety Disorder Screener GAD-7, based on a large German general population sample, Journal of Affective Disorders, http://dx.doi.org/10.1016/j.jad.2016.12.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1 Psychometric evaluation of the Generalized Anxiety Disorder Screener GAD-7, based on a large German general population sample Andreas Hinz a*, Annette M. Klein b, Elmar Brähler a,c, Heide Glaesmer a, Tobias Luck d,e, Steffi G. Riedel-Heller d, Kerstin Wirkner e, Anja Hilbert f a
Department of Medical Psychology and Medical Sociology, University of Leipzig, Leipzig,
Germany b
Department of Child and Adolescent Psychiatry, Psychotherapy, and Psychosomatics ,
University of Leipzig, Leipzig, Germany c
Clinic for Psychosomatic Medicine and Psychotherapy, University Medical Center of the
Johannes Gutenberg University, 55131 Mainz, Germany. d
Institute of Social Medicine, Occupational Health, and Public Health, University of Leipzig,
Leipzig, Germany e
LIFE – Leipzig Research Center for Civilization Diseases, University of Leipzig, Leipzig,
Germany f
Leipzig University Medical Center, Integrated Research and Treatment Center Adiposity
Diseases, University of Leipzig, Leipzig Germany *
Corresponding author: Andreas Hinz, Department of Medical Psychology and Medical
Sociology, University of Leipzig, Philipp-Rosenthal-Str. 55, 04103 Leipzig, Germany. Phone: +49 341 9718820; Fax: +49 341 9718809. [email protected] Abstract Background: The Generalized Anxiety Disorder Scales GAD-7 and GAD-2 are instruments for the assessment of anxiety. The aims of this study are to test psychometric properties of these questionnaires, to provide normative values, and to investigate associations with sociodemographic factors, quality of life, psychological variables, and behavioral factors. Methods: A German community sample (n = 9721) with an age range of 18-80 years was surveyed using the GAD-7 and several other questionnaires. Results: Confirmatory factor analyses confirmed the unidimensionality and measurement invariance of the GAD-7 across age and gender. Females were more anxious than males (mean scores: M = 4.07 vs. M = 3.01; effect size: d = 0.33). There was no linear age trend. A total of 5.9 % fulfilled the cut-off criterion of 10 and above. Anxiety was correlated with
2 low quality of life, fatigue, low habitual optimism, physical complaints, sleep problems, low life satisfaction, low social support, low education, unemployment, and low income. Cigarette smoking and alcohol consumption were also associated with heightened anxiety, especially in women. When comparing the GAD-7 (7 items) with the ultra-short GAD-2 (2 items), the GAD-7 instrument was superior to the GAD-2 regarding several psychometric criteria.. Limitations: The response rate (33%) was low. Because of the cross-sectional character of the study, causal conclusions cannot be drawn. A further limitation is the lack of a gold standard for diagnosing anxiety. Conclusions: The GAD-7 can be recommended for use in clinical research and routine.
Keywords: Anxiety; General population; Epidemiology; Normative values
1. Introduction
Generalized anxiety disorder (GAD) is one of the most common mental disorders (Remes et al., 2016; Somers et al., 2006). Its lifetime prevalence is estimated to be 6.2 % (Somers et al., 2006), and it often remains undetected by physicians (Parmentier et al., 2013). Therefore, several screening instruments have been developed for effectively identifying patients with GAD (Kroenke et al., 2007; McHugh et al., 2011). One of these instruments is the Generalized Anxiety Disorder Scale GAD-7, developed by Spitzer and colleagues (Spitzer et al., 2006). This questionnaire indicates the presence of symptoms of GAD referred to in the DSM-IV. While in the DSM-5 the anxiety disorder spectrum was rearranged into separate groupings for the ‘classical’ anxiety disorders, trauma- and stressor-related disorders, obsessive-compulsive and related disorders, and dissociative disorders, the criteria for GAD did not change significantly as compared with DSM-IV. The GADS-7 has been translated into several languages and validated in multiple studies, e. g., (Beard and Bjorgvinsson, 2014; Seo and Park, 2015; Plummer et al., 2016). Normative values of a questionnaire are essential for assessing individuals’ and groups of patients’ level of burden. While it is common for well-established questionnaires to be tested in multiple normative studies, the research literature on normative values of the GAD-7 is very limited. There is only one large normative examination of adult people from the general population (Löwe et al., 2008). This study confirmed age and gender factorial
3 invariance of the GAD-7 factor structure. Detailed analyses of this data set have been published separately for men (Beutel et al., 2010) and women (Beutel et al., 2009). Two new studies with general population samples from Germany (Wild et al., 2014) and Canada (Vasiliadis et al., 2015) were recently performed with elderly people. Several studies examining patients with anxiety disorders used controls without such disorders (Ruiz et al., 2011; Konkan et al., 2013), but their sample sizes were low. There is considerable heterogeneity in the GAD-7 mean scores of the examinations of people from the general population, with values ranging from 2.0 (Wild et al., 2014) to 8.0 (Donker et al., 2011), which underlines the necessity of providing sound normative values. Females are more anxious than males, but these gender differences were also not identical across studies. Those difference scores ranged from 0.54 (Löwe et al., 2008) to 1.31 (Vasiliadis et al., 2015). There were also small and nonlinear age differences in these examinations. Validation studies identified different optimal cut-off scores for detecting GAD, ranging from 5 to 12 (Schalet et al., 2014; Vasiliadis et al., 2015; Kujanpaa et al., 2014; García-Campayo et al., 2010; Donker et al., 2011; Plummer et al., 2016). According to the original cut-off, 10 and above (10+), 6% of the sample from the normative study (Löwe et al., 2008) showed heightened levels of anxiety. Anxiety as measured with the GAD-7 proved to be strongly associated with depression with r = 0.71 (García-Campayo et al., 2010), r = 0.70 (Wild et al., 2014), and r = 0.64 (Löwe et al., 2008). In addition, GAD-7 anxiety was correlated with physical complaints (r = 0.51) (Gierk et al., 2015), headache (r = 0.40) (Seo & Park, 2015), disability (r = 0.70) (García-Campayo et al., 2010), lack of self esteem (r = -0.43) (Löwe et al., 2008), and lack of life satisfaction (r = -0.34) (Löwe et al., 2008). These studies differed with regard to the samples (general population or patients), age and gender distribution, sample size, and country. Therefore, the correlations cannot be directly compared with one another. In our study we used several questionnaires covering quality of life, life satisfaction, fatigue, optimism, physical complaints, sleep problems, and social support to specify the magnitude of the association with anxiety in a comparable way. In addition, we intended to investigate the associations with socioeconomic factors (education, occupational status, and income) as well as behavioral factors (smoking and alcohol intake). The GAD-2 is an ultra-short GAD questionnaire. It consists of the two psychometrically best items from the GAD-7. This GAD-2 is also part of the Patient Health Questionnaire-4 (PHQ-4) (Löwe et al., 2010), which additionally contains two depression items from the PHQ-9 (Kroenke et al., 2001). The cut-off 3+ was found to be optimal for the GAD-2 (Plummer et al., 2016). It is likely that the psychometric properties of a 2-item-
4 instrument will not be as good as those of an instrument with 7 items. However, the difference in psychometric accuracy between the GAD-7 and the GAD-2 has not been systematically tested yet. The aims of this study were - to analyze age and gender differences in anxiety, measured with the GAD-7 and the GAD-2, - to test psychometric properties of the GAD-7 and the GAD-2, including calculations of measurement equivalence and convergent validity, and - to test the associations between anxiety sociodemographic factors, quality of life, psychological variables, and behavioral factors, based on a large sample of the general population.
2.1.
Sample
Data were derived from the LIFE-Adult-Study of the Leipzig Center for Civilization Diseases (LIFE). This is a population-based study with a representative sample of people living in Leipzig, Germany, a city with about 550,000 inhabitants. The main aim of this study was to examine causes for the development of important civilization diseases. We obtained an ageand gender-stratified random selection of inhabitants, ranging in age from 18 to 80 years, from the local residents’ registration office. According to the study protocol, the focus was on the age group 40-80 years; the 18-39 years age range was included but underrepresented. Letters of invitation were sent out by mail. At the study center, the participants underwent a set of assessment batteries, including collection of their sociodemographic data, medical history, lifestyle factors, and several medical examinations. Pregnancy and insufficient command of the German language were exclusion criteria. Pregnancy was chosen as an exclusion criterion because the medical examinations might be too laborious for pregnant women. The participants received a total of 20 EUR to cover their travel expenses. Details of the study design are published elsewhere (Loeffler et al., 2015). The study was approved by the Ethics Committee of the University of Leipzig. Informed consent was obtained from all participants.
2.2.
Instruments
The GAD-7 (Spitzer et al., 2006) is a one-dimensional instrument designed to detect symptoms of generalized anxiety disorder as it is defined in the DSM-IV. The item scores range from 0 (not at all) to 3 (nearly every day), resulting in a sum score range from 0 to 21.
5 In addition to the GAD-7, the following well-established questionnaires were used: the Short Form Health Survey–8 SF-8, for measuring quality of life (Ware et al., 2001), the Multidimensional Fatigue Inventory MFI-20, for measuring fatigue (Smets et al., 1995), the Life Orientation Test LOT-R, for measuring dispositional optimism (Scheier et al., 1994), the Patient Health Questionnaire PHQ-15, for measuring physical complaints (Kroenke et al., 2002), the Pittsburgh Sleep Quality Index PSQI, for measuring sleep problems (Buysse et al., 1989), the Epworth Sleepiness Scale ESS, for measuring daytime sleepiness (Johns, 1991), the Satisfaction with Life Scale (Diener et al., 1985), and the ENRICHD Social Support Scale ESSI (Berkman et al., 2003). Alcohol consumption was assessed with regard to frequency and amount of different alcoholic beverages consumed within the last year, and tobacco use was assessed with questions about former and current smoking, smoking duration, and amounts of different tobacco products used. Sociodemographic factors were obtained in a structured interview.
2.3.
Statistical methods
Age and gender differences in GAD were tested with two-factorial ANOVAs, using the factors age group (five categories according to Table 1) and gender (two categories). Cronbach’s alpha coefficient was used to determine internal consistency. Effect sizes were calculated using Cohen’s d (Cohen, 1988), relating the mean score differences to the pooled standard deviation. Associations between the GAD-7 scores and other scales were expressed in terms of Pearson correlations. The effect of socioeconomic and behavioral factors on GAD7 was tested with three-factorial ANOVAs. In addition to the factor of interest, the factors age group and gender were included in these ANOVAs to account for these possible confounders. Socioeconomic status was calculated in accordance with the Robert-Koch-Institute’s GEDA examination (Lampert et al., 2013), which integrates education, income, and professional position into one index. For the regression analyses, socioeconomic status was categorized into three strata. Income was defined as household net income, divided by the weighted number of household members. The factorial structure was tested with exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). As criteria for measuring model fit, we used the comparative fit index (CFI), the Tucker-Lewis index (TLI), and the root mean square error of approximation (RMSEA) (Hu and Bentler, 1999). The χ² values are not considered as absolute fit indicators because of the large sample size. Measurement invariance across
6 gender and age groups was tested with three models. Model 1 assumed the same item-factor assignments across the groups (genders or age groups). Model 2 assumed these item-factor assignments and equivalent factor loadings across groups. Model 3 added equivalent intercepts to the specifications of Model 2. The calculations were performed with SPSS (Version 20) and AMOS (Version 5).
3.
Results
3.1.
Sample characteristics
The study included 10000 people. Details of the sampling procedure have been reported elsewhere (Loeffler et al., 2015). The response rate of the study was 33%. If only one GAD-7 item was missing, it was replaced with the rounded mean of the other items. Following this procedure, valid data were available for 9721 persons. Sociodemographic characteristics of this sample are given in Table 1.
3.2 GAD-7 mean scores
The mean scores of the GAD-7 are illustrated in Figure 1, separated by gender and age group. The females’ mean anxiety scores were higher than those of the males in all age groups. In each age category, the difference was roughly one unit. Figure 1 also shows that there was no linear age trend. Up to the age of 60 years we observe an increase, then a decrease, and from 65 years on once more an increase in anxiety. The ANOVA showed a very strong main effect of gender F = 161.8, p < 0.001. Age group was also a statistically significant but much weaker factor (F = 8.5, p < 0.001), while there was no statistically significant interaction between gender and age group (F = 0.7, p = 0.592).
Because of the lack of a substantial and systematic age trend, we present the normative scores (cumulative percentages) for males and females without separate analyses of age groups (Table 3). The percentage of people with GAD-7 scores above the cut-off 10+ was 5.9%. For the GAD-2 with the cut-off 3+, the percentage was 7.3%.
7 3.3 Psychometric analyses
The GAD-7 items are listed in Table 4, separately for males and females. The greatest gender differences were found for items 1 (feeling nervous) and 4 (trouble relaxing), while the gender difference was lowest for item 6 (easily annoyed or irritable). All items contributed positively to the total score with corrected item-total correlations of 0.50 and above. The internal consistency (Cronbach’s α) was 0.85. The first two items, out of which the GAD-2 is comprised, were among the items with the highest rit coefficients (0.67 and 0.69). The internal consistency of the GAD-2 was α = 0.72. The first two eigenvalues obtained in the exploratory factorial analysis were 3.77 and 0.77. This supports the one-dimensional solution. The first factor explained 53.9% of the total variance. Unidimensionality of the GAD-7 was also tested using CFA. All 7 items were specified as indicators of this factor. Multigroup CFA was used to test the model across gender and age groups. Model 1 assumed the same item-factor assignments across the groups. Model 2 assumed these item-factor assignments and equivalent factor loadings across groups. Model 3 added equivalent intercepts to the specifications of model 2. The results are given in Table 4. Taking the criteria together, Model 3 (equivalence in factor loadings and in intercepts) fitted the data best.
3.4. Correlations with other scales
The GAD-7 scores were most strongly correlated with the mental component MCS of the SF8, followed by physical complaints (PHQ-15) and fatigue (MFI), cf. Table 5. Additionally, anxiety was associated with physical quality of life, pessimism, sleep problems, lack of life satisfaction, lack of social support, and daytime sleepiness. All GAD-2 correlations with the other scales were somewhat lower than those of the GAD-7 (Table 5). The correlation between GAD-7 and GAD-2 was r = 0.87.
3.5. Associations with sociodemographic factors and behavioral factors
8 Table 6 presents anxiety mean scores for different subgroups, defined by sociodemographic and behavioral factors. The F and p values given in the first column of Table 6 refer to the impact of the sociodemographic or behavioral factor in the three-way ANOVA. All factors had a statistically significant influence on anxiety. Unemployed people reported markedly higher degrees of anxiety (M=4.27) than the other occupational status groups (M between 3.22 and 3.40). Anxiety was associated with low income, a low socioeconomic level, and smoking. It is interesting to note that when considering males and females separately, the alcohol drinkers reported somewhat higher anxiety levels than the non-drinkers (Table 6). However, in the combined analysis, when aggregated across both genders, the alcohol drinkers reported lower anxiety than the non-drinkers due to the confounding of gender and alcohol consumption.
4. Discussion
The GAD-7 proved to be a reliable instrument for measuring anxiety in the general population. The internal consistency (α = 0.85) was between the two previous German studies with α = 0.82 (Wild et al., 2014) and α = 0.89 (Löwe et al., 2008), indicating high reliability. CFA confirmed unidimensionality and measurement invariance across gender and age groups. In the previous normative study (Löwe et al., 2008) invariance was shown in terms of equivalent factor loadings. The study presented here adds equivalence of intercepts. All items contributed to the GAD-7 sum score with a similar amount. As was to be expected, women were more anxious than man. The gender difference (diff = 1.06) was between that reported in the previous German normative study (diff = 0.54) (Löwe et al., 2008) and that from the Canadian study (diff = 1.31) (Vasiliadis et al., 2015). The gender differences were nearly equal for all age groups (Figure 1), which is also expressed in the nonsignificant effect of the interaction between gender and age group in the ANOVA. Therefore, age and gender effects can be considered separately. There was no linear age trend. Anxiety mean scores increased slightly from the youngest group up to the 55-59 years group, followed by a decline up to the age range of 65-69 years, and finally a subsequent increase. One reason for the relatively low anxiety levels of persons between 65 and 69 years of age may be that many of them are old enough to be retired and thus relieved of work stress, but young enough to still be enjoying good health for the most part. In the Löwe et al. (2008) study the highest GAD-7 mean scores were also found for the age group
9 55-64 years with a subsequent decline (65-74 years) and an increase thereafter ( ≥ 75 years), which is similar to our results. Anxiety was most strongly correlated with the mental component of the SF-8, physical complaints, and fatigue. The high correlation between physical complaints (as measured with the PHQ-15) and anxiety shows that physical symptoms are relevant predictors of the general level of anxiety. Other studies also reported high correlations between anxiety and physical complaints. The correlation between PHQ-15 and GAD-7 in a sample of psychosomatic outpatients was 0.51 (Gierk et al., 2015) which is very similar to our results (r = 0.54). A Chinese study (Zhu et al., 2012) proved similar associations between HADS anxiety and physical complaints, expressed in PHQ-15 mean score differences of the HADS anxiety groups. However, causal conclusions for the relationship between anxiety and physical complaints are not possible with this cross-sectional study. It is also possible that a high level of anxiety leads to exaggerated symptom reporting. This study also provides psychometric properties of the ultra-short GAD-2. Its reliability (α = 0.72) is markedly lower than that of the GAD-7 but nevertheless acceptable. It confirms the reliability coefficient (α = 0.71) obtained in a previous study (Wild et al., 2014). All correlations with the other scales are lower for the GAD-2 compared with the GAD-7, but most of the differences were lower than 0.05. If clinicians are interested in screening for anxiety, the GAD-7 is preferable, but the GAD-2 can also be used to obtain a rough estimate of patients’ anxiety levels. About 50% of the respondents had the minimal GAD-2 score of 0; therefore, this instrument cannot differentiate within the less anxious half of the general population. Normative scores for the GAD-2 are given here for the first time. It is in line with other studies that anxiety levels are highest in people living separately, people with low income, and unemployed people, e.g., (Löwe et al., 2008). The GAD-7 mean score difference between the highest and the lowest household income groups (diff = 1.07) was nearly exactly as great as the difference between males and females (diff = 1.06), while the difference between the education groups was lower (diff = 0.46). One interesting finding is the association between anxiety and the behavioral variables alcohol consumption and cigarette smoking. While males who drink alcohol (> 20g/d) and smoke cigarettes were only marginally more anxious than males who do not drink and smoke excessively (diff = 0.20 for both variables), we observed large differences among the females (diff = 0.75 for excessive alcohol consumption and diff = 0.74 for smoking). The psychosocial backgrounds for smoking and alcohol drinking are obviously different for males and females. The higher degree of anxiety for smoking women compared with non-smoking
10 women is also in line with the UK Million Women Study (Liu et al., 2016), while alcohol consumption was not positively associated with anxiety in that study. Since a gold standard for diagnosing anxiety was not used in this study, we cannot directly contribute to the quest for an optimal cut-off. The original work defines four categories with three cut-offs: no (0-4), mild (5-9), moderate (10-14), and severe anxiety (≥ 15). Given the criterion 10+ adopted in the previous normative study (Löwe et al., 2008),
5.9% of the sample (4.2% of the males and 7.4% of the females) had heightened anxiety, which is very similar to the 6.0% seen in the normative study (Löwe et al., 2008). A score of 10 or above has been associated with a positive likelihood ratio for the presence of generalized anxiety disorder of 5.1 (Spitzer et al., 2006). According to the cut-off 8+, as recommended in a recent metaanalysis (Plummer et al., 2016), 11% of the general population are anxious according to our study; in the previous normative study (Löwe et al., 2008) this proportion is 12.1%. Although it might be confusing to add a further cut-off (8+) to the three already existing cut-offs (5+, 10+, 15+), 8+ seems to be a good alternative. Clinicians are advised to perform an extended diagnostic assessment for anxiety disorder when they encounter patients with GAD-7 scores in this range. For the GAD-2, the cut-off score 3+, recommended both by the original authors (Löwe et al., 2010) and the metaanalysis (Plummer et al., 2016), yielded a percentage of 7.3% of the general population showing heightened anxiety. Some limitations of this study should be considered. The response rate (33%) was low. Since we could not obtain socio-economic data from the non-participants, we cannot quantify the effect of non-representativeness. However, other large epidemiologic medical studies are also faced with this problem, in the large DEGS study the response rate was 42 % (ScheidtNave et al., 2012). Furthermore, the participants came from one community. The degree of generalizability to the whole country is difficult to assess. An urbane place of residence seems to be an only marginal predictor of anxiety in Germany (Daig et al., 2013), and several studies found no systematic differences in anxiety between East and West Germany. Therefore, we believe that there is no severe bias in generalizing the results. While the normative scores might be affected by non-representativeness to a certain degree, the calculations of the association between anxiety and the other variables are less vulnerable. It is difficult to assess the generalizability of the study results to other countries. For the quality of life questionnaire EORTC QLQ-C30 there were no systematic differences between Germany and other European countries in the normative values (Hinz et al., 2014), and the depression screener PHQ-9 yielded similar results in Germany (Löwe 2004) and the US (Kroenke 2001).
11 Therefore, we assume that it is unlikely that that the developed Western countries substantially differ in the distribution of the GAD-7 scores in the general population. However, according to a recent systematic review (Remes et al., 2016), the prevalence of anxiety disorders in Asian and African cultures is lower than that in Euro/Anglo cultures. Since our study did not include a standard criterion for anxiety, we cannot demonstrate the validity of the GAD-7 and the GAD-2 in terms of sensitivity and specificity analyses. However, the correlations between the GAD-7 scores and physical and mental components of quality of life, physical complaints, fatigue, habitual optimism and pessimism, satisfaction with life and sleep problems contribute to the construct validity of this instrument. Taken together, the study confirms the finding of the previous German normative study (Löwe et al., 2008) that the GAD-7 is an efficient, reliable and valid instrument for assessing generalized anxiety. If the aim of an investigation is to assess the individual degree of anxiety for a certain patient, the GAD-7 is to be preferred over the GAD-2. For studies with an epidemiologic objective the GAD-2 is a sufficient and economic alternative. While there were no linear age trends, gender differences must be taken into account when samples of patients with different gender distributions are compared. Additionally, the socioeconomic status is strongly associated with anxiety and should also be considered when comparisons among groups of patients are performed.
Competing interests The authors declare that they have no competing interests. Acknowledgements This publication is supported by LIFE - Leipzig Research Centre for Civilization Diseases, an organizational unit affiliated to the Medical faculty of the University of Leipzig. LIFE is funded by means of the European Union, by the European Regional Development Fund (ERDF) and by funds of the Free State of Saxony within the excellence initiative (project numbers 713-241202, 14505/2470, 14575/2470).
References Beard, C., Bjorgvinsson, T., 2014. Beyond generalized anxiety disorder: psychometric properties of the GAD-7 in a heterogeneous psychiatric sample. J. Anxiety Disord. 28, 547–552. Berkman, L.F., Blumenthal, J., Burg, M., Carney, R.M., Catellier, D., Cowan, M.J., Czajkowski, S.M., DeBusk, R., Hosking, J., Jaffe, A., Kaufmann, P.G., Mitchell, P.,
12 Norman, J., Powell, L.H., Raczynski, J.M., Schneiderman, N., 2003. Effects of treating depression and low-perceived social support on clinical events after myocardial infarction - The enhancing recovery in coronary heart disease patients (ENRICHD) randomized trial. JAMA 289, 3106–3116. Beutel, M.E., Glaesmer, H., Decker, O., Fischbeck, S., Brähler, E., 2009. Life satisfaction, distress, and resiliency across the life span of women. Menopause 16, 1132–1138. Beutel, M.E., Glaesmer, H., Wiltink, J., Marian, H., Brähler, E., 2010. Life satisfaction, anxiety, depression and resilience across the life span of men. Aging Male 13, 32–39. Buysse, D.J., Reynolds, C.F., Monk, T.H., Berman, S.R., Kupfer, D.J., 1989. The Pittsburgh Sleep Quality Index - A new instrument for psychiatric practice and research. Psychiatry Res. 28, 193–213. Cohen, J., 1988. Statistical power analysis for the behavioral sciences. Erlbaum, Hillsdale, NJ. Daig, I., Hinz, A., Spauschus, A., Decker, O., Brahler, E., 2013. Are urban dwellers more depressed and anxious than the rural population? Results of a representative survey. Psychother. Psychosom. Med. 63, 445–454. Diener, E., Emmons, R.A., Larsen, R.J., Griffin, S., 1985. The Satisfaction with Life Scale. J. Personality Assess. 49, 71–75. Donker, T., van Straten, A., Marks, I., Cuijpers, P., 2011. Quick and easy self-rating of Generalized Anxiety Disorder: validity of the Dutch web-based GAD-7, GAD-2 and GAD-SI. Psychiatry Res. 188, 58–64. García-Campayo, J., Zamorano, E., Ruiz, M.A., Pardo, A., Perez-Paramo, M., Lopez-Gomez, V., Freire, O., Rejas, J., 2010. Cultural adaptation into Spanish of the generalized anxiety disorder-7 (GAD-7) scale as a screening tool. Health Qual. Life Outcomes 8, 8. Gierk, B., Kohlmann, S., Toussaint, A., Wahl, I., Brünahl, C.A., Murray, A.M., Löwe, B. 2015. Assessing somatic symptom burden: A psychometric comparison of the Patient Health Questionnaire – 15 (PHQ-15) and the Somatic Symptom Scale – 8 (SSS-8). J. Psychosom. Res. 78, 352-355. Hinz, A., Singer, S., Brähler, E., 2014. European reference values for the quality of life questionnaire EORTC QLQ-C30: Results of a German investigation and a summarizing analysis of six European general population normative studies. Acta Oncol. 53, 958-965. Hu, L.T., Bentler, P.M., 1999. Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct. Equat. Modeling 6, 1–55. Johns, M.W., 1991. A new method for measuring daytime sleepiness - the Epworth Sleepiness Scale. Sleep 14, 540–545.
13 Konkan, R., Senormanci, Ö., Güclü, O., Aydin, R., Sungur, M.Z., 2013. Validity and reliability study for the Turkish adaptation of the Generalized Anxiety Disorder-7 (GAD7) Scale. Arch. Neuropsychiatry 50, 53–58. Kroenke, K., Spitzer, R.L., Williams, J.B.W., 2001. The PHQ-9 - Validity of a brief depression severity measure. J. Gen. Intern. Med. 16, 606–613. Kroenke, K., Spitzer, R.L., Williams, J.B.W., 2002. The PHQ-15: Validity of a new measure for evaluating the severity of somatic symptoms. Psychosom. Med. 64, 258–266. Kroenke, K., Spitzer, R.L., Williams, J.B.W., Monahan, P.O., Löwe, B., 2007. Anxiety disorders in primary care: prevalence, impairment, comorbidity, and detection. Ann. Internal Med. 146, 317–325. Kujanpaa, T., Ylisaukko-Oja, T., Jokelainen, J., Hirsikangas, S., Kanste, O., Kyngas, H., Timonen, M., 2014. Prevalence of anxiety disorders among Finnish primary care high utilizers and validation of Finnish translation of GAD-7 and GAD-2 screening tools. Scand. J. Prim. Health Care 32, 78–83. Lampert, T., Kroll, L., Mueters, S., Stolzenberg, H., 2013. Measurement of the socioeconomic status within the German Health Update 2009 (GEDA). BundesgesundheitsblattGesundheitsforschung-Gesundheitsschutz 56, 131–143. Liu, B., Floud, S., Pirie, K., Green, J., Peto, R., Beral, V., 2016. Does happiness itself directly affect mortality? The prospective UK Million Women Study. Lancet 387, 874-881. Loeffler, M., Engel, C., Ahnert, P., Alfermann, D., Arelin, K., Baber, R. et al., 2015. The LIFE-Adult-Study: objectives and design of a population-based cohort study with 10,000 deeply phenotyped adults in Germany. BMC Public Health 15, 691. Löwe, B., Decker, O., Müller, S., Brähler, E., Schellberg, D., Herzog, W., Herzberg, P.Y., 2008. Validation and standardization of the generalized anxiety disorder screener (GAD7) in the general population. Med. Care 46, 266–274. Löwe, B., Unützer, J., Callahan, C.M., Perkins, A.J., & Kroenke, K., 2004. Monitoring depression treatment outcomes with the Patient Health Questionnaire-9. Med. Care 42, 1194-1201. Löwe, B., Wahl, I., Rose, M., Spitzer, C., Glaesmer, H., Wingenfeld, K., Schneider, A., Brähler, E., 2010. A 4-item measure of depression and anxiety: Validation and standardization of the Patient Health Questionnaire-4 (PHQ-4) in the general population. J. Affect. Disord. 122, 86–95. McHugh, R.K., Rasmussen, J.L., Otto, M.W., 2011. Comprehension of self-report evidencebased measures of anxiety. Depress. Anxiety 28, 607–614.
14 Parmentier, H., Garcia-Campayo, J., Prieto, R., 2013. Comprehensive review of generalized anxiety disorder in primary care in Europe. Curr. Med. Res. Opin. 29, 355–367. Plummer, F., Manea, L., Trepel, D., McMillan, D., 2016. Screening for anxiety disorders with the GAD-7 and GAD-2: a systematic review and diagnostic metaanalysis. Gen. Hosp. Psychiatry 39, 24–31. Remes, O., Brayne, C., van der Linde, R., Lafortune, L., 2016. A systematic review of reviews on the prevalence of anxiety disorders in adult populations. Brain and Behavior 6, e00497. Ruiz, M.A., Zamorano, E., Garcia-Campayo, J., Pardo, A., Freire, O., Rejas, J., 2011. Validity of the GAD-7 scale as an outcome measure of disability in patients with generalized anxiety disorders in primary care. J. Affect. Disord. 128, 277–286. Schalet, B.D., Cook, K.F., Choi, S.W., Cella, D., 2014. Establishing a common metric for self-reported anxiety: Linking the MASQ, PANAS, and GAD-7 to PROMIS Anxiety. J. Anxiety Disord. 28, 88–96. Scheidt-Nave, C., Kamptsiuris, P., Gösswald, A., Hölling, H., Lange, M., Busch, M.A. et al., 2012. German health interview and examination survey for adults (DEGS) – design, objectives and implementation of the first data collection wave. BMC Public Health 12, 730. Scheier, M.F., Carver, C.S., Bridges, M.W., 1994. Distinguishing optimism from neuroticism (and trait anxiety, self-mastery, and self-esteem) - A reevaluation of the Life Orientation Test. J. Pers. Soc. Psychol. 67, 1063–1078. Seo, J.-G., Park, S.-P., 2015. Validation of the Generalized Anxiety Disorder-7 (GAD-7) and GAD-2 in patients with migraine. J. Headache Pain 16, 97. Smets, E.M.A., Garssen, B., Bonke, B., Dehaes, J.C.J.M., 1995. The Multidimensional Fatigue Inventory (MFI): Psychometric qualities of an instrument to assess fatigue. J. Psychosom. Res. 39, 315–325. Somers, J.M., Goldner, E.M., Waraich, P., Hsu, L., 2006. Prevalence and incidence studies of anxiety disorders: a systematic review of the literature. Can. J. Psychiat. 51, 100–113. Spitzer, R.L., Kroenke, K., Williams, J.B.W., Löwe, B., 2006. A brief measure for assessing generalized anxiety disorder - The GAD-7. Arch. Int. Med. 166, 1092–1097. Vasiliadis, H.-M., Chudzinski, V., Gontijo-Guerra, S., Preville, M., 2015. Screening instruments for a population of older adults: The 10-item Kessler Psychological Distress Scale (K10) and the 7-item Generalized Anxiety Disorder Scale (GAD-7). Psychiatry Res. 228, 89–94.
15 Ware, J.E., Kosinski, M., Dewey, J.E., Gandek, B., 2001. How to score and interpret singleitem health status measures: A manual for users of the SF-8TM Health Survey. QualityMetric Incorporated, Lincoln (RI). Wild, B., Eckl, A., Herzog, W., Niehoff, D., Lechner, S., Maatouk, I., Schellberg, D., Brenner, H., Müller, H., Löwe, B., 2014. Assessing generalized anxiety disorder in elderly people using the GAD-7 and GAD-2 scales: results of a validation study. Am. J. Geriatric Psychiatry 22, 1029–1038. Zhu, C., Ou, L., Geng, Q., Zhang, M., Ye, R., Chen, J., Jiang, W., 2012. Association of somatic symptoms with depression and anxiety in clinical patients of general hospitals in Guangzhou, China. Gen. Hosp. Psychiatry 34, 113-120.
Figure 1: GAD-7 mean scores, broken down by gender and age group.
Table 1. Sociodemographic characteristics of the sample Males (n=4615) n (%) Age Mean (SD) Age group 39 years 40-49 years 50-59 years 60-69 years 70 years Marital status Married, living together Married, living separately Never married Divorced Widowed Missing Education < 10 years 10-11 years 12 years Missing Occupational status Working full time Working part-time Unemployed Retired Other Missing Income < 1000 €
57.2 (12.7)
Females (n=5106) n (%) 56.2 (12.2)
Total sample (n=9721) n (%) 56.7 (12.4)
255 1205 1021 1170 964
(5.5) (26.1) (22.1) (25.4) (20.9)
257 1439 1230 1294 886
(5.0) (28.2) (24.1) (25.3) (17.4)
512 2644 2251 2464 1850
(5.3) (27.2) (23.2) (25.3) (19.0)
2962 101 907 525 113 7
(64.2) (2.2) (19.7) (11.4) (2.4) (0.2)
2854 132 830 813 468 9
(55.9) (2.6) (16.3) (15.9) (9.2) (0.2)
5816 233 1737 1338 581 16
(59.8) (2.4) (17.9) (13.7) (6.0) (0.2)
361 2488 1694 72
(7.8) (53.9) (36.7) (1.6)
396 3026 1618 66
(7.8) (59.3) (31.7) (1.3)
757 5514 3312 138
(7.8) (56.7) (34.1) (1.4)
2308 164 301 1734 68 40
(50.0) (3.6) (6.5) (37.6) (1.5) (0.9)
1975 751 307 1860 152 61
(38.7) (14.7) (6.0) (36.4) (3.0) (1.2)
4283 915 608 3594 220 101
(44.1) (9.4) (6.3) (37.0) (2.3) (1.0)
948
19.9
1896
36.2
2844
28.4
16 1000 - < 2000 € ≥ 2000 € Missing Socioeconomic level Low Medium High Missing Smoking Current nonsmoker Current smoker Missing Alcohol consumption < 20 g/day ≥ 20 g/day Missing
2337 1236 245
49.0 25.9 5.1
2297 784 257
43.9 15.0 4.9
4634 2020 502
46.3 20.2 5.0
889 2683 1031 12
(19.3) (58.1) (22.3) (0.3)
1047 3131 911 17
(20.5) (61.3) (17.8) (0.3)
1936 5814 1942 29
(19.9) (59.8) (20.0) (0.3)
3462 1072 81
(75.0) (23.2) (1.8)
3936 1007 163
(77.1) (19.7) (3.2)
7398 2079 244
(76.1) (21.4) (2.5)
2860 1439 316
(62.0) (31.2) 6.8)
4411 351 344
(86.4) (6.9) (6.7)
7271 1790 660
(74.8) (18.4) (6.8)
17 Table 2. Cumulative percentages of the GAD-7 and GAD-2 scores Score Males Females Total GAD-7 0 22.4 15.0 18.5 1 38,7 26.0 32.1 2 53.9 39.1 46.1 3 66.7 51.1 58.5 4 75.6 62.4 68.6 5 82.4 71.7 76.8 6 88.1 79.5 83.6 7 92.3 85.9 89.0 8 94.5 89.6 91.9 9 95.8 92.6 94.1 10 97.0 94.3 95.6 11 97.7 95.8 96.7 12 98.3 97.1 97.6 13 98.7 97.8 98.2 14 99.1 98.5 98.8 15 99.3 98.9 99.1 16 99.4 99.2 99.3 17 99.6 99.4 99.5 18 99.7 99.7 99.7 19 99.8 99.8 99.8 20 99.9 99.9 99.9 21 100.0 100.0 100.0 GAD-2 0 57.7 40.8 48.9 1 81.1 68.1 74.3 2 95.0 90.5 92.7 3 97.6 95.3 96.4 4 99.0 97.8 98.3 5 99.6 99.1 99.3 6 100.0 100.0 100.0
18 Table 3. GAD-7 component and global mean scores, sex differences, and item-total correlations 1. Feeling nervous 2. Not able to stop worrying 3. Worry about different things 4. Trouble relaxing 5. Being restless 6. Easily annoyed or irritable 7. Feeling afraid
Males M SD 0.41 0.61 0.30 0.56 0.49 0.65 0.57 0.68 0.39 0.64 0.61 0.63 0.24 0.52
Females M SD 0.64 0.71 0.44 0.66 0.65 0.70 0.81 0.78 0.50 0.72 0.65 0.64 0.36 0.61
Total M SD 0.53 0.68 0.37 0.62 0.57 0.68 0.70 0.74 0.45 0.69 0.63 0.63 0.31 0.57
GAD-2 sum score GAD-7 sum score
0.71 1.04 3.01 3.12
1.09 1.22 4.07 3.53
0.91 1.15 3.57 3.38
d(sex) 0.35 0.23 0.24 0.33 0.16 0.06 0.21
rit 0.67 0.69 0.68 0.66 0.52 0.52 0.60
0.33 α= 0.72 0.32 α= 0.85
19 Table 4. Fit indices for multigroup CFA Model Total model Gender Model 1: same item-factor assign. Model 2: Model 1 + equiv. factor loadings Model 3: Model 1 + equiv. factor loadings + equiv. intercepts Age groups Model 1: same item-factor assign Model 2: Model 1 + equiv. factor loadings Model 3: Model 1 + equiv. factor loadings + equiv. intercepts
χ² 517.5
df 14
χ²/df 37.0
CFI 0.970
TLI 0.954
RMSEA 0.085
193.9 208.0
28 35
6.93 5.94
0.954 0.952
0.931 0.942
0.064 0.059
217.9
42
5.19
0.951
0.951
0.054
1032.6 1166.7
70 98
14.7 11.9
0.960 0.956
0.940 0.952
0.039 0.034
1528.9
126
12.1
0.942
0.951
0.035
20 Table 5. Correlations with other scales PCS MCS Fatigue Opti- Pessi- Physical Sleep Daytime Life Social mism mism com- prob- Sleepi- satis- support plaints lems ness faction SF-8 SF-8 MFI LOT-R LOT-R PHQ-15 PSQI ESS SWLS ESSI 1. Feeling nervous 2. Not able to stop worrying 3. Worry about different things 4. Trouble relaxing 5. Being restless 6. Easily annoyed or irritable 7. Feeling afraid
-.18 -.21
-.59 -.58
.42 .44
-.22 -.27
.19 .26
.44 .40
.35 .33
.13 .14
-.33 -.37
-.20 -.23
-.20
-.55
.39
-.24
.26
.40
.34
.13
-.36
-.21
-.22 -.19 -.14
-.53 -.35 -.40
.42 .29 .31
-.22 -.16 -.17
.20 .21 .19
.45 .34 .33
.42 .29 .24
.15 .12 .18
-.34 -.22 -.23
-.22 -.17 -.17
-.21
-.50
.37
-.25
.28
.38
.30
.12
-.28
-.20
GAD-2 sum score GAD-7 sum score
-.22 -.26
-.66 -.68
.48 .52
-.27 -.30
.25 .31
.47 .54
.38 .45
.15 .19
-.39 -.42
-.24 -.27
21 Table 6. GAD-7 mean scores, broken down by sociodemographic and behavioral variables Males (n=4615) M SD Marital status (F=6.6, p<0.001) Married, living together Married, living separately Never married Divorced Widowed Education (F=22.2; p<0.01) 10 years 10-11 years 12 years Occupation (F=38.9, p<0.001) Working full time Working part-time Unemployed Retired Other Income (F=34.9, p<0.001) < 1000 € 1000 - < 2000 € ≥ 2000 € Socioeconomic level (F=34.9, p<0.001) Low Medium High Tobacco (F=13.0, p<0.001) Current nonsmoker Current smoker Alcohol (F=14.6, p<0.001) < 20 g/day ≥ 20 g/day
Females (n=5106) M SD
Total (n=9721) M SD
2.82 4.00 3.35 3.35 2.86
2.90 3.79 3.39 3.60 2.79
4.01 4.11 4.02 4.48 3.82
3.41 3.92 3.47 3.87 3.58
3.40 4.06 3.67 4.03 3.63
3.22 3.86 3.44 3.80 3.45
3.23 3.06 2.85
3.32 3.15 2.92
4.24 4.19 3.77
3.62 3.60 3.32
3.76 3.68 3.30
3.52 3.45 3.16
2.92 3.12 4.23 2.91 3.22
2.97 2.94 4.19 3.05 3.62
3.90 4.14 5.36 3.97 4.07
3.42 3.47 4.29 3.46 3.31
3.37 3.96 4.80 3.46 3.81
3.22 3.40 4.27 3.31 3.42
3.65 2.88 2.83
3.75 3.00 2.85
4.46 3.93 3.59
3.74 3.41 3.29
4.20 3.40 3.13
3.76 3.25 3.05
4.14 3.08 2.75
4.27 3.13 2.85
5.24 4.17 3.66
4.28 3.57 3.21
4.71 3.70 3.18
4.31 3.43 3.06
2.96 3.16
3.05 3.33
3.89 4.63
3.40 3.89
3.46 3.87
3.27 3.68
2.91 3.11
3.10 3.04
3.98 4.73
3.49 3.68
3.56 3.43
3.38 3.24
Highlights
- The study confirmed good psychometric properties of the GAD-7.
- The psychometric quality of the GAD-7 is superior to that of the ultra-short GAD-2.
- Women are more anxious than men, but there is no linear age trend in anxiety.
- Anxiety is associated with alcohol consumption and cigarette smoking, especially in women.
22
PII: DOI: Reference:
S0165-0327(16)31369-6 http://dx.doi.org/10.1016/j.jad.2016.12.012 JAD8673
To appear in: Journal of Affective Disorders Received date: 10 August 2016 Revised date: 11 November 2016 Accepted date: 16 December 2016 Cite this article as: Andreas Hinz, Annette M. Klein, Elmar Brähler, Heide Glaesmer, Tobias Luck, Steffi G. Riedel-Heller, Kerstin Wirkner and Anja Hilbert, Psychometric evaluation of the Generalized Anxiety Disorder Screener GAD-7, based on a large German general population sample, Journal of Affective Disorders, http://dx.doi.org/10.1016/j.jad.2016.12.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1 Psychometric evaluation of the Generalized Anxiety Disorder Screener GAD-7, based on a large German general population sample Andreas Hinz a*, Annette M. Klein b, Elmar Brähler a,c, Heide Glaesmer a, Tobias Luck d,e, Steffi G. Riedel-Heller d, Kerstin Wirkner e, Anja Hilbert f a
Department of Medical Psychology and Medical Sociology, University of Leipzig, Leipzig,
Germany b
Department of Child and Adolescent Psychiatry, Psychotherapy, and Psychosomatics ,
University of Leipzig, Leipzig, Germany c
Clinic for Psychosomatic Medicine and Psychotherapy, University Medical Center of the
Johannes Gutenberg University, 55131 Mainz, Germany. d
Institute of Social Medicine, Occupational Health, and Public Health, University of Leipzig,
Leipzig, Germany e
LIFE – Leipzig Research Center for Civilization Diseases, University of Leipzig, Leipzig,
Germany f
Leipzig University Medical Center, Integrated Research and Treatment Center Adiposity
Diseases, University of Leipzig, Leipzig Germany *
Corresponding author: Andreas Hinz, Department of Medical Psychology and Medical
Sociology, University of Leipzig, Philipp-Rosenthal-Str. 55, 04103 Leipzig, Germany. Phone: +49 341 9718820; Fax: +49 341 9718809. [email protected] Abstract Background: The Generalized Anxiety Disorder Scales GAD-7 and GAD-2 are instruments for the assessment of anxiety. The aims of this study are to test psychometric properties of these questionnaires, to provide normative values, and to investigate associations with sociodemographic factors, quality of life, psychological variables, and behavioral factors. Methods: A German community sample (n = 9721) with an age range of 18-80 years was surveyed using the GAD-7 and several other questionnaires. Results: Confirmatory factor analyses confirmed the unidimensionality and measurement invariance of the GAD-7 across age and gender. Females were more anxious than males (mean scores: M = 4.07 vs. M = 3.01; effect size: d = 0.33). There was no linear age trend. A total of 5.9 % fulfilled the cut-off criterion of 10 and above. Anxiety was correlated with
2 low quality of life, fatigue, low habitual optimism, physical complaints, sleep problems, low life satisfaction, low social support, low education, unemployment, and low income. Cigarette smoking and alcohol consumption were also associated with heightened anxiety, especially in women. When comparing the GAD-7 (7 items) with the ultra-short GAD-2 (2 items), the GAD-7 instrument was superior to the GAD-2 regarding several psychometric criteria.. Limitations: The response rate (33%) was low. Because of the cross-sectional character of the study, causal conclusions cannot be drawn. A further limitation is the lack of a gold standard for diagnosing anxiety. Conclusions: The GAD-7 can be recommended for use in clinical research and routine.
Keywords: Anxiety; General population; Epidemiology; Normative values
1. Introduction
Generalized anxiety disorder (GAD) is one of the most common mental disorders (Remes et al., 2016; Somers et al., 2006). Its lifetime prevalence is estimated to be 6.2 % (Somers et al., 2006), and it often remains undetected by physicians (Parmentier et al., 2013). Therefore, several screening instruments have been developed for effectively identifying patients with GAD (Kroenke et al., 2007; McHugh et al., 2011). One of these instruments is the Generalized Anxiety Disorder Scale GAD-7, developed by Spitzer and colleagues (Spitzer et al., 2006). This questionnaire indicates the presence of symptoms of GAD referred to in the DSM-IV. While in the DSM-5 the anxiety disorder spectrum was rearranged into separate groupings for the ‘classical’ anxiety disorders, trauma- and stressor-related disorders, obsessive-compulsive and related disorders, and dissociative disorders, the criteria for GAD did not change significantly as compared with DSM-IV. The GADS-7 has been translated into several languages and validated in multiple studies, e. g., (Beard and Bjorgvinsson, 2014; Seo and Park, 2015; Plummer et al., 2016). Normative values of a questionnaire are essential for assessing individuals’ and groups of patients’ level of burden. While it is common for well-established questionnaires to be tested in multiple normative studies, the research literature on normative values of the GAD-7 is very limited. There is only one large normative examination of adult people from the general population (Löwe et al., 2008). This study confirmed age and gender factorial
3 invariance of the GAD-7 factor structure. Detailed analyses of this data set have been published separately for men (Beutel et al., 2010) and women (Beutel et al., 2009). Two new studies with general population samples from Germany (Wild et al., 2014) and Canada (Vasiliadis et al., 2015) were recently performed with elderly people. Several studies examining patients with anxiety disorders used controls without such disorders (Ruiz et al., 2011; Konkan et al., 2013), but their sample sizes were low. There is considerable heterogeneity in the GAD-7 mean scores of the examinations of people from the general population, with values ranging from 2.0 (Wild et al., 2014) to 8.0 (Donker et al., 2011), which underlines the necessity of providing sound normative values. Females are more anxious than males, but these gender differences were also not identical across studies. Those difference scores ranged from 0.54 (Löwe et al., 2008) to 1.31 (Vasiliadis et al., 2015). There were also small and nonlinear age differences in these examinations. Validation studies identified different optimal cut-off scores for detecting GAD, ranging from 5 to 12 (Schalet et al., 2014; Vasiliadis et al., 2015; Kujanpaa et al., 2014; García-Campayo et al., 2010; Donker et al., 2011; Plummer et al., 2016). According to the original cut-off, 10 and above (10+), 6% of the sample from the normative study (Löwe et al., 2008) showed heightened levels of anxiety. Anxiety as measured with the GAD-7 proved to be strongly associated with depression with r = 0.71 (García-Campayo et al., 2010), r = 0.70 (Wild et al., 2014), and r = 0.64 (Löwe et al., 2008). In addition, GAD-7 anxiety was correlated with physical complaints (r = 0.51) (Gierk et al., 2015), headache (r = 0.40) (Seo & Park, 2015), disability (r = 0.70) (García-Campayo et al., 2010), lack of self esteem (r = -0.43) (Löwe et al., 2008), and lack of life satisfaction (r = -0.34) (Löwe et al., 2008). These studies differed with regard to the samples (general population or patients), age and gender distribution, sample size, and country. Therefore, the correlations cannot be directly compared with one another. In our study we used several questionnaires covering quality of life, life satisfaction, fatigue, optimism, physical complaints, sleep problems, and social support to specify the magnitude of the association with anxiety in a comparable way. In addition, we intended to investigate the associations with socioeconomic factors (education, occupational status, and income) as well as behavioral factors (smoking and alcohol intake). The GAD-2 is an ultra-short GAD questionnaire. It consists of the two psychometrically best items from the GAD-7. This GAD-2 is also part of the Patient Health Questionnaire-4 (PHQ-4) (Löwe et al., 2010), which additionally contains two depression items from the PHQ-9 (Kroenke et al., 2001). The cut-off 3+ was found to be optimal for the GAD-2 (Plummer et al., 2016). It is likely that the psychometric properties of a 2-item-
4 instrument will not be as good as those of an instrument with 7 items. However, the difference in psychometric accuracy between the GAD-7 and the GAD-2 has not been systematically tested yet. The aims of this study were - to analyze age and gender differences in anxiety, measured with the GAD-7 and the GAD-2, - to test psychometric properties of the GAD-7 and the GAD-2, including calculations of measurement equivalence and convergent validity, and - to test the associations between anxiety sociodemographic factors, quality of life, psychological variables, and behavioral factors, based on a large sample of the general population.
2.1.
Sample
Data were derived from the LIFE-Adult-Study of the Leipzig Center for Civilization Diseases (LIFE). This is a population-based study with a representative sample of people living in Leipzig, Germany, a city with about 550,000 inhabitants. The main aim of this study was to examine causes for the development of important civilization diseases. We obtained an ageand gender-stratified random selection of inhabitants, ranging in age from 18 to 80 years, from the local residents’ registration office. According to the study protocol, the focus was on the age group 40-80 years; the 18-39 years age range was included but underrepresented. Letters of invitation were sent out by mail. At the study center, the participants underwent a set of assessment batteries, including collection of their sociodemographic data, medical history, lifestyle factors, and several medical examinations. Pregnancy and insufficient command of the German language were exclusion criteria. Pregnancy was chosen as an exclusion criterion because the medical examinations might be too laborious for pregnant women. The participants received a total of 20 EUR to cover their travel expenses. Details of the study design are published elsewhere (Loeffler et al., 2015). The study was approved by the Ethics Committee of the University of Leipzig. Informed consent was obtained from all participants.
2.2.
Instruments
The GAD-7 (Spitzer et al., 2006) is a one-dimensional instrument designed to detect symptoms of generalized anxiety disorder as it is defined in the DSM-IV. The item scores range from 0 (not at all) to 3 (nearly every day), resulting in a sum score range from 0 to 21.
5 In addition to the GAD-7, the following well-established questionnaires were used: the Short Form Health Survey–8 SF-8, for measuring quality of life (Ware et al., 2001), the Multidimensional Fatigue Inventory MFI-20, for measuring fatigue (Smets et al., 1995), the Life Orientation Test LOT-R, for measuring dispositional optimism (Scheier et al., 1994), the Patient Health Questionnaire PHQ-15, for measuring physical complaints (Kroenke et al., 2002), the Pittsburgh Sleep Quality Index PSQI, for measuring sleep problems (Buysse et al., 1989), the Epworth Sleepiness Scale ESS, for measuring daytime sleepiness (Johns, 1991), the Satisfaction with Life Scale (Diener et al., 1985), and the ENRICHD Social Support Scale ESSI (Berkman et al., 2003). Alcohol consumption was assessed with regard to frequency and amount of different alcoholic beverages consumed within the last year, and tobacco use was assessed with questions about former and current smoking, smoking duration, and amounts of different tobacco products used. Sociodemographic factors were obtained in a structured interview.
2.3.
Statistical methods
Age and gender differences in GAD were tested with two-factorial ANOVAs, using the factors age group (five categories according to Table 1) and gender (two categories). Cronbach’s alpha coefficient was used to determine internal consistency. Effect sizes were calculated using Cohen’s d (Cohen, 1988), relating the mean score differences to the pooled standard deviation. Associations between the GAD-7 scores and other scales were expressed in terms of Pearson correlations. The effect of socioeconomic and behavioral factors on GAD7 was tested with three-factorial ANOVAs. In addition to the factor of interest, the factors age group and gender were included in these ANOVAs to account for these possible confounders. Socioeconomic status was calculated in accordance with the Robert-Koch-Institute’s GEDA examination (Lampert et al., 2013), which integrates education, income, and professional position into one index. For the regression analyses, socioeconomic status was categorized into three strata. Income was defined as household net income, divided by the weighted number of household members. The factorial structure was tested with exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). As criteria for measuring model fit, we used the comparative fit index (CFI), the Tucker-Lewis index (TLI), and the root mean square error of approximation (RMSEA) (Hu and Bentler, 1999). The χ² values are not considered as absolute fit indicators because of the large sample size. Measurement invariance across
6 gender and age groups was tested with three models. Model 1 assumed the same item-factor assignments across the groups (genders or age groups). Model 2 assumed these item-factor assignments and equivalent factor loadings across groups. Model 3 added equivalent intercepts to the specifications of Model 2. The calculations were performed with SPSS (Version 20) and AMOS (Version 5).
3.
Results
3.1.
Sample characteristics
The study included 10000 people. Details of the sampling procedure have been reported elsewhere (Loeffler et al., 2015). The response rate of the study was 33%. If only one GAD-7 item was missing, it was replaced with the rounded mean of the other items. Following this procedure, valid data were available for 9721 persons. Sociodemographic characteristics of this sample are given in Table 1.
3.2 GAD-7 mean scores
The mean scores of the GAD-7 are illustrated in Figure 1, separated by gender and age group. The females’ mean anxiety scores were higher than those of the males in all age groups. In each age category, the difference was roughly one unit. Figure 1 also shows that there was no linear age trend. Up to the age of 60 years we observe an increase, then a decrease, and from 65 years on once more an increase in anxiety. The ANOVA showed a very strong main effect of gender F = 161.8, p < 0.001. Age group was also a statistically significant but much weaker factor (F = 8.5, p < 0.001), while there was no statistically significant interaction between gender and age group (F = 0.7, p = 0.592).
Because of the lack of a substantial and systematic age trend, we present the normative scores (cumulative percentages) for males and females without separate analyses of age groups (Table 3). The percentage of people with GAD-7 scores above the cut-off 10+ was 5.9%. For the GAD-2 with the cut-off 3+, the percentage was 7.3%.
7 3.3 Psychometric analyses
The GAD-7 items are listed in Table 4, separately for males and females. The greatest gender differences were found for items 1 (feeling nervous) and 4 (trouble relaxing), while the gender difference was lowest for item 6 (easily annoyed or irritable). All items contributed positively to the total score with corrected item-total correlations of 0.50 and above. The internal consistency (Cronbach’s α) was 0.85. The first two items, out of which the GAD-2 is comprised, were among the items with the highest rit coefficients (0.67 and 0.69). The internal consistency of the GAD-2 was α = 0.72. The first two eigenvalues obtained in the exploratory factorial analysis were 3.77 and 0.77. This supports the one-dimensional solution. The first factor explained 53.9% of the total variance. Unidimensionality of the GAD-7 was also tested using CFA. All 7 items were specified as indicators of this factor. Multigroup CFA was used to test the model across gender and age groups. Model 1 assumed the same item-factor assignments across the groups. Model 2 assumed these item-factor assignments and equivalent factor loadings across groups. Model 3 added equivalent intercepts to the specifications of model 2. The results are given in Table 4. Taking the criteria together, Model 3 (equivalence in factor loadings and in intercepts) fitted the data best.
3.4. Correlations with other scales
The GAD-7 scores were most strongly correlated with the mental component MCS of the SF8, followed by physical complaints (PHQ-15) and fatigue (MFI), cf. Table 5. Additionally, anxiety was associated with physical quality of life, pessimism, sleep problems, lack of life satisfaction, lack of social support, and daytime sleepiness. All GAD-2 correlations with the other scales were somewhat lower than those of the GAD-7 (Table 5). The correlation between GAD-7 and GAD-2 was r = 0.87.
3.5. Associations with sociodemographic factors and behavioral factors
8 Table 6 presents anxiety mean scores for different subgroups, defined by sociodemographic and behavioral factors. The F and p values given in the first column of Table 6 refer to the impact of the sociodemographic or behavioral factor in the three-way ANOVA. All factors had a statistically significant influence on anxiety. Unemployed people reported markedly higher degrees of anxiety (M=4.27) than the other occupational status groups (M between 3.22 and 3.40). Anxiety was associated with low income, a low socioeconomic level, and smoking. It is interesting to note that when considering males and females separately, the alcohol drinkers reported somewhat higher anxiety levels than the non-drinkers (Table 6). However, in the combined analysis, when aggregated across both genders, the alcohol drinkers reported lower anxiety than the non-drinkers due to the confounding of gender and alcohol consumption.
4. Discussion
The GAD-7 proved to be a reliable instrument for measuring anxiety in the general population. The internal consistency (α = 0.85) was between the two previous German studies with α = 0.82 (Wild et al., 2014) and α = 0.89 (Löwe et al., 2008), indicating high reliability. CFA confirmed unidimensionality and measurement invariance across gender and age groups. In the previous normative study (Löwe et al., 2008) invariance was shown in terms of equivalent factor loadings. The study presented here adds equivalence of intercepts. All items contributed to the GAD-7 sum score with a similar amount. As was to be expected, women were more anxious than man. The gender difference (diff = 1.06) was between that reported in the previous German normative study (diff = 0.54) (Löwe et al., 2008) and that from the Canadian study (diff = 1.31) (Vasiliadis et al., 2015). The gender differences were nearly equal for all age groups (Figure 1), which is also expressed in the nonsignificant effect of the interaction between gender and age group in the ANOVA. Therefore, age and gender effects can be considered separately. There was no linear age trend. Anxiety mean scores increased slightly from the youngest group up to the 55-59 years group, followed by a decline up to the age range of 65-69 years, and finally a subsequent increase. One reason for the relatively low anxiety levels of persons between 65 and 69 years of age may be that many of them are old enough to be retired and thus relieved of work stress, but young enough to still be enjoying good health for the most part. In the Löwe et al. (2008) study the highest GAD-7 mean scores were also found for the age group
9 55-64 years with a subsequent decline (65-74 years) and an increase thereafter ( ≥ 75 years), which is similar to our results. Anxiety was most strongly correlated with the mental component of the SF-8, physical complaints, and fatigue. The high correlation between physical complaints (as measured with the PHQ-15) and anxiety shows that physical symptoms are relevant predictors of the general level of anxiety. Other studies also reported high correlations between anxiety and physical complaints. The correlation between PHQ-15 and GAD-7 in a sample of psychosomatic outpatients was 0.51 (Gierk et al., 2015) which is very similar to our results (r = 0.54). A Chinese study (Zhu et al., 2012) proved similar associations between HADS anxiety and physical complaints, expressed in PHQ-15 mean score differences of the HADS anxiety groups. However, causal conclusions for the relationship between anxiety and physical complaints are not possible with this cross-sectional study. It is also possible that a high level of anxiety leads to exaggerated symptom reporting. This study also provides psychometric properties of the ultra-short GAD-2. Its reliability (α = 0.72) is markedly lower than that of the GAD-7 but nevertheless acceptable. It confirms the reliability coefficient (α = 0.71) obtained in a previous study (Wild et al., 2014). All correlations with the other scales are lower for the GAD-2 compared with the GAD-7, but most of the differences were lower than 0.05. If clinicians are interested in screening for anxiety, the GAD-7 is preferable, but the GAD-2 can also be used to obtain a rough estimate of patients’ anxiety levels. About 50% of the respondents had the minimal GAD-2 score of 0; therefore, this instrument cannot differentiate within the less anxious half of the general population. Normative scores for the GAD-2 are given here for the first time. It is in line with other studies that anxiety levels are highest in people living separately, people with low income, and unemployed people, e.g., (Löwe et al., 2008). The GAD-7 mean score difference between the highest and the lowest household income groups (diff = 1.07) was nearly exactly as great as the difference between males and females (diff = 1.06), while the difference between the education groups was lower (diff = 0.46). One interesting finding is the association between anxiety and the behavioral variables alcohol consumption and cigarette smoking. While males who drink alcohol (> 20g/d) and smoke cigarettes were only marginally more anxious than males who do not drink and smoke excessively (diff = 0.20 for both variables), we observed large differences among the females (diff = 0.75 for excessive alcohol consumption and diff = 0.74 for smoking). The psychosocial backgrounds for smoking and alcohol drinking are obviously different for males and females. The higher degree of anxiety for smoking women compared with non-smoking
10 women is also in line with the UK Million Women Study (Liu et al., 2016), while alcohol consumption was not positively associated with anxiety in that study. Since a gold standard for diagnosing anxiety was not used in this study, we cannot directly contribute to the quest for an optimal cut-off. The original work defines four categories with three cut-offs: no (0-4), mild (5-9), moderate (10-14), and severe anxiety (≥ 15). Given the criterion 10+ adopted in the previous normative study (Löwe et al., 2008),
5.9% of the sample (4.2% of the males and 7.4% of the females) had heightened anxiety, which is very similar to the 6.0% seen in the normative study (Löwe et al., 2008). A score of 10 or above has been associated with a positive likelihood ratio for the presence of generalized anxiety disorder of 5.1 (Spitzer et al., 2006). According to the cut-off 8+, as recommended in a recent metaanalysis (Plummer et al., 2016), 11% of the general population are anxious according to our study; in the previous normative study (Löwe et al., 2008) this proportion is 12.1%. Although it might be confusing to add a further cut-off (8+) to the three already existing cut-offs (5+, 10+, 15+), 8+ seems to be a good alternative. Clinicians are advised to perform an extended diagnostic assessment for anxiety disorder when they encounter patients with GAD-7 scores in this range. For the GAD-2, the cut-off score 3+, recommended both by the original authors (Löwe et al., 2010) and the metaanalysis (Plummer et al., 2016), yielded a percentage of 7.3% of the general population showing heightened anxiety. Some limitations of this study should be considered. The response rate (33%) was low. Since we could not obtain socio-economic data from the non-participants, we cannot quantify the effect of non-representativeness. However, other large epidemiologic medical studies are also faced with this problem, in the large DEGS study the response rate was 42 % (ScheidtNave et al., 2012). Furthermore, the participants came from one community. The degree of generalizability to the whole country is difficult to assess. An urbane place of residence seems to be an only marginal predictor of anxiety in Germany (Daig et al., 2013), and several studies found no systematic differences in anxiety between East and West Germany. Therefore, we believe that there is no severe bias in generalizing the results. While the normative scores might be affected by non-representativeness to a certain degree, the calculations of the association between anxiety and the other variables are less vulnerable. It is difficult to assess the generalizability of the study results to other countries. For the quality of life questionnaire EORTC QLQ-C30 there were no systematic differences between Germany and other European countries in the normative values (Hinz et al., 2014), and the depression screener PHQ-9 yielded similar results in Germany (Löwe 2004) and the US (Kroenke 2001).
11 Therefore, we assume that it is unlikely that that the developed Western countries substantially differ in the distribution of the GAD-7 scores in the general population. However, according to a recent systematic review (Remes et al., 2016), the prevalence of anxiety disorders in Asian and African cultures is lower than that in Euro/Anglo cultures. Since our study did not include a standard criterion for anxiety, we cannot demonstrate the validity of the GAD-7 and the GAD-2 in terms of sensitivity and specificity analyses. However, the correlations between the GAD-7 scores and physical and mental components of quality of life, physical complaints, fatigue, habitual optimism and pessimism, satisfaction with life and sleep problems contribute to the construct validity of this instrument. Taken together, the study confirms the finding of the previous German normative study (Löwe et al., 2008) that the GAD-7 is an efficient, reliable and valid instrument for assessing generalized anxiety. If the aim of an investigation is to assess the individual degree of anxiety for a certain patient, the GAD-7 is to be preferred over the GAD-2. For studies with an epidemiologic objective the GAD-2 is a sufficient and economic alternative. While there were no linear age trends, gender differences must be taken into account when samples of patients with different gender distributions are compared. Additionally, the socioeconomic status is strongly associated with anxiety and should also be considered when comparisons among groups of patients are performed.
Competing interests The authors declare that they have no competing interests. Acknowledgements This publication is supported by LIFE - Leipzig Research Centre for Civilization Diseases, an organizational unit affiliated to the Medical faculty of the University of Leipzig. LIFE is funded by means of the European Union, by the European Regional Development Fund (ERDF) and by funds of the Free State of Saxony within the excellence initiative (project numbers 713-241202, 14505/2470, 14575/2470).
References Beard, C., Bjorgvinsson, T., 2014. Beyond generalized anxiety disorder: psychometric properties of the GAD-7 in a heterogeneous psychiatric sample. J. Anxiety Disord. 28, 547–552. Berkman, L.F., Blumenthal, J., Burg, M., Carney, R.M., Catellier, D., Cowan, M.J., Czajkowski, S.M., DeBusk, R., Hosking, J., Jaffe, A., Kaufmann, P.G., Mitchell, P.,
12 Norman, J., Powell, L.H., Raczynski, J.M., Schneiderman, N., 2003. Effects of treating depression and low-perceived social support on clinical events after myocardial infarction - The enhancing recovery in coronary heart disease patients (ENRICHD) randomized trial. JAMA 289, 3106–3116. Beutel, M.E., Glaesmer, H., Decker, O., Fischbeck, S., Brähler, E., 2009. Life satisfaction, distress, and resiliency across the life span of women. Menopause 16, 1132–1138. Beutel, M.E., Glaesmer, H., Wiltink, J., Marian, H., Brähler, E., 2010. Life satisfaction, anxiety, depression and resilience across the life span of men. Aging Male 13, 32–39. Buysse, D.J., Reynolds, C.F., Monk, T.H., Berman, S.R., Kupfer, D.J., 1989. The Pittsburgh Sleep Quality Index - A new instrument for psychiatric practice and research. Psychiatry Res. 28, 193–213. Cohen, J., 1988. Statistical power analysis for the behavioral sciences. Erlbaum, Hillsdale, NJ. Daig, I., Hinz, A., Spauschus, A., Decker, O., Brahler, E., 2013. Are urban dwellers more depressed and anxious than the rural population? Results of a representative survey. Psychother. Psychosom. Med. 63, 445–454. Diener, E., Emmons, R.A., Larsen, R.J., Griffin, S., 1985. The Satisfaction with Life Scale. J. Personality Assess. 49, 71–75. Donker, T., van Straten, A., Marks, I., Cuijpers, P., 2011. Quick and easy self-rating of Generalized Anxiety Disorder: validity of the Dutch web-based GAD-7, GAD-2 and GAD-SI. Psychiatry Res. 188, 58–64. García-Campayo, J., Zamorano, E., Ruiz, M.A., Pardo, A., Perez-Paramo, M., Lopez-Gomez, V., Freire, O., Rejas, J., 2010. Cultural adaptation into Spanish of the generalized anxiety disorder-7 (GAD-7) scale as a screening tool. Health Qual. Life Outcomes 8, 8. Gierk, B., Kohlmann, S., Toussaint, A., Wahl, I., Brünahl, C.A., Murray, A.M., Löwe, B. 2015. Assessing somatic symptom burden: A psychometric comparison of the Patient Health Questionnaire – 15 (PHQ-15) and the Somatic Symptom Scale – 8 (SSS-8). J. Psychosom. Res. 78, 352-355. Hinz, A., Singer, S., Brähler, E., 2014. European reference values for the quality of life questionnaire EORTC QLQ-C30: Results of a German investigation and a summarizing analysis of six European general population normative studies. Acta Oncol. 53, 958-965. Hu, L.T., Bentler, P.M., 1999. Cutoff criteria for fit indexes in covariance structure analysis: conventional criteria versus new alternatives. Struct. Equat. Modeling 6, 1–55. Johns, M.W., 1991. A new method for measuring daytime sleepiness - the Epworth Sleepiness Scale. Sleep 14, 540–545.
13 Konkan, R., Senormanci, Ö., Güclü, O., Aydin, R., Sungur, M.Z., 2013. Validity and reliability study for the Turkish adaptation of the Generalized Anxiety Disorder-7 (GAD7) Scale. Arch. Neuropsychiatry 50, 53–58. Kroenke, K., Spitzer, R.L., Williams, J.B.W., 2001. The PHQ-9 - Validity of a brief depression severity measure. J. Gen. Intern. Med. 16, 606–613. Kroenke, K., Spitzer, R.L., Williams, J.B.W., 2002. The PHQ-15: Validity of a new measure for evaluating the severity of somatic symptoms. Psychosom. Med. 64, 258–266. Kroenke, K., Spitzer, R.L., Williams, J.B.W., Monahan, P.O., Löwe, B., 2007. Anxiety disorders in primary care: prevalence, impairment, comorbidity, and detection. Ann. Internal Med. 146, 317–325. Kujanpaa, T., Ylisaukko-Oja, T., Jokelainen, J., Hirsikangas, S., Kanste, O., Kyngas, H., Timonen, M., 2014. Prevalence of anxiety disorders among Finnish primary care high utilizers and validation of Finnish translation of GAD-7 and GAD-2 screening tools. Scand. J. Prim. Health Care 32, 78–83. Lampert, T., Kroll, L., Mueters, S., Stolzenberg, H., 2013. Measurement of the socioeconomic status within the German Health Update 2009 (GEDA). BundesgesundheitsblattGesundheitsforschung-Gesundheitsschutz 56, 131–143. Liu, B., Floud, S., Pirie, K., Green, J., Peto, R., Beral, V., 2016. Does happiness itself directly affect mortality? The prospective UK Million Women Study. Lancet 387, 874-881. Loeffler, M., Engel, C., Ahnert, P., Alfermann, D., Arelin, K., Baber, R. et al., 2015. The LIFE-Adult-Study: objectives and design of a population-based cohort study with 10,000 deeply phenotyped adults in Germany. BMC Public Health 15, 691. Löwe, B., Decker, O., Müller, S., Brähler, E., Schellberg, D., Herzog, W., Herzberg, P.Y., 2008. Validation and standardization of the generalized anxiety disorder screener (GAD7) in the general population. Med. Care 46, 266–274. Löwe, B., Unützer, J., Callahan, C.M., Perkins, A.J., & Kroenke, K., 2004. Monitoring depression treatment outcomes with the Patient Health Questionnaire-9. Med. Care 42, 1194-1201. Löwe, B., Wahl, I., Rose, M., Spitzer, C., Glaesmer, H., Wingenfeld, K., Schneider, A., Brähler, E., 2010. A 4-item measure of depression and anxiety: Validation and standardization of the Patient Health Questionnaire-4 (PHQ-4) in the general population. J. Affect. Disord. 122, 86–95. McHugh, R.K., Rasmussen, J.L., Otto, M.W., 2011. Comprehension of self-report evidencebased measures of anxiety. Depress. Anxiety 28, 607–614.
14 Parmentier, H., Garcia-Campayo, J., Prieto, R., 2013. Comprehensive review of generalized anxiety disorder in primary care in Europe. Curr. Med. Res. Opin. 29, 355–367. Plummer, F., Manea, L., Trepel, D., McMillan, D., 2016. Screening for anxiety disorders with the GAD-7 and GAD-2: a systematic review and diagnostic metaanalysis. Gen. Hosp. Psychiatry 39, 24–31. Remes, O., Brayne, C., van der Linde, R., Lafortune, L., 2016. A systematic review of reviews on the prevalence of anxiety disorders in adult populations. Brain and Behavior 6, e00497. Ruiz, M.A., Zamorano, E., Garcia-Campayo, J., Pardo, A., Freire, O., Rejas, J., 2011. Validity of the GAD-7 scale as an outcome measure of disability in patients with generalized anxiety disorders in primary care. J. Affect. Disord. 128, 277–286. Schalet, B.D., Cook, K.F., Choi, S.W., Cella, D., 2014. Establishing a common metric for self-reported anxiety: Linking the MASQ, PANAS, and GAD-7 to PROMIS Anxiety. J. Anxiety Disord. 28, 88–96. Scheidt-Nave, C., Kamptsiuris, P., Gösswald, A., Hölling, H., Lange, M., Busch, M.A. et al., 2012. German health interview and examination survey for adults (DEGS) – design, objectives and implementation of the first data collection wave. BMC Public Health 12, 730. Scheier, M.F., Carver, C.S., Bridges, M.W., 1994. Distinguishing optimism from neuroticism (and trait anxiety, self-mastery, and self-esteem) - A reevaluation of the Life Orientation Test. J. Pers. Soc. Psychol. 67, 1063–1078. Seo, J.-G., Park, S.-P., 2015. Validation of the Generalized Anxiety Disorder-7 (GAD-7) and GAD-2 in patients with migraine. J. Headache Pain 16, 97. Smets, E.M.A., Garssen, B., Bonke, B., Dehaes, J.C.J.M., 1995. The Multidimensional Fatigue Inventory (MFI): Psychometric qualities of an instrument to assess fatigue. J. Psychosom. Res. 39, 315–325. Somers, J.M., Goldner, E.M., Waraich, P., Hsu, L., 2006. Prevalence and incidence studies of anxiety disorders: a systematic review of the literature. Can. J. Psychiat. 51, 100–113. Spitzer, R.L., Kroenke, K., Williams, J.B.W., Löwe, B., 2006. A brief measure for assessing generalized anxiety disorder - The GAD-7. Arch. Int. Med. 166, 1092–1097. Vasiliadis, H.-M., Chudzinski, V., Gontijo-Guerra, S., Preville, M., 2015. Screening instruments for a population of older adults: The 10-item Kessler Psychological Distress Scale (K10) and the 7-item Generalized Anxiety Disorder Scale (GAD-7). Psychiatry Res. 228, 89–94.
15 Ware, J.E., Kosinski, M., Dewey, J.E., Gandek, B., 2001. How to score and interpret singleitem health status measures: A manual for users of the SF-8TM Health Survey. QualityMetric Incorporated, Lincoln (RI). Wild, B., Eckl, A., Herzog, W., Niehoff, D., Lechner, S., Maatouk, I., Schellberg, D., Brenner, H., Müller, H., Löwe, B., 2014. Assessing generalized anxiety disorder in elderly people using the GAD-7 and GAD-2 scales: results of a validation study. Am. J. Geriatric Psychiatry 22, 1029–1038. Zhu, C., Ou, L., Geng, Q., Zhang, M., Ye, R., Chen, J., Jiang, W., 2012. Association of somatic symptoms with depression and anxiety in clinical patients of general hospitals in Guangzhou, China. Gen. Hosp. Psychiatry 34, 113-120.
Figure 1: GAD-7 mean scores, broken down by gender and age group.
Table 1. Sociodemographic characteristics of the sample Males (n=4615) n (%) Age Mean (SD) Age group 39 years 40-49 years 50-59 years 60-69 years 70 years Marital status Married, living together Married, living separately Never married Divorced Widowed Missing Education < 10 years 10-11 years 12 years Missing Occupational status Working full time Working part-time Unemployed Retired Other Missing Income < 1000 €
57.2 (12.7)
Females (n=5106) n (%) 56.2 (12.2)
Total sample (n=9721) n (%) 56.7 (12.4)
255 1205 1021 1170 964
(5.5) (26.1) (22.1) (25.4) (20.9)
257 1439 1230 1294 886
(5.0) (28.2) (24.1) (25.3) (17.4)
512 2644 2251 2464 1850
(5.3) (27.2) (23.2) (25.3) (19.0)
2962 101 907 525 113 7
(64.2) (2.2) (19.7) (11.4) (2.4) (0.2)
2854 132 830 813 468 9
(55.9) (2.6) (16.3) (15.9) (9.2) (0.2)
5816 233 1737 1338 581 16
(59.8) (2.4) (17.9) (13.7) (6.0) (0.2)
361 2488 1694 72
(7.8) (53.9) (36.7) (1.6)
396 3026 1618 66
(7.8) (59.3) (31.7) (1.3)
757 5514 3312 138
(7.8) (56.7) (34.1) (1.4)
2308 164 301 1734 68 40
(50.0) (3.6) (6.5) (37.6) (1.5) (0.9)
1975 751 307 1860 152 61
(38.7) (14.7) (6.0) (36.4) (3.0) (1.2)
4283 915 608 3594 220 101
(44.1) (9.4) (6.3) (37.0) (2.3) (1.0)
948
19.9
1896
36.2
2844
28.4
16 1000 - < 2000 € ≥ 2000 € Missing Socioeconomic level Low Medium High Missing Smoking Current nonsmoker Current smoker Missing Alcohol consumption < 20 g/day ≥ 20 g/day Missing
2337 1236 245
49.0 25.9 5.1
2297 784 257
43.9 15.0 4.9
4634 2020 502
46.3 20.2 5.0
889 2683 1031 12
(19.3) (58.1) (22.3) (0.3)
1047 3131 911 17
(20.5) (61.3) (17.8) (0.3)
1936 5814 1942 29
(19.9) (59.8) (20.0) (0.3)
3462 1072 81
(75.0) (23.2) (1.8)
3936 1007 163
(77.1) (19.7) (3.2)
7398 2079 244
(76.1) (21.4) (2.5)
2860 1439 316
(62.0) (31.2) 6.8)
4411 351 344
(86.4) (6.9) (6.7)
7271 1790 660
(74.8) (18.4) (6.8)
17 Table 2. Cumulative percentages of the GAD-7 and GAD-2 scores Score Males Females Total GAD-7 0 22.4 15.0 18.5 1 38,7 26.0 32.1 2 53.9 39.1 46.1 3 66.7 51.1 58.5 4 75.6 62.4 68.6 5 82.4 71.7 76.8 6 88.1 79.5 83.6 7 92.3 85.9 89.0 8 94.5 89.6 91.9 9 95.8 92.6 94.1 10 97.0 94.3 95.6 11 97.7 95.8 96.7 12 98.3 97.1 97.6 13 98.7 97.8 98.2 14 99.1 98.5 98.8 15 99.3 98.9 99.1 16 99.4 99.2 99.3 17 99.6 99.4 99.5 18 99.7 99.7 99.7 19 99.8 99.8 99.8 20 99.9 99.9 99.9 21 100.0 100.0 100.0 GAD-2 0 57.7 40.8 48.9 1 81.1 68.1 74.3 2 95.0 90.5 92.7 3 97.6 95.3 96.4 4 99.0 97.8 98.3 5 99.6 99.1 99.3 6 100.0 100.0 100.0
18 Table 3. GAD-7 component and global mean scores, sex differences, and item-total correlations 1. Feeling nervous 2. Not able to stop worrying 3. Worry about different things 4. Trouble relaxing 5. Being restless 6. Easily annoyed or irritable 7. Feeling afraid
Males M SD 0.41 0.61 0.30 0.56 0.49 0.65 0.57 0.68 0.39 0.64 0.61 0.63 0.24 0.52
Females M SD 0.64 0.71 0.44 0.66 0.65 0.70 0.81 0.78 0.50 0.72 0.65 0.64 0.36 0.61
Total M SD 0.53 0.68 0.37 0.62 0.57 0.68 0.70 0.74 0.45 0.69 0.63 0.63 0.31 0.57
GAD-2 sum score GAD-7 sum score
0.71 1.04 3.01 3.12
1.09 1.22 4.07 3.53
0.91 1.15 3.57 3.38
d(sex) 0.35 0.23 0.24 0.33 0.16 0.06 0.21
rit 0.67 0.69 0.68 0.66 0.52 0.52 0.60
0.33 α= 0.72 0.32 α= 0.85
19 Table 4. Fit indices for multigroup CFA Model Total model Gender Model 1: same item-factor assign. Model 2: Model 1 + equiv. factor loadings Model 3: Model 1 + equiv. factor loadings + equiv. intercepts Age groups Model 1: same item-factor assign Model 2: Model 1 + equiv. factor loadings Model 3: Model 1 + equiv. factor loadings + equiv. intercepts
χ² 517.5
df 14
χ²/df 37.0
CFI 0.970
TLI 0.954
RMSEA 0.085
193.9 208.0
28 35
6.93 5.94
0.954 0.952
0.931 0.942
0.064 0.059
217.9
42
5.19
0.951
0.951
0.054
1032.6 1166.7
70 98
14.7 11.9
0.960 0.956
0.940 0.952
0.039 0.034
1528.9
126
12.1
0.942
0.951
0.035
20 Table 5. Correlations with other scales PCS MCS Fatigue Opti- Pessi- Physical Sleep Daytime Life Social mism mism com- prob- Sleepi- satis- support plaints lems ness faction SF-8 SF-8 MFI LOT-R LOT-R PHQ-15 PSQI ESS SWLS ESSI 1. Feeling nervous 2. Not able to stop worrying 3. Worry about different things 4. Trouble relaxing 5. Being restless 6. Easily annoyed or irritable 7. Feeling afraid
-.18 -.21
-.59 -.58
.42 .44
-.22 -.27
.19 .26
.44 .40
.35 .33
.13 .14
-.33 -.37
-.20 -.23
-.20
-.55
.39
-.24
.26
.40
.34
.13
-.36
-.21
-.22 -.19 -.14
-.53 -.35 -.40
.42 .29 .31
-.22 -.16 -.17
.20 .21 .19
.45 .34 .33
.42 .29 .24
.15 .12 .18
-.34 -.22 -.23
-.22 -.17 -.17
-.21
-.50
.37
-.25
.28
.38
.30
.12
-.28
-.20
GAD-2 sum score GAD-7 sum score
-.22 -.26
-.66 -.68
.48 .52
-.27 -.30
.25 .31
.47 .54
.38 .45
.15 .19
-.39 -.42
-.24 -.27
21 Table 6. GAD-7 mean scores, broken down by sociodemographic and behavioral variables Males (n=4615) M SD Marital status (F=6.6, p<0.001) Married, living together Married, living separately Never married Divorced Widowed Education (F=22.2; p<0.01) 10 years 10-11 years 12 years Occupation (F=38.9, p<0.001) Working full time Working part-time Unemployed Retired Other Income (F=34.9, p<0.001) < 1000 € 1000 - < 2000 € ≥ 2000 € Socioeconomic level (F=34.9, p<0.001) Low Medium High Tobacco (F=13.0, p<0.001) Current nonsmoker Current smoker Alcohol (F=14.6, p<0.001) < 20 g/day ≥ 20 g/day
Females (n=5106) M SD
Total (n=9721) M SD
2.82 4.00 3.35 3.35 2.86
2.90 3.79 3.39 3.60 2.79
4.01 4.11 4.02 4.48 3.82
3.41 3.92 3.47 3.87 3.58
3.40 4.06 3.67 4.03 3.63
3.22 3.86 3.44 3.80 3.45
3.23 3.06 2.85
3.32 3.15 2.92
4.24 4.19 3.77
3.62 3.60 3.32
3.76 3.68 3.30
3.52 3.45 3.16
2.92 3.12 4.23 2.91 3.22
2.97 2.94 4.19 3.05 3.62
3.90 4.14 5.36 3.97 4.07
3.42 3.47 4.29 3.46 3.31
3.37 3.96 4.80 3.46 3.81
3.22 3.40 4.27 3.31 3.42
3.65 2.88 2.83
3.75 3.00 2.85
4.46 3.93 3.59
3.74 3.41 3.29
4.20 3.40 3.13
3.76 3.25 3.05
4.14 3.08 2.75
4.27 3.13 2.85
5.24 4.17 3.66
4.28 3.57 3.21
4.71 3.70 3.18
4.31 3.43 3.06
2.96 3.16
3.05 3.33
3.89 4.63
3.40 3.89
3.46 3.87
3.27 3.68
2.91 3.11
3.10 3.04
3.98 4.73
3.49 3.68
3.56 3.43
3.38 3.24
Highlights
- The study confirmed good psychometric properties of the GAD-7.
- The psychometric quality of the GAD-7 is superior to that of the ultra-short GAD-2.
- Women are more anxious than men, but there is no linear age trend in anxiety.
- Anxiety is associated with alcohol consumption and cigarette smoking, especially in women.
22