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anxiety in the general population
Journal of Affective Disorders 128 (2011) 106–111
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Journal of Affective Disorders j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j a d
Research report
Base rates for depersonalization according to the 2-item version of the Cambridge Depersonalization Scale (CDS-2) and its associations with depression/anxiety in the general population Matthias Michal a,⁎,1, Heide Glaesmer b,1, Rüdiger Zwerenz a, Achim Knebel a, Jörg Wiltink a, Elmar Brähler b, Manfred E. Beutel a a b
Department of Psychosomatic Medicine and Psychotherapy, University Medical Center of the Johannes Gutenberg University Mainz, Germany Department of Medical Psychology and Sociology, University of Leipzig, Germany
a r t i c l e
i n f o
Article history: Received 26 February 2010 Received in revised form 25 June 2010 Accepted 25 June 2010 Available online 31 July 2010
Keywords: Depersonalization Depression Anxiety Screening
a b s t r a c t Background: Recently, the two item version of the Cambridge Depersonalization Scale (CDS-2) has been validated in a clinical sample and has demonstrated that it is a useful tool for the detection of clinically significant depersonalization (DP). In order to provide a framework for the interpretation of the CDS-2 scores the aim of this study was to achieve normative data of a representative sample of the German population and to evaluate the associations with depression, anxiety and sociodemographic characteristics. Methods: A nationally representative face-to-face household survey was conducted during the mid of 2009 in Germany. The sample comprised N = 2512 participants. The survey questionnaire consisted of the CDS-2, the Hospital Anxiety and Depression Scale, and demographic characteristics. Results: Case level of DP was found for 3.4% of the participants without significant sex and age differences. Although DP was strongly associated with depression and anxiety, principal component analysis clearly supported the distinctiveness of the psychopathological syndromes of depression, anxiety and DP. Limitations: A criterion standard diagnostic interview for DP, anxiety and depression was not included. Conclusions: The results provide a framework for the interpretation of the CDS-2 scores and support the view that DP is a common and distinct psychopathological syndrome. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Depersonalization (DP) is defined as the subjective experience of detachment from one's sense of self, often accompanied by derealization — a threatening sense of unreality in the environment. Phenomena of DP occur on a continuum spanning from transient episodes to a significant symptomcomplex in the context of other psychiatric illnesses or as a primary mental disorder (Lambert et al., 2001; Sierra, 2009; ⁎ Corresponding author. E-mail address: [email protected] (M. Michal). 1 These authors contributed equally. 0165-0327/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2010.06.033
Simeon and Abugel, 2006). Review of the literature suggests that DP represents a clinical index of disease severity and poorer treatment response (Mula et al., 2007). According to epidemiological studies transient symptoms of DP are common in the general population with a lifetime prevalence rate between 26% and 74%. For clinically significant DP prevalence rates of 1–2% have been reported (Hunter et al., 2004; Michal et al., 2009). Despite the high prevalence and clinical relevance of DP as a symptom-complex and as a mental disorder, DP is strongly underdiagnosed (Medford et al., 2005; Simeon, 2004). A recent analysis of the 1-year-prevalence of all medical diagnoses of 1.567 million insured persons of a statutory health insurance fund in Germany revealed a 1-year-prevalence for
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the diagnosis of depersonalization disorder of only 0.007% (Michal et al., 2010a). This demonstrates a dramatic neglect of DP in clinical routine. Therefore, efforts should be undertaken to increase diagnostic awareness for DP. For this purpose we developed an ultra brief 2-item scale for DP, i.e. the two item version of the Cambridge Depersonalization Scale (CDS-2, Michal et al., 2010c). The items of the CDS-2 were extracted from the Cambridge Depersonalization Scale (CDS, Sierra and Berrios, 2000), which is currently the most detailed and valid measure describing and quantifying depersonalization and derealization experiences. In order to provide a framework for the interpretation of the CDS-2 scores the aim of this study was to achieve normative data of a representative sample of the German population and to evaluate the associations with depression, anxiety and sociodemographics. 2. Methods 2.1. Subjects The survey was conducted in the mid of the year 2009 as part of a broader survey on different aspects of mental distress, internet usage/addiction, emotion regulation and bodily complaints. A representative sample of the general population of Germany was selected with the assistance of a demography consulting company (USUMA, Berlin). A total of 258 sample points were used. Inclusion criteria were age above 13 years and German as a native language. A first attempt was made for N = 4630 addresses following a random-route procedure. From the N = 4630 selected addresses, N = 4572 were valid. All participants were visited by an interviewer, informed about the investigation and provided written informed consent. A total of N = 2524 persons agreed to participate (response rate = 55.2%) and N = 2512 interviews and questionnaires were suitable for evaluation. Of those N = 1401 were female (55.8%) and N = 1111 (44.2%) male. The mean age of the participants was 49.4 ± 18.2 years (range age 14–94), N = 1403 (55.9%) lived within a partnership. With respect to status of employment, N = 1200 (47.8%) were employed, N = 195 (7.8%) were out of engagement, and N = 1395 (55.5%) were unemployed. With respect to age, sex and education the sociodemographic characteristics of the study sample closely match those of the total population in Germany. 2.2. Assessment The Cambridge Depersonalization Scale (CDS, (Sierra and Berrios, 2000)) captures the complex phenomenology of the depersonalization–derealization syndrome with 29 items and has become increasingly used in depersonalization research (Michal and Beutel, 2009; Michal et al., 2004; Sierra and Berrios, 2000; Simeon et al., 2008; Stein and Simeon, 2009). For the construction of the ultra brief version of the CDS two items were selected discriminating best between patients with clinically significant DP and patients without clinically significant DP. These two items were assembled to the 2 item version of the CDS. The response format of the CDS-2 was adopted from the Patient Health Questionnaire (“Over the last 2 weeks, how often have you been bothered
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by any of the following problems?/Not at all = 0/Several days = 1/More than half the days = 2/Nearly every day = 3”; Löwe et al., 2005; Michal et al., 2010c). The CDS-2 was originally tested in a sample of 38 patients with clinical significant DP-DR and 49 patients without or only mild DPDR. Scores were compared against clinical diagnoses based on the Depersonalization Severity Scale as the gold standard (DSS, (Simeon et al., 2001)). The CDS-2 showed high reliability (Cronbach's alpha = 0.92) and was able to differentiate patients with clinically significant DP well from other groups (cut-off of CDS-2 ≥ 3, sensitivity = 78.9%, and specificity = 85.7%). The CDS-2 sum score (range 0–6) correlated strongly (r = 0.77) with depersonalization severity according to the DSS (Michal et al., 2010c). For the assessment of anxiety and depression the German version of the Hospital Anxiety and Depression Scale (HADS) (Herrmann et al., 1991; Zigmond and Snaith, 1983) was applied. The HADS comprises the anxiety subscale (HADS-A) and a depression subscale (HADS-D) both containing seven intermingled items. The scale is widely used in several countries (Bjelland et al., 2002; Herrmann, 1997). For the detection of depressive and anxiety disorders a cut-off point of ≥8 for the corresponding subscales yielded the optimal balance between sensitivity and specificity (Bjelland et al., 2002). Therefore, we used HADS-D ≥ 8 for the definition of caseness of depression and HADS-A ≥ 8 for the identification of clinically significant anxiety. 2.3. Statistical analysis The unweighted data were analyzed descriptively. Differences of distribution and means were analyzed by Chi2-test respectively the Kruskal–Wallis test. Associations between variables were calculated by Pearson correlations, logistic and linear regression analysis. A principal component analysis with varimax and promax rotation was performed on the items of the CDS-2 and HADS to evaluate the distinctiveness of the scales. Results of the best model were demonstrated. All statistics have been calculated with SPSS Statistics 17.0. 3. Results 3.1. Base rates for the items of the CDS-2 Base rates of the items of the CDS-2 are shown in Table 1. Item 1 was endorsed by 19.5% and item 2 by 16.0% of the participants. Both items were strongly correlated (r = 0.73, p b 0.001), and the internal consistency was satisfactory with Cronbach's alpha = 0.84. 3.2. Distribution of the CDS-2 scores in the sample The base rates of the CDS-2 scores stratified by decades of age are shown in Table 2. A proportion of 21.8% (N = 562) endorsed at least one item of the CDS-2 and 3.4% (N = 85) scored in the range of clinically significant DP. The mean score of the CDS-2 was 0.41 ± 0.89 (mean ± standard deviation). In order to test for differences in the age distribution of the CDS scores, we calculated the Kruskal–Wallis test with decades of age as the group variable and the sum scores of the
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0.64–1.46, p = 0.88) or with clinically significant DP (OR 1.23, 95%CI 0.62–2.43, p = 0.55).
Table 1 Base rates for the two items of the CDS-2. 0a
1
2
3
≥1
CDS-2 item 1: My surroundings feel 80.6% 16.9% 2.2% 0.4% 19.5% detached or unreal, as if there was a veil between me and the outside world. CDS-2 item 2: Out of the blue, I feel 84.0% 13.5% 2.2% 0.3% 16.0% strange, as if I were not real or as if I were cut off from the world. a Response format: Over the last 2 weeks, how often have you been bothered by any of the following problems? Not at all = 0/Several days = 1/More than half the days = 2/Nearly every day = 3.
CDS-2 as the dependent variable. No differences were found (Chi2 = 8576, df = 6, p = 0.199). Accordingly no significant correlation between age (in years) and the CDS-2 score emerged (r = 0.016, p = 0.410).
3.3. Sociodemographic correlates As shown in Table 3, persons with clinically significant DP tended to be slightly less educated, to have less household income, to be more often out of engagement, and to be more often unmarried and living without a partner. Differences for sex and age were not found. However, living without a partner, being out of engagement and lower education were no longer significantly associated with clinically significant DP after adjustment for caseness of anxiety and depression, age and sex: living in partnership was negatively associated with caseness of depression OR 0.38 (95%CI 0.30–0.48, p b 0.0001), positively with anxiety OR 1.47 (95%CI 1.15–1.85, p b 0.0001), age OR 1.02 (95%CI 1.014– 1.024, p b 0.0001), negatively with female sex OR 0.74 (95%CI 0.63–0.87, p b 0.0001), and not with clinically significant DP (OR 0.78, 95%CI 0.48–1.27, p = 0.33). Higher education (school versus university) was inversely associated with caseness of depression OR 0.51 (95%CI 0.35–0.74, p b 0.0001), positively with anxiety OR 1.51 (95%CI 1.08–2.12, p = 0.015), lower age OR 0.98 (95%CI 0.98–0.99, p b 0.0001), female sex OR 0.61 (95%CI 0.49–0.78, p b 0.0001), but not with clinically significant DP (OR 0.49, 95%CI 0.19–1.27, p = 0.14). Being out of engagement was associated with caseness of depression OR 2.77 (95%CI 1.85–4.13, p b 0.0001), lower age OR 0.96 (95%CI 0.96–0.97, p b 0.0001), but neither with sex (OR 0.96, 95%CI 0.71–1.30, p = 0.80), nor with anxiety (OR 0.96, 95%CI
3.4. Overlap and distinctiveness with anxiety and depression With respect to HADS case definition, 24.4% (N = 603) of the participants scored in the range of clinically significant depression (HADS-D ≥ 8), 22.1% (N = 548) were in the range of clinically significant anxiety (HADS-A ≥ 8), 14.7% (N = 362) fulfilled both criteria, and 31.7% (N = 779) met at least one criterion (i.e. HADS-A or HADS-D case level). In the total sample the mean scores for HADS-D were 4.64 ± 3.99 and for HADS-A 4.66 ± 3.67. Both conditions were positively correlated with age (HADS-A r = 0.07, p = 0.001; HADS-D r = 0.24, p b 0.001). With respect to sex distribution for depression no significant difference was found (OR 0.85, 95%CI 0.71–1.02, p = 0.091), however anxiety was more often in females (OR 1.23, 95%CI 1.02–1.50, p = 0.032). Depersonalization severity according to the CDS-2 scores correlated strongly with the HADS-depression subscale (r = 0.51, p b 0.001) as well as with the anxiety subscale (r = 0.52, p b 0.001), but the correlation between the two HADS subscales was higher (r = 0.69, p b 0.001). In order to examine differential associations of anxiety and depression with depersonalization severity we performed a stepwise linear regression with the CDS-2 score as the dependent variable and HADS-A and HADS-D as the independent variables. Both variables explained 32.1% of the variance of depersonalization severity (F(df = 2, 2452) = 580.299, p b 0.001), HADS-A 27.3% (β = 0.320, p b 0.001) and HADS-D additionally 4.8% (β = 0.299, p b 0.001). Persons with clinically significant DP reached case level of depression in 90.1% and case level of anxiety in 76.8%. Only N = 3 persons with clinically significant DP reached neither case level of anxiety nor depression. These persons were two men (age 65 and 32 years) and one woman (age 17 years), with a mean score for HADS-A of 5.0 ± 3.5 and for HADS-D of 6.3 ± 1.2. This strong co-occurrence of DP with anxiety and depression is further illustrated in Fig. 1, showing that with increasing depersonalization severity, subjects also score increasingly in the range of clinically significant depression, anxiety or both conditions (depression and anxiety). In order to consider covariates, we calculated a logistic regression analysis with CDS ≥ 3 as the dependent variable, and anxiety (HADS-A ≥ 8), depression (HADS-D ≥ 8) as the predictors adjusted for age (in years) and sex. A strong association of clinically significant DP was found with depression OR 17.72
Table 2 Base rates of the CDS-2 scores in the sample stratified for decades of age. CDS-2 score
0 1 2 3 4 5 6 ≥3
Age groups 14–24 years N = 258
25–34 years N = 352
35–44 years N = 423
45–54 years N = 443
55–64 years N = 403
65–74 years N = 404
N75 years N = 221
74.8% 9.7% 11.6% 1.9% 1.6% 0.4% 0.0% 3.9%
81.0% 10.2% 7.4% .9% .6% 0.0% 0.0% 1.4%
77.5% 10.4% 8.3% 1.9% .9% 0.5% 0.5% 3.8%
75.8% 9.5% 11.1% 2.0% 1.1% 0.0% 0.5% 3.6%
76.9% 7.9% 11.2% 2.7% 1.0% 0.2% 0.0% 4.0%
80.4% 7.7% 8.9% 1.5% 1.0% 0.2% 0.2% 3.0%
74.7% 9.5% 11.3% 1.8% 1.8% 0.9% 0.0% 4.5%
Total sample (N = 2504)
77.6% 9.2% 9.8% 1.8% 1.1% 0.3% 0.2% 3.4%
(N = 1942) (N = 231) (N = 246) (N = 46) (N = 27) (N = 7) (N = 5) (N = 85)
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Table 3 Sociodemographic characteristics of the sample stratified by clinically significant DP (CDS-2 ≥ 3).
Male, % Age (years) (mean ± standard deviation) Education No university degree versus university degree Marital status Married Married, living separate Unmarried Divorced Widowed Partner (yes = 1) Status of employment Out of engagement versus employed Household income (€ per month) b750 750–b1250 1250–b 2000 N2000
CDS-2 b 3 N = 2418
CDS-2 ≥ 3 N = 85
Test (Chi2 or OR with 95%CI)
44.2% 49 ± 18
44.7% 51 ± 18
OR 0.99 (0.98–1.01), n.s. OR 1.01 (0.99–1.02), n.s.
85.7% vs. 14.3%
94.1% vs. 5.9%
OR 0.38 (0.15–0.0.93), p = 0.025 Chi2 = 9.51, df = 4, p = 0.050
49.8 1.0% 25.9% 11.4% 12.0% 56.3%
35.3% 1.2% 27.1% 17.7% 18.8% 41.2%
13.4% vs. 86.6%
26.0% vs. 74.0%
5.4% 18.9% 34.3% 41.5%
10.8% 27.7% 30.1% 31.3%
(95%CI 7.86–39.95, p b 0.001) and anxiety OR 3.27 (95%CI 1.82–5.86, p b 0.001), but not with age (OR 0.99, 95%CI 0.98– 101) or sex (OR 1.09, 95%CI 0.68–1.76). In order to determine the overlap or distinctiveness of DP with depression and anxiety we performed a principal component analysis (PCA) with varimax rotation and Kaiser normalization on the items of the CDS-2 and the HADS together. Factors were retained in the model based on inspection of the screeplot and eigenvalues N1. Three factors were identified, explaining 57% of the variance. The depersonalization factor (F3) contained the two items of the CDS-2 and one item of the HADS-depression subscale (HADS item 10: I have lost interest in my appearance), which loaded also only marginally less on the depression factor (F1). With the exception of the items 7, 8 and 10 the factor structure of the HADS could be replicated (see Table 4). Additionally the principal component analysis was repeated with promax
OR 0.44 (95%CI 0.23–0.85), p = 0.020 Chi2 = 10.03, df = 3, p = 0.018
rotation. The factor loadings obtained with promax rotation were very similar to the results of the varimax rotation and clearly supported the separateness of the three factor solution. The factor correlation matrix showed strong correlations between the depersonalization factor with the depression (0.57) and anxiety factor (0.57). However, a substantial amount of unique variance for each factor remained. 4. Discussion This study provides further evidence that DP is common in the general population of Germany. With respect to previous studies we found the surprisingly high prevalence for clinically significant DP of 3.4%, exceeding previously Table 4 Principal component analysis with varimax rotation on the items of the CDS2 and the HADS: factor loadings. Scale and items
Fig. 1. Prevalences of depression, anxiety or the composite of both conditions according to HADS stratified by depersonalization severity according to the CDS-2 scores.
OR 0.54 (0.35–0.84), p b 0.006
F1
CDS-2 1 0.207 2 0.186 Anxiety subscale of the HADS 1 0.167 3 0.231 5 0.335 7 0.635 9 0.341 11 − 0.01 13 0.276 Depression subscale of the HADS 2 0.767 4 0.786 6 0.667 8 0.387 10 0.369 12 0.749 14 0.633 Eigenvalue 4 Explained variance 24% Bold: factor loadings N0.400.
F2
F3
0.219 0.162
0.847 0.870
0.712 0.701 0.668 0.349 0.477 0.584 0.603
0.059 0.239 0.235 0.181 0.255 0.007 0.384
0.176 0.174 0.253 0.520 0.181 0.182 0.086 3 19%
0.149 0.161 0.256 0.244 0.465 0.165 0.122 2 14%
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reported rates of 0.8–2% (Michal et al., 2009, Michal et al., 2010b). This high morbidity of the sample was also found for caseness of depression (24.4%) and anxiety (22.1%). Therefore we do not interpret the high prevalence of clinically significant DP as an overinclusive screening failure of the CDS-2 but as a special characteristic of the sample. For all three conditions the prevalences are approximately twice to thrice as high as expected according to epidemiological studies. For example, Michal et al. (2009) found in a community survey from the year 2006 that 1.9% scored in the range of clinically significant DP, 8.6% were in the range of anxiety disorders and 4.7% in the case level of depression. On the other hand the mean scores of the HADS subscales (HADS-D = 4.64 ± 3.99; HADS-A = 4.66 ± 3.67) are very similar to a previous community survey in the German general population from 1998 (HADS-D 4.6 ± 3.8 for men, HADS-D 4.7 ± 3.9 for women; HADS-A 4.4 ± 3.1 for men, HADS-A 5.0 ± 3.4) supporting the representativeness of the sample (Hinz and Schwarz, 2001). With regard to the sociodemographics characteristics we found no differences in the sex distribution for clinically significant DP. This is in line with the majority of results based on clinical samples (Simeon, 2004) or epidemiological surveys (Michal et al., 2009). Interestingly clinically significant DP was similar prevalent over the life span, although according to the literature depersonalization disorder has an early age of onset around 16 to 23 years (Baker et al., 2003, Michal and Beutel, 2009, Sierra, 2009, Simeon, 2004, Medford et al., 2005). Moreover this result is not consistent with the finding of a survey in a southern rural US population, which reported a significantly decreasing prevalence of depersonalization and derealization with increasing age (OR = 0.73, 95%CI = 0.65–0.81, Aderibigbe et al., 2001). With respect to the overlap between DP and anxiety or depression our study confirmed the high co-occurrence. Almost all persons with clinically significant DP were also in the range of clinically significant depression or anxiety. These rates are comparable high to those found in clinical samples of DP disorder, which were 41% to 64% for current anxiety disorders and 33% to 67% for current depressive disorders (Baker et al., 2003; Michal et al., 2005; Simeon et al., 2003). However, although DP co-occurs usually with depression and anxiety, the shared variance of depersonalization severity with anxiety and depression was only 32.1%. Interestingly, HADS-A explained 27.3% and HADS-D only 4.8% of the variance. It is important to note that the depressive subscale of the HADS measures mainly anhedonia (Kendel et al., 2010). Therefore the low proportion of the shared variance seems even more intriguing, because depressive anhedonia is often confused with loss of feelings respectively affective depersonalization (Mula et al., 2010). Thus the present finding is in line with Mula et al. (2010), who could clearly distinguish anhedonia from affective depersonalization in a clinical sample of patients with mood and anxiety disorders. Furthermore, the results of the principal component analysis supported the clear distinctiveness of the three psychopathological syndromes and argue against the common misunderstanding of DP as just being a negligible variant of anxiety and depression. Limitations of our study include the lack of standard diagnostic instruments for anxiety, depression and deper-
sonalization, the low response rate of 55.2% and concerns about the representativeness of the sample in terms of the unexpected high prevalence of anxiety, depression and DP. Further studies are warranted to reappraise these findings. In conclusion, the present findings support the validity and high internal consistency of the CDS-2, they provide normative data and base rates helpful for the interpretation of the CDS-2 scores and support the view that DP, despite its high co-occurrence with anxiety and depression, is a clear distinct psychopathological syndrome. In order to increase diagnostic awareness of DP the CDS-2 could be easily included to an ultra brief screening scale for depression and anxiety like the Patient Health Questionnaire-4 (Löwe et al., 2010). Role of funding source Nothing declared. Conflict of interest No conflict declared.
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Sierra, M., 2009. Depersonalization: A New Look at a Neglected Syndrome. Cambridge University Press. Sierra, M., Berrios, G.E., 2000. The Cambridge Depersonalization Scale: a new instrument for the measurement of depersonalization. Psychiatry Res. 93, 153–164. Simeon, D., 2004. Depersonalisation disorder: a contemporary overview. CNS Drugs 18, 343–354. Simeon, D., Abugel, J., 2006. Feeling Unreal: Depersonalization Disorder and the Loss of the Self. Oxford University Press. Simeon, D., Guralnik, O., Schmeidler, J., 2001. Development of a depersonalization severity scale. J. Trauma. Stress 14, 341–349. Simeon, D., Knutelska, M., Nelson, D., Guralnik, O., 2003. Feeling unreal: a depersonalization disorder update of 117 cases. J. Clin. Psychiatry 64, 990–997. Simeon, D., Kozin, D.S., Segal, K., Lerch, B., Dujour, R., Giesbrecht, T., 2008. De-constructing depersonalization: further evidence for symptom clusters. Psychiatry Res. 157, 303–306. Stein, D.J., Simeon, D., 2009. Cognitive–affective neuroscience of depersonalization. CNS Spectr. 14, 467–471. Zigmond, A.S., Snaith, R.P., 1983. The hospital anxiety and depression scale. Acta Psychiatr. Scand. 67, 361–370.
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Journal of Affective Disorders j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / j a d
Research report
Base rates for depersonalization according to the 2-item version of the Cambridge Depersonalization Scale (CDS-2) and its associations with depression/anxiety in the general population Matthias Michal a,⁎,1, Heide Glaesmer b,1, Rüdiger Zwerenz a, Achim Knebel a, Jörg Wiltink a, Elmar Brähler b, Manfred E. Beutel a a b
Department of Psychosomatic Medicine and Psychotherapy, University Medical Center of the Johannes Gutenberg University Mainz, Germany Department of Medical Psychology and Sociology, University of Leipzig, Germany
a r t i c l e
i n f o
Article history: Received 26 February 2010 Received in revised form 25 June 2010 Accepted 25 June 2010 Available online 31 July 2010
Keywords: Depersonalization Depression Anxiety Screening
a b s t r a c t Background: Recently, the two item version of the Cambridge Depersonalization Scale (CDS-2) has been validated in a clinical sample and has demonstrated that it is a useful tool for the detection of clinically significant depersonalization (DP). In order to provide a framework for the interpretation of the CDS-2 scores the aim of this study was to achieve normative data of a representative sample of the German population and to evaluate the associations with depression, anxiety and sociodemographic characteristics. Methods: A nationally representative face-to-face household survey was conducted during the mid of 2009 in Germany. The sample comprised N = 2512 participants. The survey questionnaire consisted of the CDS-2, the Hospital Anxiety and Depression Scale, and demographic characteristics. Results: Case level of DP was found for 3.4% of the participants without significant sex and age differences. Although DP was strongly associated with depression and anxiety, principal component analysis clearly supported the distinctiveness of the psychopathological syndromes of depression, anxiety and DP. Limitations: A criterion standard diagnostic interview for DP, anxiety and depression was not included. Conclusions: The results provide a framework for the interpretation of the CDS-2 scores and support the view that DP is a common and distinct psychopathological syndrome. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Depersonalization (DP) is defined as the subjective experience of detachment from one's sense of self, often accompanied by derealization — a threatening sense of unreality in the environment. Phenomena of DP occur on a continuum spanning from transient episodes to a significant symptomcomplex in the context of other psychiatric illnesses or as a primary mental disorder (Lambert et al., 2001; Sierra, 2009; ⁎ Corresponding author. E-mail address: [email protected] (M. Michal). 1 These authors contributed equally. 0165-0327/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2010.06.033
Simeon and Abugel, 2006). Review of the literature suggests that DP represents a clinical index of disease severity and poorer treatment response (Mula et al., 2007). According to epidemiological studies transient symptoms of DP are common in the general population with a lifetime prevalence rate between 26% and 74%. For clinically significant DP prevalence rates of 1–2% have been reported (Hunter et al., 2004; Michal et al., 2009). Despite the high prevalence and clinical relevance of DP as a symptom-complex and as a mental disorder, DP is strongly underdiagnosed (Medford et al., 2005; Simeon, 2004). A recent analysis of the 1-year-prevalence of all medical diagnoses of 1.567 million insured persons of a statutory health insurance fund in Germany revealed a 1-year-prevalence for
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the diagnosis of depersonalization disorder of only 0.007% (Michal et al., 2010a). This demonstrates a dramatic neglect of DP in clinical routine. Therefore, efforts should be undertaken to increase diagnostic awareness for DP. For this purpose we developed an ultra brief 2-item scale for DP, i.e. the two item version of the Cambridge Depersonalization Scale (CDS-2, Michal et al., 2010c). The items of the CDS-2 were extracted from the Cambridge Depersonalization Scale (CDS, Sierra and Berrios, 2000), which is currently the most detailed and valid measure describing and quantifying depersonalization and derealization experiences. In order to provide a framework for the interpretation of the CDS-2 scores the aim of this study was to achieve normative data of a representative sample of the German population and to evaluate the associations with depression, anxiety and sociodemographics. 2. Methods 2.1. Subjects The survey was conducted in the mid of the year 2009 as part of a broader survey on different aspects of mental distress, internet usage/addiction, emotion regulation and bodily complaints. A representative sample of the general population of Germany was selected with the assistance of a demography consulting company (USUMA, Berlin). A total of 258 sample points were used. Inclusion criteria were age above 13 years and German as a native language. A first attempt was made for N = 4630 addresses following a random-route procedure. From the N = 4630 selected addresses, N = 4572 were valid. All participants were visited by an interviewer, informed about the investigation and provided written informed consent. A total of N = 2524 persons agreed to participate (response rate = 55.2%) and N = 2512 interviews and questionnaires were suitable for evaluation. Of those N = 1401 were female (55.8%) and N = 1111 (44.2%) male. The mean age of the participants was 49.4 ± 18.2 years (range age 14–94), N = 1403 (55.9%) lived within a partnership. With respect to status of employment, N = 1200 (47.8%) were employed, N = 195 (7.8%) were out of engagement, and N = 1395 (55.5%) were unemployed. With respect to age, sex and education the sociodemographic characteristics of the study sample closely match those of the total population in Germany. 2.2. Assessment The Cambridge Depersonalization Scale (CDS, (Sierra and Berrios, 2000)) captures the complex phenomenology of the depersonalization–derealization syndrome with 29 items and has become increasingly used in depersonalization research (Michal and Beutel, 2009; Michal et al., 2004; Sierra and Berrios, 2000; Simeon et al., 2008; Stein and Simeon, 2009). For the construction of the ultra brief version of the CDS two items were selected discriminating best between patients with clinically significant DP and patients without clinically significant DP. These two items were assembled to the 2 item version of the CDS. The response format of the CDS-2 was adopted from the Patient Health Questionnaire (“Over the last 2 weeks, how often have you been bothered
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by any of the following problems?/Not at all = 0/Several days = 1/More than half the days = 2/Nearly every day = 3”; Löwe et al., 2005; Michal et al., 2010c). The CDS-2 was originally tested in a sample of 38 patients with clinical significant DP-DR and 49 patients without or only mild DPDR. Scores were compared against clinical diagnoses based on the Depersonalization Severity Scale as the gold standard (DSS, (Simeon et al., 2001)). The CDS-2 showed high reliability (Cronbach's alpha = 0.92) and was able to differentiate patients with clinically significant DP well from other groups (cut-off of CDS-2 ≥ 3, sensitivity = 78.9%, and specificity = 85.7%). The CDS-2 sum score (range 0–6) correlated strongly (r = 0.77) with depersonalization severity according to the DSS (Michal et al., 2010c). For the assessment of anxiety and depression the German version of the Hospital Anxiety and Depression Scale (HADS) (Herrmann et al., 1991; Zigmond and Snaith, 1983) was applied. The HADS comprises the anxiety subscale (HADS-A) and a depression subscale (HADS-D) both containing seven intermingled items. The scale is widely used in several countries (Bjelland et al., 2002; Herrmann, 1997). For the detection of depressive and anxiety disorders a cut-off point of ≥8 for the corresponding subscales yielded the optimal balance between sensitivity and specificity (Bjelland et al., 2002). Therefore, we used HADS-D ≥ 8 for the definition of caseness of depression and HADS-A ≥ 8 for the identification of clinically significant anxiety. 2.3. Statistical analysis The unweighted data were analyzed descriptively. Differences of distribution and means were analyzed by Chi2-test respectively the Kruskal–Wallis test. Associations between variables were calculated by Pearson correlations, logistic and linear regression analysis. A principal component analysis with varimax and promax rotation was performed on the items of the CDS-2 and HADS to evaluate the distinctiveness of the scales. Results of the best model were demonstrated. All statistics have been calculated with SPSS Statistics 17.0. 3. Results 3.1. Base rates for the items of the CDS-2 Base rates of the items of the CDS-2 are shown in Table 1. Item 1 was endorsed by 19.5% and item 2 by 16.0% of the participants. Both items were strongly correlated (r = 0.73, p b 0.001), and the internal consistency was satisfactory with Cronbach's alpha = 0.84. 3.2. Distribution of the CDS-2 scores in the sample The base rates of the CDS-2 scores stratified by decades of age are shown in Table 2. A proportion of 21.8% (N = 562) endorsed at least one item of the CDS-2 and 3.4% (N = 85) scored in the range of clinically significant DP. The mean score of the CDS-2 was 0.41 ± 0.89 (mean ± standard deviation). In order to test for differences in the age distribution of the CDS scores, we calculated the Kruskal–Wallis test with decades of age as the group variable and the sum scores of the
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0.64–1.46, p = 0.88) or with clinically significant DP (OR 1.23, 95%CI 0.62–2.43, p = 0.55).
Table 1 Base rates for the two items of the CDS-2. 0a
1
2
3
≥1
CDS-2 item 1: My surroundings feel 80.6% 16.9% 2.2% 0.4% 19.5% detached or unreal, as if there was a veil between me and the outside world. CDS-2 item 2: Out of the blue, I feel 84.0% 13.5% 2.2% 0.3% 16.0% strange, as if I were not real or as if I were cut off from the world. a Response format: Over the last 2 weeks, how often have you been bothered by any of the following problems? Not at all = 0/Several days = 1/More than half the days = 2/Nearly every day = 3.
CDS-2 as the dependent variable. No differences were found (Chi2 = 8576, df = 6, p = 0.199). Accordingly no significant correlation between age (in years) and the CDS-2 score emerged (r = 0.016, p = 0.410).
3.3. Sociodemographic correlates As shown in Table 3, persons with clinically significant DP tended to be slightly less educated, to have less household income, to be more often out of engagement, and to be more often unmarried and living without a partner. Differences for sex and age were not found. However, living without a partner, being out of engagement and lower education were no longer significantly associated with clinically significant DP after adjustment for caseness of anxiety and depression, age and sex: living in partnership was negatively associated with caseness of depression OR 0.38 (95%CI 0.30–0.48, p b 0.0001), positively with anxiety OR 1.47 (95%CI 1.15–1.85, p b 0.0001), age OR 1.02 (95%CI 1.014– 1.024, p b 0.0001), negatively with female sex OR 0.74 (95%CI 0.63–0.87, p b 0.0001), and not with clinically significant DP (OR 0.78, 95%CI 0.48–1.27, p = 0.33). Higher education (school versus university) was inversely associated with caseness of depression OR 0.51 (95%CI 0.35–0.74, p b 0.0001), positively with anxiety OR 1.51 (95%CI 1.08–2.12, p = 0.015), lower age OR 0.98 (95%CI 0.98–0.99, p b 0.0001), female sex OR 0.61 (95%CI 0.49–0.78, p b 0.0001), but not with clinically significant DP (OR 0.49, 95%CI 0.19–1.27, p = 0.14). Being out of engagement was associated with caseness of depression OR 2.77 (95%CI 1.85–4.13, p b 0.0001), lower age OR 0.96 (95%CI 0.96–0.97, p b 0.0001), but neither with sex (OR 0.96, 95%CI 0.71–1.30, p = 0.80), nor with anxiety (OR 0.96, 95%CI
3.4. Overlap and distinctiveness with anxiety and depression With respect to HADS case definition, 24.4% (N = 603) of the participants scored in the range of clinically significant depression (HADS-D ≥ 8), 22.1% (N = 548) were in the range of clinically significant anxiety (HADS-A ≥ 8), 14.7% (N = 362) fulfilled both criteria, and 31.7% (N = 779) met at least one criterion (i.e. HADS-A or HADS-D case level). In the total sample the mean scores for HADS-D were 4.64 ± 3.99 and for HADS-A 4.66 ± 3.67. Both conditions were positively correlated with age (HADS-A r = 0.07, p = 0.001; HADS-D r = 0.24, p b 0.001). With respect to sex distribution for depression no significant difference was found (OR 0.85, 95%CI 0.71–1.02, p = 0.091), however anxiety was more often in females (OR 1.23, 95%CI 1.02–1.50, p = 0.032). Depersonalization severity according to the CDS-2 scores correlated strongly with the HADS-depression subscale (r = 0.51, p b 0.001) as well as with the anxiety subscale (r = 0.52, p b 0.001), but the correlation between the two HADS subscales was higher (r = 0.69, p b 0.001). In order to examine differential associations of anxiety and depression with depersonalization severity we performed a stepwise linear regression with the CDS-2 score as the dependent variable and HADS-A and HADS-D as the independent variables. Both variables explained 32.1% of the variance of depersonalization severity (F(df = 2, 2452) = 580.299, p b 0.001), HADS-A 27.3% (β = 0.320, p b 0.001) and HADS-D additionally 4.8% (β = 0.299, p b 0.001). Persons with clinically significant DP reached case level of depression in 90.1% and case level of anxiety in 76.8%. Only N = 3 persons with clinically significant DP reached neither case level of anxiety nor depression. These persons were two men (age 65 and 32 years) and one woman (age 17 years), with a mean score for HADS-A of 5.0 ± 3.5 and for HADS-D of 6.3 ± 1.2. This strong co-occurrence of DP with anxiety and depression is further illustrated in Fig. 1, showing that with increasing depersonalization severity, subjects also score increasingly in the range of clinically significant depression, anxiety or both conditions (depression and anxiety). In order to consider covariates, we calculated a logistic regression analysis with CDS ≥ 3 as the dependent variable, and anxiety (HADS-A ≥ 8), depression (HADS-D ≥ 8) as the predictors adjusted for age (in years) and sex. A strong association of clinically significant DP was found with depression OR 17.72
Table 2 Base rates of the CDS-2 scores in the sample stratified for decades of age. CDS-2 score
0 1 2 3 4 5 6 ≥3
Age groups 14–24 years N = 258
25–34 years N = 352
35–44 years N = 423
45–54 years N = 443
55–64 years N = 403
65–74 years N = 404
N75 years N = 221
74.8% 9.7% 11.6% 1.9% 1.6% 0.4% 0.0% 3.9%
81.0% 10.2% 7.4% .9% .6% 0.0% 0.0% 1.4%
77.5% 10.4% 8.3% 1.9% .9% 0.5% 0.5% 3.8%
75.8% 9.5% 11.1% 2.0% 1.1% 0.0% 0.5% 3.6%
76.9% 7.9% 11.2% 2.7% 1.0% 0.2% 0.0% 4.0%
80.4% 7.7% 8.9% 1.5% 1.0% 0.2% 0.2% 3.0%
74.7% 9.5% 11.3% 1.8% 1.8% 0.9% 0.0% 4.5%
Total sample (N = 2504)
77.6% 9.2% 9.8% 1.8% 1.1% 0.3% 0.2% 3.4%
(N = 1942) (N = 231) (N = 246) (N = 46) (N = 27) (N = 7) (N = 5) (N = 85)
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Table 3 Sociodemographic characteristics of the sample stratified by clinically significant DP (CDS-2 ≥ 3).
Male, % Age (years) (mean ± standard deviation) Education No university degree versus university degree Marital status Married Married, living separate Unmarried Divorced Widowed Partner (yes = 1) Status of employment Out of engagement versus employed Household income (€ per month) b750 750–b1250 1250–b 2000 N2000
CDS-2 b 3 N = 2418
CDS-2 ≥ 3 N = 85
Test (Chi2 or OR with 95%CI)
44.2% 49 ± 18
44.7% 51 ± 18
OR 0.99 (0.98–1.01), n.s. OR 1.01 (0.99–1.02), n.s.
85.7% vs. 14.3%
94.1% vs. 5.9%
OR 0.38 (0.15–0.0.93), p = 0.025 Chi2 = 9.51, df = 4, p = 0.050
49.8 1.0% 25.9% 11.4% 12.0% 56.3%
35.3% 1.2% 27.1% 17.7% 18.8% 41.2%
13.4% vs. 86.6%
26.0% vs. 74.0%
5.4% 18.9% 34.3% 41.5%
10.8% 27.7% 30.1% 31.3%
(95%CI 7.86–39.95, p b 0.001) and anxiety OR 3.27 (95%CI 1.82–5.86, p b 0.001), but not with age (OR 0.99, 95%CI 0.98– 101) or sex (OR 1.09, 95%CI 0.68–1.76). In order to determine the overlap or distinctiveness of DP with depression and anxiety we performed a principal component analysis (PCA) with varimax rotation and Kaiser normalization on the items of the CDS-2 and the HADS together. Factors were retained in the model based on inspection of the screeplot and eigenvalues N1. Three factors were identified, explaining 57% of the variance. The depersonalization factor (F3) contained the two items of the CDS-2 and one item of the HADS-depression subscale (HADS item 10: I have lost interest in my appearance), which loaded also only marginally less on the depression factor (F1). With the exception of the items 7, 8 and 10 the factor structure of the HADS could be replicated (see Table 4). Additionally the principal component analysis was repeated with promax
OR 0.44 (95%CI 0.23–0.85), p = 0.020 Chi2 = 10.03, df = 3, p = 0.018
rotation. The factor loadings obtained with promax rotation were very similar to the results of the varimax rotation and clearly supported the separateness of the three factor solution. The factor correlation matrix showed strong correlations between the depersonalization factor with the depression (0.57) and anxiety factor (0.57). However, a substantial amount of unique variance for each factor remained. 4. Discussion This study provides further evidence that DP is common in the general population of Germany. With respect to previous studies we found the surprisingly high prevalence for clinically significant DP of 3.4%, exceeding previously Table 4 Principal component analysis with varimax rotation on the items of the CDS2 and the HADS: factor loadings. Scale and items
Fig. 1. Prevalences of depression, anxiety or the composite of both conditions according to HADS stratified by depersonalization severity according to the CDS-2 scores.
OR 0.54 (0.35–0.84), p b 0.006
F1
CDS-2 1 0.207 2 0.186 Anxiety subscale of the HADS 1 0.167 3 0.231 5 0.335 7 0.635 9 0.341 11 − 0.01 13 0.276 Depression subscale of the HADS 2 0.767 4 0.786 6 0.667 8 0.387 10 0.369 12 0.749 14 0.633 Eigenvalue 4 Explained variance 24% Bold: factor loadings N0.400.
F2
F3
0.219 0.162
0.847 0.870
0.712 0.701 0.668 0.349 0.477 0.584 0.603
0.059 0.239 0.235 0.181 0.255 0.007 0.384
0.176 0.174 0.253 0.520 0.181 0.182 0.086 3 19%
0.149 0.161 0.256 0.244 0.465 0.165 0.122 2 14%
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reported rates of 0.8–2% (Michal et al., 2009, Michal et al., 2010b). This high morbidity of the sample was also found for caseness of depression (24.4%) and anxiety (22.1%). Therefore we do not interpret the high prevalence of clinically significant DP as an overinclusive screening failure of the CDS-2 but as a special characteristic of the sample. For all three conditions the prevalences are approximately twice to thrice as high as expected according to epidemiological studies. For example, Michal et al. (2009) found in a community survey from the year 2006 that 1.9% scored in the range of clinically significant DP, 8.6% were in the range of anxiety disorders and 4.7% in the case level of depression. On the other hand the mean scores of the HADS subscales (HADS-D = 4.64 ± 3.99; HADS-A = 4.66 ± 3.67) are very similar to a previous community survey in the German general population from 1998 (HADS-D 4.6 ± 3.8 for men, HADS-D 4.7 ± 3.9 for women; HADS-A 4.4 ± 3.1 for men, HADS-A 5.0 ± 3.4) supporting the representativeness of the sample (Hinz and Schwarz, 2001). With regard to the sociodemographics characteristics we found no differences in the sex distribution for clinically significant DP. This is in line with the majority of results based on clinical samples (Simeon, 2004) or epidemiological surveys (Michal et al., 2009). Interestingly clinically significant DP was similar prevalent over the life span, although according to the literature depersonalization disorder has an early age of onset around 16 to 23 years (Baker et al., 2003, Michal and Beutel, 2009, Sierra, 2009, Simeon, 2004, Medford et al., 2005). Moreover this result is not consistent with the finding of a survey in a southern rural US population, which reported a significantly decreasing prevalence of depersonalization and derealization with increasing age (OR = 0.73, 95%CI = 0.65–0.81, Aderibigbe et al., 2001). With respect to the overlap between DP and anxiety or depression our study confirmed the high co-occurrence. Almost all persons with clinically significant DP were also in the range of clinically significant depression or anxiety. These rates are comparable high to those found in clinical samples of DP disorder, which were 41% to 64% for current anxiety disorders and 33% to 67% for current depressive disorders (Baker et al., 2003; Michal et al., 2005; Simeon et al., 2003). However, although DP co-occurs usually with depression and anxiety, the shared variance of depersonalization severity with anxiety and depression was only 32.1%. Interestingly, HADS-A explained 27.3% and HADS-D only 4.8% of the variance. It is important to note that the depressive subscale of the HADS measures mainly anhedonia (Kendel et al., 2010). Therefore the low proportion of the shared variance seems even more intriguing, because depressive anhedonia is often confused with loss of feelings respectively affective depersonalization (Mula et al., 2010). Thus the present finding is in line with Mula et al. (2010), who could clearly distinguish anhedonia from affective depersonalization in a clinical sample of patients with mood and anxiety disorders. Furthermore, the results of the principal component analysis supported the clear distinctiveness of the three psychopathological syndromes and argue against the common misunderstanding of DP as just being a negligible variant of anxiety and depression. Limitations of our study include the lack of standard diagnostic instruments for anxiety, depression and deper-
sonalization, the low response rate of 55.2% and concerns about the representativeness of the sample in terms of the unexpected high prevalence of anxiety, depression and DP. Further studies are warranted to reappraise these findings. In conclusion, the present findings support the validity and high internal consistency of the CDS-2, they provide normative data and base rates helpful for the interpretation of the CDS-2 scores and support the view that DP, despite its high co-occurrence with anxiety and depression, is a clear distinct psychopathological syndrome. In order to increase diagnostic awareness of DP the CDS-2 could be easily included to an ultra brief screening scale for depression and anxiety like the Patient Health Questionnaire-4 (Löwe et al., 2010). Role of funding source Nothing declared. Conflict of interest No conflict declared.
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