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Affective disorders, anxiety disorders and psychological distress in non-drinkers
Journal of Affective Disorders 99 (2007) 165 – 172 www.elsevier.com/locate/jad
Research report
Affective disorders, anxiety disorders and psychological distress in non-drinkers Bryan Rodgers a,⁎, Ruth Parslow b , Louisa Degenhardt c a
National Centre for Epidemiology and Population Health, The Australian National University, Canberra ACT 0200, Australia b Orygen Research Centre, University of Melbourne, Australia c National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia Received 4 July 2005; received in revised form 5 September 2006; accepted 6 September 2006 Available online 12 October 2006
Abstract Background: Non-drinkers have elevated levels of psychological distress but a recent study reported no elevation in prevalence of diagnosed disorders. We aimed to determine the prevalence of affective and anxiety disorders (from the CIDI-A) in current abstainers and contrast results with findings for psychological distress (K10) in the same sample. Methods: Cross-sectional, representative household survey of adult Australians. Results: Non-/occasional drinkers had higher levels of psychological distress than light drinkers, and distress in heavy drinkers was even higher. Heavy drinkers also had the highest rates of most disorders. Non-/occasional drinkers showed significantly elevated prevalence only of dysthymia, agoraphobia and posttraumatic stress disorder compared with light drinkers. Limitations: Statistical power was limited for investigating low prevalence disorders. History of alcohol consumption was not collected. The CIDI-A and K10 have finite validity. Conclusions: This study confirmed J-shaped relationships between psychological distress and alcohol consumption. Although affective and anxiety disorders also showed non-linear relationships with alcohol consumption, non-/occasional drinkers are not at increased risk for all disorders compared to light drinkers. The pattern of symptomatology in non-/occasional drinkers may be of a different character to that in heavy drinkers, as well as being less severe. © 2006 Elsevier B.V. All rights reserved. Keywords: Depression; Anxiety; Alcohol drinking; Temperance; Comorbidity
1. Introduction Although many reports indicate a high prevalence of affective and anxiety disorders in people with alcohol use disorders (Regier et al., 1990; Dick et al., 1994; Grant and Harford, 1995; Kessler et al., 1996; Swendsen et al., 1998; Degenhardt et al., 2001), less is known about the mental health of non-drinkers. Some recent studies have found ⁎ Corresponding author. Tel.: +61 2 6125 0399; fax: +61 2 6125 0740. E-mail address: [email protected] (B. Rodgers). 0165-0327/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2006.09.006
that self-reported psychological distress is higher in nondrinkers than light or moderate drinkers (Power et al., 1998; Rodgers et al., 2000; Caldwell et al., 2002; Alati et al., 2005). However, a report based on two general population surveys of mental disorders found “no evidence of a U-shaped relationship between lifetime alcohol consumption and lifetime mood and anxiety disorders” (Sareen et al., 2004). Indeed, a greater lifetime prevalence of major depression was reported for moderate drinkers than for lifetime abstainers. The authors emphasised the distinction between transient mood and
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anxiety symptoms that are not necessarily indicative of pathology or psychiatric disorders as determined by reliably structured diagnostic interviews. A difficulty with this account is that symptom measures, including those used in the aforementioned studies, demonstrate substantial temporal stability and good discrimination of individuals with recognised clinical disorders (Rodgers et al., 1999). The present study therefore aimed to investigate the prevalence of affective and anxiety disorders in abstainers compared with light drinkers and to compare these results directly with findings for psychological distress in the same sample. Disorders were identified by a structured diagnostic interview and symptoms assessed by a scale known to discriminate individuals with these disorders. This was feasible using a large survey of mental disorders in the Australian adult population; the Australian National Survey of Mental Health and Wellbeing. 2. Methods The fieldwork for the National Survey of Mental Health and Wellbeing was conducted by the Australian Bureau of Statistics in 1997 (Australian Bureau of Statistics, 1998). 2.1. Sample The target population was adult residents of private dwellings living in all States and Territories of Australia. The sample excluded people living in special dwellings, such as hospitals, institutions, nursing homes, hotels and hostels and also excluded some private dwellings in remote and sparsely populated areas. Overseas visitors, members of non-Australian defence forces and nonAustralian diplomatic personnel were also excluded. The sample was otherwise representative of the resident adult population. In all, 13,624 dwellings were sampled. One person aged 18 years or over was randomly selected from each dwelling to participate in the survey. Participation was voluntary. The achieved sample was 10,641, representing a 78% response rate. Weights for each record were derived using the jackknife method of replicate weighting. 2.2. Data collection and measures Information was gathered by computer-assisted personal interviewing. As well as information on demographic and other social characteristics, the main instrument for data collection was the automated version of the Composite International Diagnostic Interview (CIDI-A; World Health Organization, 1997). Measures of psychological
distress were also obtained during the interview, including the Kessler 10-item psychological distress scale (K10; Andrews and Slade, 2001; Kessler et al., 2002). Only findings based on the K10 scale are reported in this paper, as this has been found to be the measure of distress best predictive of psychiatric diagnoses (Furukawa et al., 2003), but similar results were found for the 12-item version of the General Health Questionnaire (GHQ-12; Goldberg and Williams, 1988) and the mental health scale of the Short Form 12 (SF-12) derived from the Medical Outcomes Study (Ware et al., 1996). In this report, total scores from the K10 are expressed on a scale from 0 to 40, reflecting ratings of the experience of individual symptoms ranging from 0 (none of the time in the past four weeks) to 4 (all of the time in the past 4 weeks). 2.3. Alcohol consumption The alcohol-related disorders module of the CIDI-A begins with the stem question “In the past 12 months, have you had at least 12 drinks of any kind of alcoholic beverage?” This is followed by a second confirmatory question specifically stating that drinking on special occasions or holidays should be included. For those who respond affirmatively, follow-up questions are asked on the typical frequency of drinking over the past 12 months and the typical amount consumed on drinking days, expressed in terms of the number of drinks. The definition of a standard drink in Australia is one containing 10 g or 12.5 ml of ethanol and the number of standard drinks contained in packaged beverages is displayed on bottles, cans and cartons. Familiarity with this labelling is enhanced by references in educational information to permitted alcohol levels for driving. For the present study, an estimate of average weekly consumption was constructed from the CIDI responses, following conventional procedures for quantity–frequency assessment (Shakeshaft et al., 1999). Individuals were classified into four categories of (1) non-drinkers and occasional drinkers (less than 12 drinks in the past year), (2) light drinkers (up to 14 standard drinks per week for men and 7 per week for women), (3) moderate drinkers (up to 28 standard drinks per week for men and 14 per week for women), and (4) those drinking at hazardous or harmful levels (over 28 and 14 standard drinks per week respectively) as defined by the National Health and Medical Research Council of Australia (National Health and Medical Research Council, 2001). Although there is a consensus that the same consumption levels have different consequences for men and women (Graham et al., 1998), doubt remains as to the degree of difference. All analyses in the present study, therefore, used sex as a covariate and included the testing
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of statistical interactions between sex and other independent variables (i.e. age and consumption level). 2.4. Classification of psychiatric disorders Psychiatric disorders were classified by both DSMIV and ICD-10 criteria. Variables representing prevalent disorders (past 12 months) were obtained from computer algorithms applied to the original symptom data collected at interview. The disorders covered by the interview included mood disorders (major depressive disorder, dysthymic disorder and mania) and anxiety disorders (social phobia, agoraphobia, panic disorder, generalised anxiety disorder, obsessive–compulsive disorder, and posttraumatic stress disorder). An additional module covering neurasthenia (ICD-10 diagnosis) was included in the interview (Hickie et al., 2002). 2.5. Statistical analysis Initial data analysis employed the negative binomial model to identify factors associated with continuous outcome measures that have markedly skewed distributions (e.g. the K10). In this model, the coefficient c derived for a predictor variable is more easily interpreted as an incidence rate ratio (IRR) ec that measures the expected change in the dependent variable as a result of one unit change in the predictor variable. Binary logistic regression analyses were used for dichotomous outcome measures (such as CIDI-A diagnoses of mental disorders). Multivariate models included the assessment of interaction terms between independent variables and these were omitted progressively from the models when
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found to be non-significant. Paired contrasts were applied to final models using light drinking groups as reference categories. Analyses were carried out using SPSS 11.5 and STATA 7.0. The latter allowed use of jackknife weights provided with the data to obtain survey estimates conforming to independent estimation of the Australian population at the time of the survey. 3. Results 3.1. Alcohol consumption levels The proportion of individuals falling into the four defined levels of alcohol consumption is shown for each age group and for men and women separately in Table 1, adjusted using sample weights. The proportion of non-/ occasional drinkers varies from 15.0% (in men aged 40– 49) up to 61.4% (in women aged 65 years or more). For most age groups, the rate of non-/occasional drinking in women is at least double that seen for men. Correspondingly, rates of hazardous and harmful drinking are greater in men than women, though this was least evident in the 18–29 age group. The greatest prevalence of hazardous/ harmful consumption was seen in men aged 50–59 (9.9%). For women, the highest rate was in the 60–69 year group (6.5%). For all age groups, in both men and women, light drinking was more prevalent than moderate drinking. 3.2. Psychological distress and prevalence of disorders Table 1 also shows mean K10 scores by age group and sex and the 12-month prevalence of broad categories of
Table 1 Alcohol consumption level (%), mean K10 score, and prevalence of 12-month DSM-IV and ICD-10 affective and anxiety disorders by sex and age group Males 18–29
Females 30–39
40–49
50–59
60–69
70 and 18–29 over
30–39
40–49
50–59
60–69
70 and over
Number 874 1057 986 699 553 442 1181 1341 1127 816 605 754 Weighted N (‘000s) 159.97 138.99 128.56 96.57 66.78 59.54 157.04 141.50 130.23 94.73 68.61 78.98 Alcohol consumption (%) Non-/occasional 15.2 16.5 15.0 16.1 19.0 30.3 26.1 32.5 35.1 39.3 49.8 61.4 Light 68.0 65.5 65.6 62.3 58.4 57.9 60.7 55.8 51.4 46.0 34.9 30.1 Moderate 11.5 11.7 12.2 11.7 14.3 8.3 8.5 8.4 8.5 9.4 8.8 6.7 Hazardous/harmful 5.2 6.3 7.2 9.9 8.3 3.6 4.7 3.4 5.0 5.4 6.5 1.7 K10 score Mean 5.1 5.1 5.1 4.7 4.4 4.9 6.1 5.8 5.7 5.5 4.3 4.3 SD 4.4 4.7 5.4 5.4 5.2 4.7 5.4 5.6 5.6 5.9 4.5 4.3 DSM-IV affective disorders (%) 4.7 6.6 5.6 6.0 2.7 1.0 10.1 9.7 9.3 9.6 5.7 2.3 DSM-IV anxiety disorders (%) 4.5 5.3 5.8 4.7 2.0 1.8 8.5 9.2 6.8 7.1 3.2 1.6 ICD 10 affective disorders (%) 4.4 7.8 6.2 6.3 3.2 1.5 11.5 10.2 10.3 10.1 6.8 2.3 ICD 10 anxiety disorders (%) 8.0 7.9 9.3 8.0 4.7 7.5 13.9 15.3 16.3 15.0 11.0 4.2
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Table 2 Binomial regression model and logistic regression models of K10 scores by sex, age group and consumption level
Predictor variables Sex Female Age groupa 18–29 30–39 40–49 50–59 60–69 Alcohol consumptionb Non-drinkers Moderate Hazardous/harmful
K10 continuous score
K10 score 10 or over
K10 score 20 or over
K10 score 25 or over
Incidence rate ratios (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
1.10 (1.01–1.21)
1.22 (0.97–1.53)
1.12 (0.78–1.59)
1.44 (0.92–2.28)
1.33 (1.22–1.45) 1.28 (1.18–1.39) 1.25 (1.12–1.41) 1.18 (1.07–1.30) 1.00 (0.90–1.11)
1.75 (1.34–2.27) 1.73 (1.35–2.21) 1.72 (1.20–2.47) 1.57 (1.13–2.18) 1.10 (0.80–1.50)
1.04 (0.43–2.49) 1.48 (0.71–3.09) 2.29 (1.15–4.55) 2.29 (0.99–5.33) 1.17 (0.49–2.77)
1.46 (0.31–6.74) 2.91 (0.67–12.61) 3.17 (0.62–16.15) 3.90 (0.77–19.71) 1.68 (0.33–8.63)
1.13 (1.05–1.22) 1.10 (1.02–1.18) 1.36 (1.21–1.52)
1.43 (1.19–1.72) 1.26 (1.03–1.55) 2.14 (1.52–3.02)
2.00 (1.40–2.85) 1.45 (0.60–3.51) 3.44 (2.19–5.41)
2.75 (1.37–5.53) 1.98 (0.61–6.43) 7.13 (3.49–14.60)
a
Compared with those aged 70 and over. Compared with light drinkers.
b
affective disorders and anxiety disorders. Psychological distress scores were highest in the youngest age groups and, except for those aged 60 or more, were higher in women than men. For diagnosed disorders, the prevalence of affective disorders and anxiety disorders was relatively low in those aged 60 or more, but there was not such a clear trend across the younger age groups. The prevalence of both affective and anxiety disorders was higher in women than men (as expected) across age groups, with the exception of anxiety disorders in those aged 70 years and over. 3.3. Psychological distress and alcohol consumption The first column of Table 2 shows IRRs from the negative binomial regression analysis of K10 psycholog-
ical distress scores by sex, age group and level of alcohol consumption. All three independent variables were significantly and independently associated with K10 scores, with no significant interactions. IRR for sex reflects higher distress in women, and IRRs for age group (70 years and over group as comparison) show higher distress in younger age groups (except 60–69 years) with differences increasing with decreasing age. For alcohol consumption, all other groups showed higher distress than light drinkers with the greatest distress evident in hazardous/harmful drinkers. This pattern is further illustrated in the second, third and fourth columns of Table 2 where odds ratios (from logistic regressions) are reported for high K10 scores using cut-points of 10 or more, 20 or more and 25 or more (i.e. approximating the top 10%, 2.5% and 1% of
Table 3 Logistic regression models of DSM-IV and ICD-10 affective and anxiety disorders by sex, age group and consumption level
Predictor variables Sex Female Age groupa 18–29 30–39 40–49 50–59 60–69 Alcohol consumptionb Non-drinkers Moderate Hazardous/harmful a
DSM-IV affective disorders
DSM-IV anxiety disorders
ICD-10 affective disorders
ICD-10 anxiety disorders
Odds ratio (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
1.82 (1.47–2.27)
1.59 (1.13–2.22)
1.84 (1.43–2.38)
1.96 (1.47–2.60)
4.88 (2.82–8.46) 5.37 (2.84–10.18) 4.76 (2.60–8.72) 4.93 (2.81–8.66) 2.50 (1.03–6.09)
4.48 (2.31–8.69) 5.02 (2.96–8.50) 4.19 (2.02–8.70) 3.79 (2.22–6.49) 1.59 (0.84–3.01)
4.75 (2.58–8.75) 5.41 (2.55–11.45) 4.81 (2.42–9.54) 4.66 (2.33–9.35) 2.69 (1.17–6.17)
2.99 (2.02–4.45) 3.20 (2.18–4.69) 3.56 (2.13–5.94) 3.08 (1.86–5.11) 1.98 (1.25–3.14)
1.28 (0.90–1.82) 1.30 (0.89–1.90)) 2.62 (1.93–3.54)
1.39 (0.95–2.01) 1.23 (0.71–2.14) 2.90 (1.97–4.27)
1.28 (0.87–1.88) 1.26 (0.87–1.82) 2.58 (1.99–3.35)
1.15 (0.88–1.50) 1.24 (0.95–1.61) 2.05 (1.53–2.75)
Compared with those aged 70 and over. Compared with light drinkers.
b
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Table 4 Odds ratios for consumption level a from multiple logistic regression models for specific DSM-IV and ICD-10 disorders Depression
Dysthymia
Social Phobia
Agoraphobia Panic disorder
GAD
OCD
PTSD
Neurasthenia
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
2.86 (1.47–5.56) 2.06 (0.58–7.31) 5.63 (2.95–10.74)
1.77 (0.84–3.73) 0.98 (0.25–3.93) 2.31 (1.32–4.03)
1.30 (0.48–3.47) 0.90 (0.19–4.19) 3.32 (0.58–18.91)
1.06 (0.61–1.85) 1.10 (0.48–2.53) 3.61 (1.51–8.62)
1.18 (0.69–2.03) 1.59 (0.76–3.32) 2.70 (1.56–4.69)
1.61 (0.93–2.80) 0.82 (0.16–4.26) 1.66 (0.43–6.44)
2.17 n.a. (1.22–3.87) 1.31 n.a. (0.64–2.67) 4.87 n.a. (3.20–7.40)
2.29 (1.12–4.66) 1.50 (0.50–4.55) 4.14 (2.21–7.75)
1.09 (0.74–1.61) 1.31 (0.71–2.41) 1.36 (0.72–2.57)
1.94 (1.03–3.66) 1.80 (0.63–5.18) 4.34 (1.93–9.76)
0.98 (0.63–1.54) 1.14 (0.61–2.13) 1.14 (0.62–2.09)
1.18 (0.89–1.56) 1.25 (0.81–1.95) 2.36 (1.45–3.83)
1.72 (0.78–3.79) 1.02 (0.06–17.07) 3.01 (0.68–13.43)
1.50 (0.88–2.54) 0.88 (0.51–1.51) 2.41 (1.41–4.14)
DSM-IV diagnoses 1.23 Non-drinkers (0.91–1.66) Moderate 1.29 (0.85–1.96) Hazardous/ 2.57 harmful (2.02–3.26) ICD-10 diagnoses Non-drinkers 1.23 (0.89–1.71) Moderate 1.27 (0.82–1.97) Hazardous/ 2.54 harmful (1.98–3.26) a
1.67 (0.83–3.39) 0.97 (0.45–2.09) 1.99 (1.13–3.52)
Compared with light drinkers.
scores respectively). Odds ratios are significantly greater than 1.0 for both non-/occasional drinkers and hazardous/harmful drinkers relative to light drinkers, across all three cut-points.
non-drinkers were greater than 1.0 (e.g. 1.61 for DSM-IV obsessive–compulsive disorder and 1.67 for ICD-10 neurasthenia) but not significantly so. 4. Discussion
3.4. Psychiatric disorders and alcohol consumption 4.1. Summary of findings Table 3 shows odds ratios, with 95% confidence intervals, for broad categories of affective and anxiety disorders (DSM-IV and ICD-10 criteria) by age, sex and consumption level. These confirm higher rates of disorder in women and in younger age groups. With regard to alcohol consumption, only the odds ratios for those drinking at hazardous/harmful levels were significantly different from light drinkers, with between double and three times the likelihood of diagnosed disorder. There were trends towards non-/occasional drinkers and moderate drinkers having greater risk of diagnosed disorder, but the indicated odds ratios (range 1.15 to 1.39) were not significant at the 0.05 level. Table 4 shows odds ratios from multiple logistic regression analyses for specific DSM-IV and ICD-10 diagnoses with light drinkers as the reference category. Most odds ratios for the hazardous/harmful category were significantly greater than 1.0, with trends in the same direction when not significant. For the non-/occasional drinkers, odds ratios were only significantly elevated for dysthymia (both DSM-IV and ICD-10 diagnoses), agoraphobia (ICD-10 only), and posttraumatic stress disorder (DSM-IVonly). Some other odds ratios for the occasional/
The findings from this large nationally representative sample confirmed previous results showing Jshaped and U-shaped relationships between psychological distress and alcohol consumption levels (Power et al., 1998; Rodgers et al., 2000; Caldwell et al., 2002). Hazardous/harmful drinkers (over 40 g alcohol per day for men and 20 g per day for women) had the greatest likelihood of high distress scores on the K10 scale. Non-drinkers and occasional drinkers (less than 12 drinks in the past year) also had higher distress levels compared to light drinkers (less than 20 g alcohol per day for men and 10 g per day for women). The risk of high distress was not as great for non-/occasional drinkers as it was for the hazardous/harmful drinkers. Using the example of distress scores falling into the top 2.5% for the population (K10 score of 20 or more), odds ratios were 2.00 for non-/occasional drinkers and 3.44 for hazardous/harmful drinkers, indicating a Jshaped relationship. Findings for disorders by DSM-IVand ICD-10 criteria provided clear results only in hazardous/harmful drinkers, with consistently elevated odds ratios for any affective
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disorder, any anxiety disorder, and for more specific diagnoses, confirming our expectations from many previous studies (Regier et al., 1990; Dick et al., 1994; Grant and Harford, 1995; Kessler et al., 1996; Swendsen et al., 1998; Degenhardt et al., 2001). By contrast, odds ratios for non-/occasional drinkers were significantly greater than 1.0 only for dysthymia (ICD-10 and DSM-IV diagnoses), agoraphobia (ICD-10 only), and posttraumatic stress disorder (DSM-IV only). J-shaped relationships were less evident for diagnosed disorders than for high distress scores. However, the present study did not find any increased risk for disorder in light or moderate drinkers, compared with abstainers, as reported by Sareen et al. (2004) for major depression. 4.2. Limitations Could differences in findings relating to psychological distress on the one hand, and to diagnosed disorders on the other, be due to methodological limitations? One limitation is that non-significant findings for specific disorders may reflect reduced statistical power, particularly for low prevalence disorders such as obsessive–compulsive disorder. This, however, cannot account for the non-significant findings for relatively prevalent broad groupings of affective disorders and anxiety disorders when comparing between non-/occasional drinkers and light drinkers. Nor is limited statistical power evident for very high distress levels on the K10 (i.e. score greater than 25) which are found in only 1% of the sample. A significant difference between non-/occasional drinkers and light drinkers (OR 2.75) was found for these very high distress levels (Table 2). A second limitation is that alcohol consumption history was not collected. It would be desirable to investigate the role of past consumption in the relationships between mental health and alcohol use, but this offers no ready explanation as to why U- or J-shaped findings should be more prominent for distress than for diagnosed disorders. Furthermore, the common perception that current abstainers especially include a significant proportion of previous problem drinkers is not supported by reports that moderate drinkers are more likely to have been heavy drinkers in the past than are non-drinkers (Goldman and Najman, 1984; Power et al., 1998; Caldwell et al., 2002). Indeed, previous studies that have taken account of past drinking levels have failed to account for U- or J-shaped relationships (Power et al., 1998; Alati et al., 2005), and statistical adjustments for past heavy drinking have even exacerbated the heightened distress found in non-/occasional drinkers compared with light drinkers (Caldwell et al., 2002).
A third limitation is the finite validity of measures and this could apply to the K10 scale and the diagnoses from the CIDI-A. Clearly, these are not perfect measures but evidence indicates, for both the K10 (Kessler et al., 2002) and the CIDI (Wittchen, 1994; Kessler et al., 1998), that they are as good as (and most likely superior to) other instruments of their type. Most importantly, there is strong evidence supporting the relationship between the two measures, particularly the capacity of the K10 to discriminate individuals with affective and anxiety disorders (Andrews and Slade, 2001; Kessler et al., 2002, 2003; Furukawa et al., 2003). The prevalence of DSM-IV disorders (previous 12 months) has been shown to increase from 10.4% for K10 scores in the range 0 to 4, through 48.5% for scores of 10 to 14, to 94.0% for scores above 30, in the same sample as reported on here (Andrews and Slade, 2001). A general distinction between apparently transient symptoms and diagnosed disorders (Sareen et al., 2004) is not evident in this sample as a whole and our own findings demonstrate that it is not a useful distinction in the case of heavy drinkers. The idea that measures of general psychological distress are not accurate indicators of diagnosed affective and anxiety disorders cannot, therefore, be used to explain Sareen et al.'s (2004) findings of no elevated prevalence of diagnosed disorders in non-drinkers compared with moderate drinkers. A further limitation is that the sample was restricted to the residential population and excluded those living in hospitals, institutions, nursing homes, hotels and hostels and omitted the homeless. People with comorbid alcohol and other mental health problems may well be underrepresented in the sample and it is also possible that some of these missing groups are characterised by non-drinking in combination with mental health problems. These exclusions are likely to have reduced the strength of reported J-shaped relationships. 4.3. Do non-drinkers and heavy drinkers have different symptom profiles? The psychological distress found in non-/occasional drinkers most probably represents true elevation of a range of symptoms relative to light drinkers, but this symptomatology does not necessarily meet criteria for many affective and anxiety disorders. There was no significant elevation of risk for more prevalent disorders (depressive disorder, generalised anxiety disorder and panic disorder) in non-/occasional drinkers compared with light drinkers, as observed for high K10 scores. Increased risk for low prevalence disorders (e.g. obsessive–compulsive disorder) in abstainers can neither be
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confirmed nor ruled out by the present study because of power limitations. For disorders of intermediate prevalence (dysthymia, social phobia, agoraphobia, PTSD, and neurasthenia), variations in findings across different disorders and between results for the two classificatory systems could well have arisen by chance (Table 4). ORs were typically greater than 1.0 for non-/occasional drinkers (16 out of a total of 17 analyses), which does not support the idea of a dose–response relationship between prevalence of disorder and consumption level. Accepting the null hypothesis (same prevalence of disorder in non-/ occasional drinkers compared to light drinkers) on the basis of non-significant findings carries risk of Type 2 error and replication is therefore needed to provide more precise estimates. Investigating the full constellation of symptoms reported by non-drinkers would be more informative than contrasting their diagnoses with other drinking groups. Unfortunately, the structure of the CIDI-A in the present study precluded a comprehensive analysis of this sort, as skips are utilised throughout the interview and most respondents are required to answer only a minority of questions. 4.4. Possible explanations for increased distress and disorder in abstainers Setting aside differences in findings between measures of distress and disorder, the question remains as to why abstainers might have increased prevalence of high distress and some disorders compared to light drinkers. These observations are significant in their own right, as non-drinkers constitute a larger part of the population than heavy drinkers. They may also contribute to similar documented patterns for physical health and mortality (Shaper, 1990; Marmot and Brunner, 1991; Poikolainen, 1995; Fillmore, 2000). One possible answer is that light to moderate alcohol consumption has a general protective influence on health and wellbeing. This protective effect may be attributable to social circumstances surrounding drinking as distinct from benefits of alcohol ingestion. Second, abstainers could have personal or social background characteristics, such as poorer social support, that predispose to distress and some specific disorders (Rodgers et al., 2000; Caldwell et al., 2002), and the present findings for agoraphobia may be an extreme example of this association. Longitudinal studies will be needed to determine whether such risk factors in abstainers precede increases in distress or onset of disorder. A third possibility is that chronic or recent-onset distress or disorder may lead to giving up drinking (the “sick
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quitter” hypothesis) or to not taking up drinking in the first place. One variant of this account is the discouragement of alcohol use for those prescribed certain medications. This seems unlikely to be a major factor in the present study, where J-shaped relationships were less evident for diagnoses than for distress and were more pronounced for dysthymia than depressive disorder. Practice appears variable for prescribed psychotropics, with complete abstention being indicated for some medications and, where there is discretion, with some clinicians recommending moderation of alcohol use and others recommending complete abstention. To what extent patients follow such advice is difficult to ascertain. A second variant of this account would apply to circumstances where alcohol-related life events, such as motor vehicle accidents, could lead to both onset of disorder (e.g. PTSD) and to giving up drinking. Longitudinal data will be required to examine the sick–quitter hypothesis more thoroughly, including whether use of prescribed medications or onset of specific disorders affect drinking behaviour. A fourth explanation is that onset of some disorders (e.g. PTSD) may increase the amount of alcohol consumed by those who already drink, without changing the behaviour of abstainers. This would polarize drinking levels in those with disorders, manifesting as reduced levels of distress and disorder in light and moderate drinkers. Again, longitudinal data will be required to investigate this hypothesis thoroughly. 4.5. Conclusions Although further investigation is needed of associations of distress and disorder with non-drinking, a number of conclusions can be drawn from the present study. First, we have provided confirmation, from a large nationally representative sample, of J-shaped relationships between psychological distress and alcohol consumption. Second, we have established that associations between prevalence of specific affective and anxiety disorders and current alcohol consumption do not follow dose–response relationships. Consequently, investigations in this field should consider the whole spectrum of consumption rather than focus on heavy drinkers or problem drinkers. Third, there is new evidence that non-/occasional drinkers are at increased risk for some specific disorders compared to light drinkers. Fourth, the study presents a testable hypothesis that non-/occasional drinkers not only report lower overall levels of psychological distress compared to heavy drinkers but also that their pattern of symptomatology is of a different character.
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Acknowledgements This work was supported by Program Grant No. 179805 from the National Health and Medical Research Council of Australia. Bryan Rodgers has been supported by NHMRC Research Fellowships No. 148948 and No. 366758. The National Drug and Alcohol Research Centre is funded by the Australian Government Department of Health and Ageing. The authors are grateful to the two anonymous reviewers who provided very useful feedback on an earlier draft of the manuscript. References Alati, R., Lawlor, D.A., Najman, J.M., Williams, G.D., Bor, W., O'Callaghan, M.J., 2005. Is there really a ‘J-shaped’ curve in the association between alcohol consumption and symptoms of depression and anxiety? Findings from the Mater-University Study of Pregnancy and its outcomes. Addiction 100, 643–651. Andrews, G., Slade, T., 2001. Interpreting scores on the Kessler Psychological Distress Scale (K10). Aust. N. Z. J. Public Health 25, 494–497. Australian Bureau of Statistics, 1998. Mental Health and Wellbeing: Profile of Adults, Australia. Cat. No. 4326.0. ABS, Canberra. Caldwell, T.M., Rodgers, B., Jorm, A.F., Christensen, H., Jacomb, P.A., Korten, A.E., Lynskey, M.T., 2002. Patterns of association between alcohol consumption and symptoms of depression and anxiety in young adults. Addiction 97, 583–594. Degenhardt, L.J., Hall, W., Lynskey, M., 2001. Alcohol, cannabis and tobacco use among Australians: a comparison of their associations with other drug use and use disorders, affective and anxiety disorders, and psychosis. Addiction 96, 1603–1614. Dick, C.L., Sowa, B., Bland, R.C., Newman, S.C., 1994. Epidemiology of psychiatric disorders in Edmonton. Phobic disorders. Acta Psychiatr. Scand., Suppl. 376, 36–44. Fillmore, M.K., 2000. Is alcohol really good for the heart? Addiction 95, 173–174. Furukawa, T.A., Kessler, R.C., Slade, T., Andrews, G., 2003. The performance of the K6 and K10 screening scales for psychological distress in the Australian National Survey of Mental Health and Well-Being. Psychol. Med. 33, 357–362. Goldberg, D., Williams, P., 1988. A User's Guide to the General Health Questionnaire. NFER-Nelson, Windsor. Goldman, E., Najman, J.M., 1984. Lifetime abstainers, current abstainers and imbibers: a methodological note. Br. J. Addict. 79, 309–314. Graham, K., Wilsnack, R., Dawson, D., Vogeltanz, N., 1998. Should alcohol consumption measures be adjusted for gender differences? Addiction 93, 1137–1147. Grant, B.F., Harford, T.C., 1995. Comorbidity between DSM-IV alcohol use disorders and major depression: results of a national survey. Drug Alcohol Depend. 39, 197–206. Hickie, I., Davenport, T., Issakidis, C., Andrews, G., 2002. Neurasthenia: prevalence, disability and health care characteristics in the Australian community. Br. J. Psychiatry 181, 56–61.
Kessler, R.C., Nelson, C.B., McGonagle, K.A., Edlund, M.J., Frank, R.G., Leaf, P.J., 1996. The epidemiology of co-occurring addictive and mental disorders: implications for prevention and service utilization. Am. J. Orthopsychiatr. 66, 17–31. Kessler, R.C., Wittchen, H.U., Abelson, J.M., McGonagle, K., Schwarz, N., Kendler, S.K., Knäuper, B., Zhao, S., 1998. Methodological studies of the Composite International Diagnostic Interview (CIDI) in the US National Comorbidity Survey (NCS). Int. J. Methods Psychiatr. Res. 7, 33–54. Kessler, R.C., Andrews, G., Colpe, L.J., Hiripi, E., Mroczek, D.K., Normand, S.-L.T., Walters, E.E., Zaslsvsky, A.M., 2002. Short screening scales to monitor population prevalences and trends in non-specific psychological distress. Psychol. Med. 32, 959–976. Kessler, R.C., Barker, P.R., Colpe, L.J., Epstein, J.F., Gfroerer, J.C., Hiripi, E., Howes, M.J., Normand, S.-L.T., Manderscheid, R.W., Walters, E.E., Zaslavsky, A.M., 2003. Screening for serious mental illness in the general population. Arch. Gen. Psychiatry 60, 184–189. Marmot, M., Brunner, E., 1991. Alcohol and cardiovascular disease: the status of the U shaped curve. Br. Med. J. 303, 565–568. National Health and Medical Research Council, 2001. Australian Alcohol Guidelines: Health Risks and Benefits. NHMRC, Canberra. Poikolainen, K., 1995. Alcohol and mortality: a review. J. Clin. Epidemiol. 48, 455–465. Power, C., Rodgers, B., Hope, S., 1998. U-shaped relation for alcohol consumption and health in early adulthood and implications for mortality (research letter). Lancet 352, 877. Regier, D.A., Farmer, M.E., Rae, D.S., Locke, B.Z., Keith, S.J., Judd, L.L., Goodwin, F.K., 1990. Comorbidity of mental disorders with alcohol and other drug abuse: results from the Epidemiologic Catchment Area (ECA) Study. JAMA 264, 2511–2518. Rodgers, B., Pickles, A., Power, C., Collishaw, S., Maughan, B., 1999. Validity of the Malaise Inventory in general population samples. Soc. Psychiatry Psychiatr. Epidemiol. 34, 333–341. Rodgers, B., Korten, A.E., Jorm, A.F., Jacomb, P.A., Christensen, H., Henderson, S., 2000. Non-linear relationships in associations of depression and anxiety with alcohol use. Psychol. Med. 30, 421–432. Sareen, J., McWilliams, L., Cox, B., Stein, M.B., 2004. Does a Ushaped relationship exist between alcohol use and DSM-III-R mood and anxiety disorders? J. Affect. Disord. 82, 113–118. Shakeshaft, A.P., Bowman, J.A., Sanson-Fisher, R.W., 1999. A comparison of two retrospective measures of weekly alcohol consumption: diary and quantity/frequency index. Alcohol Alcohol. 34, 636–645. Shaper, A.G., 1990. Alcohol and mortality: a review of prospective studies. Br. J. Addict. 85, 837–847. Swendsen, J.D., Merikangas, K.R., Canino, G.J., Kessler, R.C., RubioStipec, M., Angst, J., 1998. The comorbidity of alcoholism with anxiety and depressive disorders in four geographic communities. Compr. Psychiatry 39, 176–184. Ware, J.E., Kosinski, M., Keller, S.D., 1996. A 12-item short-form health survey: construction of scales and preliminary tests of reliability and validity. Med. Care 34, 220–233. Wittchen, H.-U., 1994. Reliability and validity studies of the WHO Composite International Diagnostic Interview (CIDI): a critical review. J. Psychiatr. Res. 28, 57–84. World Health Organization, 1997. Composite International Diagnostic Interview, Version 2.1. WHO, Geneva.
Research report
Affective disorders, anxiety disorders and psychological distress in non-drinkers Bryan Rodgers a,⁎, Ruth Parslow b , Louisa Degenhardt c a
National Centre for Epidemiology and Population Health, The Australian National University, Canberra ACT 0200, Australia b Orygen Research Centre, University of Melbourne, Australia c National Drug and Alcohol Research Centre, University of New South Wales, Sydney, Australia Received 4 July 2005; received in revised form 5 September 2006; accepted 6 September 2006 Available online 12 October 2006
Abstract Background: Non-drinkers have elevated levels of psychological distress but a recent study reported no elevation in prevalence of diagnosed disorders. We aimed to determine the prevalence of affective and anxiety disorders (from the CIDI-A) in current abstainers and contrast results with findings for psychological distress (K10) in the same sample. Methods: Cross-sectional, representative household survey of adult Australians. Results: Non-/occasional drinkers had higher levels of psychological distress than light drinkers, and distress in heavy drinkers was even higher. Heavy drinkers also had the highest rates of most disorders. Non-/occasional drinkers showed significantly elevated prevalence only of dysthymia, agoraphobia and posttraumatic stress disorder compared with light drinkers. Limitations: Statistical power was limited for investigating low prevalence disorders. History of alcohol consumption was not collected. The CIDI-A and K10 have finite validity. Conclusions: This study confirmed J-shaped relationships between psychological distress and alcohol consumption. Although affective and anxiety disorders also showed non-linear relationships with alcohol consumption, non-/occasional drinkers are not at increased risk for all disorders compared to light drinkers. The pattern of symptomatology in non-/occasional drinkers may be of a different character to that in heavy drinkers, as well as being less severe. © 2006 Elsevier B.V. All rights reserved. Keywords: Depression; Anxiety; Alcohol drinking; Temperance; Comorbidity
1. Introduction Although many reports indicate a high prevalence of affective and anxiety disorders in people with alcohol use disorders (Regier et al., 1990; Dick et al., 1994; Grant and Harford, 1995; Kessler et al., 1996; Swendsen et al., 1998; Degenhardt et al., 2001), less is known about the mental health of non-drinkers. Some recent studies have found ⁎ Corresponding author. Tel.: +61 2 6125 0399; fax: +61 2 6125 0740. E-mail address: [email protected] (B. Rodgers). 0165-0327/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2006.09.006
that self-reported psychological distress is higher in nondrinkers than light or moderate drinkers (Power et al., 1998; Rodgers et al., 2000; Caldwell et al., 2002; Alati et al., 2005). However, a report based on two general population surveys of mental disorders found “no evidence of a U-shaped relationship between lifetime alcohol consumption and lifetime mood and anxiety disorders” (Sareen et al., 2004). Indeed, a greater lifetime prevalence of major depression was reported for moderate drinkers than for lifetime abstainers. The authors emphasised the distinction between transient mood and
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anxiety symptoms that are not necessarily indicative of pathology or psychiatric disorders as determined by reliably structured diagnostic interviews. A difficulty with this account is that symptom measures, including those used in the aforementioned studies, demonstrate substantial temporal stability and good discrimination of individuals with recognised clinical disorders (Rodgers et al., 1999). The present study therefore aimed to investigate the prevalence of affective and anxiety disorders in abstainers compared with light drinkers and to compare these results directly with findings for psychological distress in the same sample. Disorders were identified by a structured diagnostic interview and symptoms assessed by a scale known to discriminate individuals with these disorders. This was feasible using a large survey of mental disorders in the Australian adult population; the Australian National Survey of Mental Health and Wellbeing. 2. Methods The fieldwork for the National Survey of Mental Health and Wellbeing was conducted by the Australian Bureau of Statistics in 1997 (Australian Bureau of Statistics, 1998). 2.1. Sample The target population was adult residents of private dwellings living in all States and Territories of Australia. The sample excluded people living in special dwellings, such as hospitals, institutions, nursing homes, hotels and hostels and also excluded some private dwellings in remote and sparsely populated areas. Overseas visitors, members of non-Australian defence forces and nonAustralian diplomatic personnel were also excluded. The sample was otherwise representative of the resident adult population. In all, 13,624 dwellings were sampled. One person aged 18 years or over was randomly selected from each dwelling to participate in the survey. Participation was voluntary. The achieved sample was 10,641, representing a 78% response rate. Weights for each record were derived using the jackknife method of replicate weighting. 2.2. Data collection and measures Information was gathered by computer-assisted personal interviewing. As well as information on demographic and other social characteristics, the main instrument for data collection was the automated version of the Composite International Diagnostic Interview (CIDI-A; World Health Organization, 1997). Measures of psychological
distress were also obtained during the interview, including the Kessler 10-item psychological distress scale (K10; Andrews and Slade, 2001; Kessler et al., 2002). Only findings based on the K10 scale are reported in this paper, as this has been found to be the measure of distress best predictive of psychiatric diagnoses (Furukawa et al., 2003), but similar results were found for the 12-item version of the General Health Questionnaire (GHQ-12; Goldberg and Williams, 1988) and the mental health scale of the Short Form 12 (SF-12) derived from the Medical Outcomes Study (Ware et al., 1996). In this report, total scores from the K10 are expressed on a scale from 0 to 40, reflecting ratings of the experience of individual symptoms ranging from 0 (none of the time in the past four weeks) to 4 (all of the time in the past 4 weeks). 2.3. Alcohol consumption The alcohol-related disorders module of the CIDI-A begins with the stem question “In the past 12 months, have you had at least 12 drinks of any kind of alcoholic beverage?” This is followed by a second confirmatory question specifically stating that drinking on special occasions or holidays should be included. For those who respond affirmatively, follow-up questions are asked on the typical frequency of drinking over the past 12 months and the typical amount consumed on drinking days, expressed in terms of the number of drinks. The definition of a standard drink in Australia is one containing 10 g or 12.5 ml of ethanol and the number of standard drinks contained in packaged beverages is displayed on bottles, cans and cartons. Familiarity with this labelling is enhanced by references in educational information to permitted alcohol levels for driving. For the present study, an estimate of average weekly consumption was constructed from the CIDI responses, following conventional procedures for quantity–frequency assessment (Shakeshaft et al., 1999). Individuals were classified into four categories of (1) non-drinkers and occasional drinkers (less than 12 drinks in the past year), (2) light drinkers (up to 14 standard drinks per week for men and 7 per week for women), (3) moderate drinkers (up to 28 standard drinks per week for men and 14 per week for women), and (4) those drinking at hazardous or harmful levels (over 28 and 14 standard drinks per week respectively) as defined by the National Health and Medical Research Council of Australia (National Health and Medical Research Council, 2001). Although there is a consensus that the same consumption levels have different consequences for men and women (Graham et al., 1998), doubt remains as to the degree of difference. All analyses in the present study, therefore, used sex as a covariate and included the testing
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of statistical interactions between sex and other independent variables (i.e. age and consumption level). 2.4. Classification of psychiatric disorders Psychiatric disorders were classified by both DSMIV and ICD-10 criteria. Variables representing prevalent disorders (past 12 months) were obtained from computer algorithms applied to the original symptom data collected at interview. The disorders covered by the interview included mood disorders (major depressive disorder, dysthymic disorder and mania) and anxiety disorders (social phobia, agoraphobia, panic disorder, generalised anxiety disorder, obsessive–compulsive disorder, and posttraumatic stress disorder). An additional module covering neurasthenia (ICD-10 diagnosis) was included in the interview (Hickie et al., 2002). 2.5. Statistical analysis Initial data analysis employed the negative binomial model to identify factors associated with continuous outcome measures that have markedly skewed distributions (e.g. the K10). In this model, the coefficient c derived for a predictor variable is more easily interpreted as an incidence rate ratio (IRR) ec that measures the expected change in the dependent variable as a result of one unit change in the predictor variable. Binary logistic regression analyses were used for dichotomous outcome measures (such as CIDI-A diagnoses of mental disorders). Multivariate models included the assessment of interaction terms between independent variables and these were omitted progressively from the models when
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found to be non-significant. Paired contrasts were applied to final models using light drinking groups as reference categories. Analyses were carried out using SPSS 11.5 and STATA 7.0. The latter allowed use of jackknife weights provided with the data to obtain survey estimates conforming to independent estimation of the Australian population at the time of the survey. 3. Results 3.1. Alcohol consumption levels The proportion of individuals falling into the four defined levels of alcohol consumption is shown for each age group and for men and women separately in Table 1, adjusted using sample weights. The proportion of non-/ occasional drinkers varies from 15.0% (in men aged 40– 49) up to 61.4% (in women aged 65 years or more). For most age groups, the rate of non-/occasional drinking in women is at least double that seen for men. Correspondingly, rates of hazardous and harmful drinking are greater in men than women, though this was least evident in the 18–29 age group. The greatest prevalence of hazardous/ harmful consumption was seen in men aged 50–59 (9.9%). For women, the highest rate was in the 60–69 year group (6.5%). For all age groups, in both men and women, light drinking was more prevalent than moderate drinking. 3.2. Psychological distress and prevalence of disorders Table 1 also shows mean K10 scores by age group and sex and the 12-month prevalence of broad categories of
Table 1 Alcohol consumption level (%), mean K10 score, and prevalence of 12-month DSM-IV and ICD-10 affective and anxiety disorders by sex and age group Males 18–29
Females 30–39
40–49
50–59
60–69
70 and 18–29 over
30–39
40–49
50–59
60–69
70 and over
Number 874 1057 986 699 553 442 1181 1341 1127 816 605 754 Weighted N (‘000s) 159.97 138.99 128.56 96.57 66.78 59.54 157.04 141.50 130.23 94.73 68.61 78.98 Alcohol consumption (%) Non-/occasional 15.2 16.5 15.0 16.1 19.0 30.3 26.1 32.5 35.1 39.3 49.8 61.4 Light 68.0 65.5 65.6 62.3 58.4 57.9 60.7 55.8 51.4 46.0 34.9 30.1 Moderate 11.5 11.7 12.2 11.7 14.3 8.3 8.5 8.4 8.5 9.4 8.8 6.7 Hazardous/harmful 5.2 6.3 7.2 9.9 8.3 3.6 4.7 3.4 5.0 5.4 6.5 1.7 K10 score Mean 5.1 5.1 5.1 4.7 4.4 4.9 6.1 5.8 5.7 5.5 4.3 4.3 SD 4.4 4.7 5.4 5.4 5.2 4.7 5.4 5.6 5.6 5.9 4.5 4.3 DSM-IV affective disorders (%) 4.7 6.6 5.6 6.0 2.7 1.0 10.1 9.7 9.3 9.6 5.7 2.3 DSM-IV anxiety disorders (%) 4.5 5.3 5.8 4.7 2.0 1.8 8.5 9.2 6.8 7.1 3.2 1.6 ICD 10 affective disorders (%) 4.4 7.8 6.2 6.3 3.2 1.5 11.5 10.2 10.3 10.1 6.8 2.3 ICD 10 anxiety disorders (%) 8.0 7.9 9.3 8.0 4.7 7.5 13.9 15.3 16.3 15.0 11.0 4.2
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Table 2 Binomial regression model and logistic regression models of K10 scores by sex, age group and consumption level
Predictor variables Sex Female Age groupa 18–29 30–39 40–49 50–59 60–69 Alcohol consumptionb Non-drinkers Moderate Hazardous/harmful
K10 continuous score
K10 score 10 or over
K10 score 20 or over
K10 score 25 or over
Incidence rate ratios (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
1.10 (1.01–1.21)
1.22 (0.97–1.53)
1.12 (0.78–1.59)
1.44 (0.92–2.28)
1.33 (1.22–1.45) 1.28 (1.18–1.39) 1.25 (1.12–1.41) 1.18 (1.07–1.30) 1.00 (0.90–1.11)
1.75 (1.34–2.27) 1.73 (1.35–2.21) 1.72 (1.20–2.47) 1.57 (1.13–2.18) 1.10 (0.80–1.50)
1.04 (0.43–2.49) 1.48 (0.71–3.09) 2.29 (1.15–4.55) 2.29 (0.99–5.33) 1.17 (0.49–2.77)
1.46 (0.31–6.74) 2.91 (0.67–12.61) 3.17 (0.62–16.15) 3.90 (0.77–19.71) 1.68 (0.33–8.63)
1.13 (1.05–1.22) 1.10 (1.02–1.18) 1.36 (1.21–1.52)
1.43 (1.19–1.72) 1.26 (1.03–1.55) 2.14 (1.52–3.02)
2.00 (1.40–2.85) 1.45 (0.60–3.51) 3.44 (2.19–5.41)
2.75 (1.37–5.53) 1.98 (0.61–6.43) 7.13 (3.49–14.60)
a
Compared with those aged 70 and over. Compared with light drinkers.
b
affective disorders and anxiety disorders. Psychological distress scores were highest in the youngest age groups and, except for those aged 60 or more, were higher in women than men. For diagnosed disorders, the prevalence of affective disorders and anxiety disorders was relatively low in those aged 60 or more, but there was not such a clear trend across the younger age groups. The prevalence of both affective and anxiety disorders was higher in women than men (as expected) across age groups, with the exception of anxiety disorders in those aged 70 years and over. 3.3. Psychological distress and alcohol consumption The first column of Table 2 shows IRRs from the negative binomial regression analysis of K10 psycholog-
ical distress scores by sex, age group and level of alcohol consumption. All three independent variables were significantly and independently associated with K10 scores, with no significant interactions. IRR for sex reflects higher distress in women, and IRRs for age group (70 years and over group as comparison) show higher distress in younger age groups (except 60–69 years) with differences increasing with decreasing age. For alcohol consumption, all other groups showed higher distress than light drinkers with the greatest distress evident in hazardous/harmful drinkers. This pattern is further illustrated in the second, third and fourth columns of Table 2 where odds ratios (from logistic regressions) are reported for high K10 scores using cut-points of 10 or more, 20 or more and 25 or more (i.e. approximating the top 10%, 2.5% and 1% of
Table 3 Logistic regression models of DSM-IV and ICD-10 affective and anxiety disorders by sex, age group and consumption level
Predictor variables Sex Female Age groupa 18–29 30–39 40–49 50–59 60–69 Alcohol consumptionb Non-drinkers Moderate Hazardous/harmful a
DSM-IV affective disorders
DSM-IV anxiety disorders
ICD-10 affective disorders
ICD-10 anxiety disorders
Odds ratio (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
Odds ratio (95% CI)
1.82 (1.47–2.27)
1.59 (1.13–2.22)
1.84 (1.43–2.38)
1.96 (1.47–2.60)
4.88 (2.82–8.46) 5.37 (2.84–10.18) 4.76 (2.60–8.72) 4.93 (2.81–8.66) 2.50 (1.03–6.09)
4.48 (2.31–8.69) 5.02 (2.96–8.50) 4.19 (2.02–8.70) 3.79 (2.22–6.49) 1.59 (0.84–3.01)
4.75 (2.58–8.75) 5.41 (2.55–11.45) 4.81 (2.42–9.54) 4.66 (2.33–9.35) 2.69 (1.17–6.17)
2.99 (2.02–4.45) 3.20 (2.18–4.69) 3.56 (2.13–5.94) 3.08 (1.86–5.11) 1.98 (1.25–3.14)
1.28 (0.90–1.82) 1.30 (0.89–1.90)) 2.62 (1.93–3.54)
1.39 (0.95–2.01) 1.23 (0.71–2.14) 2.90 (1.97–4.27)
1.28 (0.87–1.88) 1.26 (0.87–1.82) 2.58 (1.99–3.35)
1.15 (0.88–1.50) 1.24 (0.95–1.61) 2.05 (1.53–2.75)
Compared with those aged 70 and over. Compared with light drinkers.
b
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Table 4 Odds ratios for consumption level a from multiple logistic regression models for specific DSM-IV and ICD-10 disorders Depression
Dysthymia
Social Phobia
Agoraphobia Panic disorder
GAD
OCD
PTSD
Neurasthenia
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
Odds ratio
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
(95% CI)
2.86 (1.47–5.56) 2.06 (0.58–7.31) 5.63 (2.95–10.74)
1.77 (0.84–3.73) 0.98 (0.25–3.93) 2.31 (1.32–4.03)
1.30 (0.48–3.47) 0.90 (0.19–4.19) 3.32 (0.58–18.91)
1.06 (0.61–1.85) 1.10 (0.48–2.53) 3.61 (1.51–8.62)
1.18 (0.69–2.03) 1.59 (0.76–3.32) 2.70 (1.56–4.69)
1.61 (0.93–2.80) 0.82 (0.16–4.26) 1.66 (0.43–6.44)
2.17 n.a. (1.22–3.87) 1.31 n.a. (0.64–2.67) 4.87 n.a. (3.20–7.40)
2.29 (1.12–4.66) 1.50 (0.50–4.55) 4.14 (2.21–7.75)
1.09 (0.74–1.61) 1.31 (0.71–2.41) 1.36 (0.72–2.57)
1.94 (1.03–3.66) 1.80 (0.63–5.18) 4.34 (1.93–9.76)
0.98 (0.63–1.54) 1.14 (0.61–2.13) 1.14 (0.62–2.09)
1.18 (0.89–1.56) 1.25 (0.81–1.95) 2.36 (1.45–3.83)
1.72 (0.78–3.79) 1.02 (0.06–17.07) 3.01 (0.68–13.43)
1.50 (0.88–2.54) 0.88 (0.51–1.51) 2.41 (1.41–4.14)
DSM-IV diagnoses 1.23 Non-drinkers (0.91–1.66) Moderate 1.29 (0.85–1.96) Hazardous/ 2.57 harmful (2.02–3.26) ICD-10 diagnoses Non-drinkers 1.23 (0.89–1.71) Moderate 1.27 (0.82–1.97) Hazardous/ 2.54 harmful (1.98–3.26) a
1.67 (0.83–3.39) 0.97 (0.45–2.09) 1.99 (1.13–3.52)
Compared with light drinkers.
scores respectively). Odds ratios are significantly greater than 1.0 for both non-/occasional drinkers and hazardous/harmful drinkers relative to light drinkers, across all three cut-points.
non-drinkers were greater than 1.0 (e.g. 1.61 for DSM-IV obsessive–compulsive disorder and 1.67 for ICD-10 neurasthenia) but not significantly so. 4. Discussion
3.4. Psychiatric disorders and alcohol consumption 4.1. Summary of findings Table 3 shows odds ratios, with 95% confidence intervals, for broad categories of affective and anxiety disorders (DSM-IV and ICD-10 criteria) by age, sex and consumption level. These confirm higher rates of disorder in women and in younger age groups. With regard to alcohol consumption, only the odds ratios for those drinking at hazardous/harmful levels were significantly different from light drinkers, with between double and three times the likelihood of diagnosed disorder. There were trends towards non-/occasional drinkers and moderate drinkers having greater risk of diagnosed disorder, but the indicated odds ratios (range 1.15 to 1.39) were not significant at the 0.05 level. Table 4 shows odds ratios from multiple logistic regression analyses for specific DSM-IV and ICD-10 diagnoses with light drinkers as the reference category. Most odds ratios for the hazardous/harmful category were significantly greater than 1.0, with trends in the same direction when not significant. For the non-/occasional drinkers, odds ratios were only significantly elevated for dysthymia (both DSM-IV and ICD-10 diagnoses), agoraphobia (ICD-10 only), and posttraumatic stress disorder (DSM-IVonly). Some other odds ratios for the occasional/
The findings from this large nationally representative sample confirmed previous results showing Jshaped and U-shaped relationships between psychological distress and alcohol consumption levels (Power et al., 1998; Rodgers et al., 2000; Caldwell et al., 2002). Hazardous/harmful drinkers (over 40 g alcohol per day for men and 20 g per day for women) had the greatest likelihood of high distress scores on the K10 scale. Non-drinkers and occasional drinkers (less than 12 drinks in the past year) also had higher distress levels compared to light drinkers (less than 20 g alcohol per day for men and 10 g per day for women). The risk of high distress was not as great for non-/occasional drinkers as it was for the hazardous/harmful drinkers. Using the example of distress scores falling into the top 2.5% for the population (K10 score of 20 or more), odds ratios were 2.00 for non-/occasional drinkers and 3.44 for hazardous/harmful drinkers, indicating a Jshaped relationship. Findings for disorders by DSM-IVand ICD-10 criteria provided clear results only in hazardous/harmful drinkers, with consistently elevated odds ratios for any affective
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disorder, any anxiety disorder, and for more specific diagnoses, confirming our expectations from many previous studies (Regier et al., 1990; Dick et al., 1994; Grant and Harford, 1995; Kessler et al., 1996; Swendsen et al., 1998; Degenhardt et al., 2001). By contrast, odds ratios for non-/occasional drinkers were significantly greater than 1.0 only for dysthymia (ICD-10 and DSM-IV diagnoses), agoraphobia (ICD-10 only), and posttraumatic stress disorder (DSM-IV only). J-shaped relationships were less evident for diagnosed disorders than for high distress scores. However, the present study did not find any increased risk for disorder in light or moderate drinkers, compared with abstainers, as reported by Sareen et al. (2004) for major depression. 4.2. Limitations Could differences in findings relating to psychological distress on the one hand, and to diagnosed disorders on the other, be due to methodological limitations? One limitation is that non-significant findings for specific disorders may reflect reduced statistical power, particularly for low prevalence disorders such as obsessive–compulsive disorder. This, however, cannot account for the non-significant findings for relatively prevalent broad groupings of affective disorders and anxiety disorders when comparing between non-/occasional drinkers and light drinkers. Nor is limited statistical power evident for very high distress levels on the K10 (i.e. score greater than 25) which are found in only 1% of the sample. A significant difference between non-/occasional drinkers and light drinkers (OR 2.75) was found for these very high distress levels (Table 2). A second limitation is that alcohol consumption history was not collected. It would be desirable to investigate the role of past consumption in the relationships between mental health and alcohol use, but this offers no ready explanation as to why U- or J-shaped findings should be more prominent for distress than for diagnosed disorders. Furthermore, the common perception that current abstainers especially include a significant proportion of previous problem drinkers is not supported by reports that moderate drinkers are more likely to have been heavy drinkers in the past than are non-drinkers (Goldman and Najman, 1984; Power et al., 1998; Caldwell et al., 2002). Indeed, previous studies that have taken account of past drinking levels have failed to account for U- or J-shaped relationships (Power et al., 1998; Alati et al., 2005), and statistical adjustments for past heavy drinking have even exacerbated the heightened distress found in non-/occasional drinkers compared with light drinkers (Caldwell et al., 2002).
A third limitation is the finite validity of measures and this could apply to the K10 scale and the diagnoses from the CIDI-A. Clearly, these are not perfect measures but evidence indicates, for both the K10 (Kessler et al., 2002) and the CIDI (Wittchen, 1994; Kessler et al., 1998), that they are as good as (and most likely superior to) other instruments of their type. Most importantly, there is strong evidence supporting the relationship between the two measures, particularly the capacity of the K10 to discriminate individuals with affective and anxiety disorders (Andrews and Slade, 2001; Kessler et al., 2002, 2003; Furukawa et al., 2003). The prevalence of DSM-IV disorders (previous 12 months) has been shown to increase from 10.4% for K10 scores in the range 0 to 4, through 48.5% for scores of 10 to 14, to 94.0% for scores above 30, in the same sample as reported on here (Andrews and Slade, 2001). A general distinction between apparently transient symptoms and diagnosed disorders (Sareen et al., 2004) is not evident in this sample as a whole and our own findings demonstrate that it is not a useful distinction in the case of heavy drinkers. The idea that measures of general psychological distress are not accurate indicators of diagnosed affective and anxiety disorders cannot, therefore, be used to explain Sareen et al.'s (2004) findings of no elevated prevalence of diagnosed disorders in non-drinkers compared with moderate drinkers. A further limitation is that the sample was restricted to the residential population and excluded those living in hospitals, institutions, nursing homes, hotels and hostels and omitted the homeless. People with comorbid alcohol and other mental health problems may well be underrepresented in the sample and it is also possible that some of these missing groups are characterised by non-drinking in combination with mental health problems. These exclusions are likely to have reduced the strength of reported J-shaped relationships. 4.3. Do non-drinkers and heavy drinkers have different symptom profiles? The psychological distress found in non-/occasional drinkers most probably represents true elevation of a range of symptoms relative to light drinkers, but this symptomatology does not necessarily meet criteria for many affective and anxiety disorders. There was no significant elevation of risk for more prevalent disorders (depressive disorder, generalised anxiety disorder and panic disorder) in non-/occasional drinkers compared with light drinkers, as observed for high K10 scores. Increased risk for low prevalence disorders (e.g. obsessive–compulsive disorder) in abstainers can neither be
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confirmed nor ruled out by the present study because of power limitations. For disorders of intermediate prevalence (dysthymia, social phobia, agoraphobia, PTSD, and neurasthenia), variations in findings across different disorders and between results for the two classificatory systems could well have arisen by chance (Table 4). ORs were typically greater than 1.0 for non-/occasional drinkers (16 out of a total of 17 analyses), which does not support the idea of a dose–response relationship between prevalence of disorder and consumption level. Accepting the null hypothesis (same prevalence of disorder in non-/ occasional drinkers compared to light drinkers) on the basis of non-significant findings carries risk of Type 2 error and replication is therefore needed to provide more precise estimates. Investigating the full constellation of symptoms reported by non-drinkers would be more informative than contrasting their diagnoses with other drinking groups. Unfortunately, the structure of the CIDI-A in the present study precluded a comprehensive analysis of this sort, as skips are utilised throughout the interview and most respondents are required to answer only a minority of questions. 4.4. Possible explanations for increased distress and disorder in abstainers Setting aside differences in findings between measures of distress and disorder, the question remains as to why abstainers might have increased prevalence of high distress and some disorders compared to light drinkers. These observations are significant in their own right, as non-drinkers constitute a larger part of the population than heavy drinkers. They may also contribute to similar documented patterns for physical health and mortality (Shaper, 1990; Marmot and Brunner, 1991; Poikolainen, 1995; Fillmore, 2000). One possible answer is that light to moderate alcohol consumption has a general protective influence on health and wellbeing. This protective effect may be attributable to social circumstances surrounding drinking as distinct from benefits of alcohol ingestion. Second, abstainers could have personal or social background characteristics, such as poorer social support, that predispose to distress and some specific disorders (Rodgers et al., 2000; Caldwell et al., 2002), and the present findings for agoraphobia may be an extreme example of this association. Longitudinal studies will be needed to determine whether such risk factors in abstainers precede increases in distress or onset of disorder. A third possibility is that chronic or recent-onset distress or disorder may lead to giving up drinking (the “sick
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quitter” hypothesis) or to not taking up drinking in the first place. One variant of this account is the discouragement of alcohol use for those prescribed certain medications. This seems unlikely to be a major factor in the present study, where J-shaped relationships were less evident for diagnoses than for distress and were more pronounced for dysthymia than depressive disorder. Practice appears variable for prescribed psychotropics, with complete abstention being indicated for some medications and, where there is discretion, with some clinicians recommending moderation of alcohol use and others recommending complete abstention. To what extent patients follow such advice is difficult to ascertain. A second variant of this account would apply to circumstances where alcohol-related life events, such as motor vehicle accidents, could lead to both onset of disorder (e.g. PTSD) and to giving up drinking. Longitudinal data will be required to examine the sick–quitter hypothesis more thoroughly, including whether use of prescribed medications or onset of specific disorders affect drinking behaviour. A fourth explanation is that onset of some disorders (e.g. PTSD) may increase the amount of alcohol consumed by those who already drink, without changing the behaviour of abstainers. This would polarize drinking levels in those with disorders, manifesting as reduced levels of distress and disorder in light and moderate drinkers. Again, longitudinal data will be required to investigate this hypothesis thoroughly. 4.5. Conclusions Although further investigation is needed of associations of distress and disorder with non-drinking, a number of conclusions can be drawn from the present study. First, we have provided confirmation, from a large nationally representative sample, of J-shaped relationships between psychological distress and alcohol consumption. Second, we have established that associations between prevalence of specific affective and anxiety disorders and current alcohol consumption do not follow dose–response relationships. Consequently, investigations in this field should consider the whole spectrum of consumption rather than focus on heavy drinkers or problem drinkers. Third, there is new evidence that non-/occasional drinkers are at increased risk for some specific disorders compared to light drinkers. Fourth, the study presents a testable hypothesis that non-/occasional drinkers not only report lower overall levels of psychological distress compared to heavy drinkers but also that their pattern of symptomatology is of a different character.
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