Journal of Affective Disorders 99 (2007) 165–172www.elsevier.com/locate/jad

Research report

Affective disorders, anxiety disorders and psychologicaldistress 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, Australiab 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 2006Available online 12 October 2006

Abstract

Background: Non-drinkers have elevated levels of psychological distress but a recent study reported no elevation in prevalence ofdiagnosed disorders. We aimed to determine the prevalence of affective and anxiety disorders (from the CIDI-A) in currentabstainers 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 waseven higher. Heavy drinkers also had the highest rates of most disorders. Non-/occasional drinkers showed significantly elevatedprevalence 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 notcollected. The CIDI-A and K10 have finite validity.Conclusions: This study confirmed J-shaped relationships between psychological distress and alcohol consumption. Althoughaffective and anxiety disorders also showed non-linear relationships with alcohol consumption, non-/occasional drinkers are not atincreased risk for all disorders compared to light drinkers. The pattern of symptomatology in non-/occasional drinkers may be of adifferent 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 ofaffective and anxiety disorders in people with alcohol usedisorders (Regier et al., 1990; Dick et al., 1994; Grant andHarford, 1995; Kessler et al., 1996; Swendsen et al., 1998;Degenhardt et al., 2001), less is known about the mentalhealth of non-drinkers. Some recent studies have found

⁎ Corresponding author. Tel.: +61 2 6125 0399; fax: +61 2 6125 0740.E-mail address: Bryan.Rodgers@anu.edu.au (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 non-drinkers than light or moderate drinkers (Power et al.,1998; Rodgers et al., 2000; Caldwell et al., 2002; Alatiet al., 2005). However, a report based on two generalpopulation surveys of mental disorders found “noevidence of a U-shaped relationship between lifetimealcohol consumption and lifetime mood and anxietydisorders” (Sareen et al., 2004). Indeed, a greater lifetimeprevalence ofmajor depressionwas reported for moderatedrinkers than for lifetime abstainers. The authors em-phasised the distinction between transient mood and

166 B. Rodgers et al. / Journal of Affective Disorders 99 (2007) 165–172

anxiety symptoms that are not necessarily indicative ofpathology or psychiatric disorders as determined by reli-ably structured diagnostic interviews.

A difficulty with this account is that symptom mea-sures, including those used in the aforementioned studies,demonstrate substantial temporal stability and gooddiscrimination of individuals with recognised clinicaldisorders (Rodgers et al., 1999). The present studytherefore aimed to investigate the prevalence of affectiveand anxiety disorders in abstainers compared with lightdrinkers and to compare these results directly with find-ings for psychological distress in the same sample. Dis-orders were identified by a structured diagnostic interviewand symptoms assessed by a scale known to discriminateindividuals with these disorders. This was feasible using alarge survey of mental disorders in the Australian adultpopulation; the Australian National Survey of MentalHealth and Wellbeing.

2. Methods

The fieldwork for the National Survey of MentalHealth and Wellbeing was conducted by the AustralianBureau of Statistics in 1997 (Australian Bureau ofStatistics, 1998).

2.1. Sample

The target population was adult residents of privatedwellings living in all States and Territories of Australia.The sample excluded people living in special dwellings,such as hospitals, institutions, nursing homes, hotels andhostels and also excluded some private dwellings inremote and sparsely populated areas. Overseas visitors,members of non-Australian defence forces and non-Australian diplomatic personnel were also excluded. Thesample was otherwise representative of the resident adultpopulation. In all, 13,624 dwellings were sampled. Oneperson aged 18 years or over was randomly selected fromeach dwelling to participate in the survey. Participationwas voluntary. The achieved sample was 10,641, repre-senting a 78% response rate.Weights for each recordwerederived using the jackknifemethod of replicateweighting.

2.2. Data collection and measures

Information was gathered by computer-assisted per-sonal interviewing. As well as information on demograph-ic and other social characteristics, the main instrument fordata collection was the automated version of the Com-posite International Diagnostic Interview (CIDI-A; WorldHealth Organization, 1997). Measures of psychological

distress were also obtained during the interview, includingthe Kessler 10-item psychological distress scale (K10;Andrews and Slade, 2001; Kessler et al., 2002). Onlyfindings based on the K10 scale are reported in this paper,as this has been found to be the measure of distress bestpredictive of psychiatric diagnoses (Furukawa et al.,2003), but similar results were found for the 12-itemversion of the General Health Questionnaire (GHQ-12;Goldberg andWilliams, 1988) and the mental health scaleof the Short Form 12 (SF-12) derived from the MedicalOutcomes Study (Ware et al., 1996). In this report, totalscores from the K10 are expressed on a scale from 0 to 40,reflecting ratings of the experience of individual symp-toms ranging from 0 (none of the time in the past fourweeks) to 4 (all of the time in the past 4 weeks).

2.3. Alcohol consumption

The alcohol-related disorders module of the CIDI-Abegins with the stem question “In the past 12 months,have you had at least 12 drinks of any kind of alcoholicbeverage?” This is followed by a second confirmatoryquestion specifically stating that drinking on special oc-casions or holidays should be included. For those whorespond affirmatively, follow-up questions are asked onthe typical frequency of drinking over the past 12 monthsand the typical amount consumed on drinking days,expressed in terms of the number of drinks. The definitionof a standard drink in Australia is one containing 10 g or12.5 ml of ethanol and the number of standard drinkscontained in packaged beverages is displayed on bottles,cans and cartons. Familiarity with this labelling is en-hanced by references in educational information to per-mitted alcohol levels for driving. For the present study, anestimate of average weekly consumption was constructedfrom the CIDI responses, following conventional proce-dures for quantity–frequency assessment (Shakeshaftet al., 1999). Individuals were classified into four cate-gories of (1) non-drinkers and occasional drinkers (lessthan 12 drinks in the past year), (2) light drinkers (up to 14standard drinks per week for men and 7 per week forwomen), (3) moderate drinkers (up to 28 standard drinksper week for men and 14 per week for women), and (4)those drinking at hazardous or harmful levels (over 28 and14 standard drinks per week respectively) as defined bythe National Health and Medical Research Council ofAustralia (National Health and Medical Research Coun-cil, 2001). Although there is a consensus that the sameconsumption levels have different consequences for menand women (Graham et al., 1998), doubt remains as to thedegree of difference. All analyses in the present study,therefore, used sex as a covariate and included the testing

167B. Rodgers et al. / Journal of Affective Disorders 99 (2007) 165–172

of statistical interactions between sex and other indepen-dent variables (i.e. age and consumption level).

2.4. Classification of psychiatric disorders

Psychiatric disorders were classified by both DSM-IVand ICD-10 criteria. Variables representing prevalentdisorders (past 12 months) were obtained from com-puter algorithms applied to the original symptom datacollected at interview. The disorders covered by theinterview included mood disorders (major depressivedisorder, dysthymic disorder and mania) and anxietydisorders (social phobia, agoraphobia, panic disorder,generalised anxiety disorder, obsessive–compulsive dis-order, and posttraumatic stress disorder). An additionalmodule covering neurasthenia (ICD-10 diagnosis) wasincluded in the interview (Hickie et al., 2002).

2.5. Statistical analysis

Initial data analysis employed the negative binomialmodel to identify factors associated with continuousoutcome measures that have markedly skewed distribu-tions (e.g. the K10). In this model, the coefficient cderived for a predictor variable is more easily interpretedas an incidence rate ratio (IRR) ec that measures theexpected change in the dependent variable as a result ofone unit change in the predictor variable. Binary logisticregression analyses were used for dichotomous outcomemeasures (such as CIDI-A diagnoses of mentaldisorders). Multivariate models included the assessmentof interaction terms between independent variables andthese were omitted progressively from the models when

Table 1Alcohol consumption level (%), mean K10 score, and prevalence of 12-mongroup

Males

18–29 30–39 40–49 50–59 60–6

Number 874 1057 986 699 553Weighted N (‘000s) 159.97 138.99 128.56 96.57 66.Alcohol consumption (%)

Non-/occasional 15.2 16.5 15.0 16.1 19.Light 68.0 65.5 65.6 62.3 58.Moderate 11.5 11.7 12.2 11.7 14.Hazardous/harmful 5.2 6.3 7.2 9.9 8.

K10 scoreMean 5.1 5.1 5.1 4.7 4.SD 4.4 4.7 5.4 5.4 5.

DSM-IV affective disorders (%) 4.7 6.6 5.6 6.0 2.DSM-IV anxiety disorders (%) 4.5 5.3 5.8 4.7 2.ICD 10 affective disorders (%) 4.4 7.8 6.2 6.3 3.ICD 10 anxiety disorders (%) 8.0 7.9 9.3 8.0 4.

found to be non-significant. Paired contrasts were ap-plied to final models using light drinking groups asreference categories.

Analyses were carried out using SPSS 11.5 andSTATA 7.0. The latter allowed use of jackknife weightsprovided with the data to obtain survey estimates con-forming to independent estimation of the Australianpopulation at the time of the survey.

3. Results

3.1. Alcohol consumption levels

The proportion of individuals falling into the fourdefined levels of alcohol consumption is shown for eachage 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). Formost age groups, the rate of non-/occasional drinking inwomen is at least double that seen for men. Correspond-ingly, rates of hazardous and harmful drinking are greaterin men than women, though this was least evident in the18–29 age group. The greatest prevalence of hazardous/harmful consumption was seen in men aged 50–59(9.9%). Forwomen, the highest ratewas in the 60–69 yeargroup (6.5%). For all age groups, in bothmen andwomen,light drinkingwasmore prevalent thanmoderate drinking.

3.2. Psychological distress and prevalence of disorders

Table 1 also shows mean K10 scores by age group andsex and the 12-month prevalence of broad categories of

th DSM-IV and ICD-10 affective and anxiety disorders by sex and age

Females

9 70 andover

18–29 30–39 40–49 50–59 60–69 70 andover

442 1181 1341 1127 816 605 75478 59.54 157.04 141.50 130.23 94.73 68.61 78.98

0 30.3 26.1 32.5 35.1 39.3 49.8 61.44 57.9 60.7 55.8 51.4 46.0 34.9 30.13 8.3 8.5 8.4 8.5 9.4 8.8 6.73 3.6 4.7 3.4 5.0 5.4 6.5 1.7

4 4.9 6.1 5.8 5.7 5.5 4.3 4.32 4.7 5.4 5.6 5.6 5.9 4.5 4.37 1.0 10.1 9.7 9.3 9.6 5.7 2.30 1.8 8.5 9.2 6.8 7.1 3.2 1.62 1.5 11.5 10.2 10.3 10.1 6.8 2.37 7.5 13.9 15.3 16.3 15.0 11.0 4.2

Table 2Binomial regression model and logistic regression models of K10 scores by sex, age group and consumption level

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)

Predictor variablesSexFemale 1.10 (1.01–1.21) 1.22 (0.97–1.53) 1.12 (0.78–1.59) 1.44 (0.92–2.28)

Age groupa

18–29 1.33 (1.22–1.45) 1.75 (1.34–2.27) 1.04 (0.43–2.49) 1.46 (0.31–6.74)30–39 1.28 (1.18–1.39) 1.73 (1.35–2.21) 1.48 (0.71–3.09) 2.91 (0.67–12.61)40–49 1.25 (1.12–1.41) 1.72 (1.20–2.47) 2.29 (1.15–4.55) 3.17 (0.62–16.15)50–59 1.18 (1.07–1.30) 1.57 (1.13–2.18) 2.29 (0.99–5.33) 3.90 (0.77–19.71)60–69 1.00 (0.90–1.11) 1.10 (0.80–1.50) 1.17 (0.49–2.77) 1.68 (0.33–8.63)

Alcohol consumptionb

Non-drinkers 1.13 (1.05–1.22) 1.43 (1.19–1.72) 2.00 (1.40–2.85) 2.75 (1.37–5.53)Moderate 1.10 (1.02–1.18) 1.26 (1.03–1.55) 1.45 (0.60–3.51) 1.98 (0.61–6.43)Hazardous/harmful 1.36 (1.21–1.52) 2.14 (1.52–3.02) 3.44 (2.19–5.41) 7.13 (3.49–14.60)

aCompared with those aged 70 and over.bCompared with light drinkers.

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affective disorders and anxiety disorders. Psychologicaldistress scores were highest in the youngest age groupsand, except for those aged 60 or more, were higher inwomen thanmen. For diagnosed disorders, the prevalenceof affective disorders and anxiety disorders was relativelylow in those aged 60 or more, but there was not such aclear trend across the younger age groups. The prevalenceof both affective and anxiety disorders was higher inwomen than men (as expected) across age groups, withthe exception of anxiety disorders in those aged 70 yearsand over.

3.3. Psychological distress and alcohol consumption

The first column of Table 2 shows IRRs from thenegative binomial regression analysis of K10 psycholog-

Table 3Logistic regression models of DSM-IV and ICD-10 affective and anxiety di

DSM-IV affective disorders DSM-IV anxiety d

Odds ratio (95% CI) Odds ratio (95%

Predictor variablesSexFemale 1.82 (1.47–2.27) 1.59 (1.13–2.22)

Age groupa

18–29 4.88 (2.82–8.46) 4.48 (2.31–8.69)30–39 5.37 (2.84–10.18) 5.02 (2.96–8.50)40–49 4.76 (2.60–8.72) 4.19 (2.02–8.70)50–59 4.93 (2.81–8.66) 3.79 (2.22–6.49)60–69 2.50 (1.03–6.09) 1.59 (0.84–3.01)

Alcohol consumptionb

Non-drinkers 1.28 (0.90–1.82) 1.39 (0.95–2.01)Moderate 1.30 (0.89–1.90)) 1.23 (0.71–2.14)Hazardous/harmful 2.62 (1.93–3.54) 2.90 (1.97–4.27)

aCompared with those aged 70 and over.bCompared with light drinkers.

ical distress scores by sex, age group and level of alcoholconsumption. All three independent variables were sig-nificantly and independently associated with K10 scores,with no significant interactions. IRR for sex reflectshigher distress in women, and IRRs for age group(70 years and over group as comparison) show higherdistress in younger age groups (except 60–69 years) withdifferences increasing with decreasing age. For alcoholconsumption, all other groups showed higher distress thanlight drinkers with the greatest distress evident in haz-ardous/harmful drinkers.

This pattern is further illustrated in the second, thirdand fourth columns of Table 2 where odds ratios (fromlogistic regressions) are reported for high K10 scoresusing cut-points of 10 or more, 20 or more and 25 ormore (i.e. approximating the top 10%, 2.5% and 1% of

sorders by sex, age group and consumption level

isorders ICD-10 affective disorders ICD-10 anxiety disorders

CI) Odds ratio (95% CI) Odds ratio (95% CI)

1.84 (1.43–2.38) 1.96 (1.47–2.60)

4.75 (2.58–8.75) 2.99 (2.02–4.45)5.41 (2.55–11.45) 3.20 (2.18–4.69)4.81 (2.42–9.54) 3.56 (2.13–5.94)4.66 (2.33–9.35) 3.08 (1.86–5.11)2.69 (1.17–6.17) 1.98 (1.25–3.14)

1.28 (0.87–1.88) 1.15 (0.88–1.50)1.26 (0.87–1.82) 1.24 (0.95–1.61)2.58 (1.99–3.35) 2.05 (1.53–2.75)

Table 4Odds ratios for consumption level a from multiple logistic regression models for specific DSM-IV and ICD-10 disorders

Depression Dysthymia SocialPhobia

Agoraphobia Panicdisorder

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)

DSM-IV diagnoses

Non-drinkers1.23 2.86 1.77 1.30 1.06 1.18 1.61 2.17 n.a.(0.91–1.66) (1.47–5.56) (0.84–3.73) (0.48–3.47) (0.61–1.85) (0.69–2.03) (0.93–2.80) (1.22–3.87)

Moderate 1.29 2.06 0.98 0.90 1.10 1.59 0.82 1.31 n.a.(0.85–1.96) (0.58–7.31) (0.25–3.93) (0.19–4.19) (0.48–2.53) (0.76–3.32) (0.16–4.26) (0.64–2.67)

Hazardous/harmful

2.57 5.63 2.31 3.32 3.61 2.70 1.66 4.87 n.a.(2.02–3.26) (2.95–10.74) (1.32–4.03) (0.58–18.91) (1.51–8.62) (1.56–4.69) (0.43–6.44) (3.20–7.40)

ICD-10 diagnosesNon-drinkers 1.23 2.29 1.09 1.94 0.98 1.18 1.72 1.50 1.67

(0.89–1.71) (1.12–4.66) (0.74–1.61) (1.03–3.66) (0.63–1.54) (0.89–1.56) (0.78–3.79) (0.88–2.54) (0.83–3.39)Moderate 1.27 1.50 1.31 1.80 1.14 1.25 1.02 0.88 0.97

(0.82–1.97) (0.50–4.55) (0.71–2.41) (0.63–5.18) (0.61–2.13) (0.81–1.95) (0.06–17.07) (0.51–1.51) (0.45–2.09)Hazardous/harmful

2.54 4.14 1.36 4.34 1.14 2.36 3.01 2.41 1.99(1.98–3.26) (2.21–7.75) (0.72–2.57) (1.93–9.76) (0.62–2.09) (1.45–3.83) (0.68–13.43) (1.41–4.14) (1.13–3.52)

a Compared with light drinkers.

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scores respectively). Odds ratios are significantlygreater than 1.0 for both non-/occasional drinkers andhazardous/harmful drinkers relative to light drinkers,across all three cut-points.

3.4. Psychiatric disorders and alcohol consumption

Table 3 shows odds ratios, with 95% confidenceintervals, for broad categories of affective and anxietydisorders (DSM-IV and ICD-10 criteria) by age, sex andconsumption level. These confirm higher rates of disorderin women and in younger age groups. With regard toalcohol consumption, only the odds ratios for thosedrinking at hazardous/harmful levels were significantlydifferent from light drinkers, with between double andthree times the likelihood of diagnosed disorder. Therewere trends towards non-/occasional drinkers and mod-erate drinkers having greater risk of diagnosed disorder,but the indicated odds ratios (range 1.15 to 1.39) were notsignificant at the 0.05 level.

Table 4 shows odds ratios from multiple logistic reg-ression analyses for specific DSM-IV and ICD-10 diag-noses with light drinkers as the reference category. Mostodds ratios for the hazardous/harmful category were sig-nificantly greater than 1.0, with trends in the samedirection when not significant. For the non-/occasionaldrinkers, odds ratios were only significantly elevated fordysthymia (both DSM-IV and ICD-10 diagnoses), ago-raphobia (ICD-10 only), and posttraumatic stress disorder(DSM-IVonly). Some other odds ratios for the occasional/

non-drinkers were greater than 1.0 (e.g. 1.61 for DSM-IVobsessive–compulsive disorder and 1.67 for ICD-10neurasthenia) but not significantly so.

4. Discussion

4.1. Summary of findings

The findings from this large nationally representa-tive sample confirmed previous results showing J-shaped and U-shaped relationships between psycho-logical distress and alcohol consumption levels (Poweret al., 1998; Rodgers et al., 2000; Caldwell et al., 2002).Hazardous/harmful drinkers (over 40 g alcohol per dayfor men and 20 g per day for women) had the greatestlikelihood of high distress scores on the K10 scale.Non-drinkers and occasional drinkers (less than 12drinks in the past year) also had higher distress levelscompared to light drinkers (less than 20 g alcohol perday for men and 10 g per day for women). The risk ofhigh distress was not as great for non-/occasionaldrinkers as it was for the hazardous/harmful drinkers.Using the example of distress scores falling into the top2.5% for the population (K10 score of 20 or more),odds ratios were 2.00 for non-/occasional drinkers and3.44 for hazardous/harmful drinkers, indicating a J-shaped relationship.

Findings for disorders by DSM-IVand ICD-10 criteriaprovided 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 specificdiagnoses, confirming our expectations from many pre-vious studies (Regier et al., 1990; Dick et al., 1994; Grantand Harford, 1995; Kessler et al., 1996; Swendsen et al.,1998; Degenhardt et al., 2001). By contrast, odds ratiosfor non-/occasional drinkers were significantly greaterthan 1.0 only for dysthymia (ICD-10 and DSM-IV diag-noses), agoraphobia (ICD-10 only), and posttraumaticstress disorder (DSM-IV only). J-shaped relationshipswere less evident for diagnosed disorders than for highdistress scores. However, the present study did not findany increased risk for disorder in light or moderate drink-ers, compared with abstainers, as reported by Sareen et al.(2004) for major depression.

4.2. Limitations

Could differences in findings relating to psychologicaldistress on the one hand, and to diagnosed disorders on theother, be due to methodological limitations? One limit-ation is that non-significant findings for specific disordersmay reflect reduced statistical power, particularly for lowprevalence disorders such as obsessive–compulsive dis-order. This, however, cannot account for the non-sig-nificant findings for relatively prevalent broad groupingsof affective disorders and anxiety disorders when com-paring between non-/occasional drinkers and lightdrinkers. Nor is limited statistical power evident forvery high distress levels on the K10 (i.e. score greater than25) which are found in only 1% of the sample. A sig-nificant difference between non-/occasional drinkers andlight drinkers (OR 2.75) was found for these very highdistress levels (Table 2).

A second limitation is that alcohol consumption his-tory was not collected. It would be desirable to investigatethe role of past consumption in the relationships betweenmental health and alcohol use, but this offers no readyexplanation as to why U- or J-shaped findings should bemore prominent for distress than for diagnosed disorders.Furthermore, the common perception that current abstai-ners especially include a significant proportion of pre-vious problem drinkers is not supported by reports thatmoderate drinkers are more likely to have been heavydrinkers in the past than are non-drinkers (Goldman andNajman, 1984; Power et al., 1998; Caldwell et al., 2002).Indeed, previous studies that have taken account of pastdrinking levels have failed to account for U- or J-shapedrelationships (Power et al., 1998; Alati et al., 2005), andstatistical adjustments for past heavy drinking have evenexacerbated the heightened distress found in non-/oc-casional drinkers compared with light drinkers (Caldwellet al., 2002).

A third limitation is the finite validity of measures andthis could apply to the K10 scale and the diagnoses fromthe CIDI-A. Clearly, these are not perfect measures butevidence indicates, for both the K10 (Kessler et al., 2002)and the CIDI (Wittchen, 1994; Kessler et al., 1998), thatthey are as good as (and most likely superior to) otherinstruments of their type.Most importantly, there is strongevidence supporting the relationship between the twomeasures, particularly the capacity of the K10 to dis-criminate individuals with affective and anxiety disorders(Andrews and Slade, 2001; Kessler et al., 2002, 2003;Furukawa et al., 2003). The prevalence of DSM-IVdisorders (previous 12 months) has been shown toincrease 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 scoresabove 30, in the same sample as reported on here(Andrews and Slade, 2001). A general distinction bet-ween apparently transient symptoms and diagnosed dis-orders (Sareen et al., 2004) is not evident in this sample asa whole and our own findings demonstrate that it is not auseful distinction in the case of heavy drinkers. The ideathat measures of general psychological distress are notaccurate indicators of diagnosed affective and anxietydisorders cannot, therefore, be used to explain Sareenet al.'s (2004) findings of no elevated prevalence ofdiagnosed disorders in non-drinkers compared withmoderate drinkers.

A further limitation is that the sample was restrictedto the residential population and excluded those living inhospitals, institutions, nursing homes, hotels and hostelsand omitted the homeless. People with comorbid al-cohol and other mental health problems may well beunderrepresented in the sample and it is also possiblethat some of these missing groups are characterised bynon-drinking in combination with mental health pro-blems. These exclusions are likely to have reduced thestrength of reported J-shaped relationships.

4.3. Do non-drinkers and heavy drinkers have differentsymptom profiles?

The psychological distress found in non-/occasionaldrinkers most probably represents true elevation of arange of symptoms relative to light drinkers, but thissymptomatology does not necessarily meet criteria formany affective and anxiety disorders. There was nosignificant elevation of risk for more prevalent disorders(depressive disorder, generalised anxiety disorder andpanic disorder) in non-/occasional drinkers comparedwith light drinkers, as observed for high K10 scores.Increased risk for low prevalence disorders (e.g. obses-sive–compulsive disorder) in abstainers can neither be

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confirmed nor ruled out by the present study because ofpower limitations. For disorders of intermediate preva-lence (dysthymia, social phobia, agoraphobia, PTSD, andneurasthenia), variations in findings across different dis-orders and between results for the two classificatory sys-tems could well have arisen by chance (Table 4). ORswere typically greater than 1.0 for non-/occasional drink-ers (16 out of a total of 17 analyses), which does notsupport the idea of a dose–response relationship betweenprevalence of disorder and consumption level. Acceptingthe null hypothesis (same prevalence of disorder in non-/occasional drinkers compared to light drinkers) on thebasis of non-significant findings carries risk of Type 2error and replication is therefore needed to provide moreprecise estimates.

Investigating the full constellation of symptomsreported by non-drinkers would be more informativethan contrasting their diagnoses with other drinkinggroups. Unfortunately, the structure of the CIDI-A in thepresent study precluded a comprehensive analysis ofthis sort, as skips are utilised throughout the interviewand most respondents are required to answer only aminority of questions.

4.4. Possible explanations for increased distress anddisorder in abstainers

Setting aside differences in findings between mea-sures of distress and disorder, the question remains as towhy abstainers might have increased prevalence of highdistress and some disorders compared to light drinkers.These observations are significant in their own right, asnon-drinkers constitute a larger part of the populationthan heavy drinkers. They may also contribute to similardocumented patterns for physical health and mortality(Shaper, 1990; Marmot and Brunner, 1991; Poikolainen,1995; Fillmore, 2000). One possible answer is that lightto moderate alcohol consumption has a general pro-tective influence on health and wellbeing. This pro-tective effect may be attributable to social circumstancessurrounding drinking as distinct from benefits of alcoholingestion. Second, abstainers could have personal orsocial background characteristics, such as poorer socialsupport, that predispose to distress and some specificdisorders (Rodgers et al., 2000; Caldwell et al., 2002),and the present findings for agoraphobia may be anextreme example of this association. Longitudinalstudies will be needed to determine whether such riskfactors in abstainers precede increases in distress oronset of disorder.

A third possibility is that chronic or recent-onset dis-tress or disorder may lead to giving up drinking (the “sick

quitter” hypothesis) or to not taking up drinking in the firstplace. One variant of this account is the discouragement ofalcohol use for those prescribed certain medications. Thisseems unlikely to be a major factor in the present study,where J-shaped relationships were less evident for diag-noses than for distress and were more pronounced fordysthymia than depressive disorder. Practice appearsvariable for prescribed psychotropics, with completeabstention being indicated for some medications and,where there is discretion, with some clinicians recom-mending moderation of alcohol use and others recom-mending complete abstention. To what extent patientsfollow such advice is difficult to ascertain. A secondvariant of this account would apply to circumstanceswhere alcohol-related life events, such as motor vehicleaccidents, could lead to both onset of disorder (e.g. PTSD)and to giving up drinking. Longitudinal data will berequired to examine the sick–quitter hypothesis morethoroughly, including whether use of prescribed medica-tions or onset of specific disorders affect drinkingbehaviour.

A fourth explanation is that onset of some disorders(e.g. PTSD) may increase the amount of alcohol con-sumed by those who already drink, without changing thebehaviour of abstainers. This would polarize drinkinglevels in those with disorders, manifesting as reducedlevels of distress and disorder in light and moderatedrinkers. Again, longitudinal data will be required toinvestigate this hypothesis thoroughly.

4.5. Conclusions

Although further investigation is needed of associa-tions of distress and disorder with non-drinking, anumber of conclusions can be drawn from the presentstudy. First, we have provided confirmation, from a largenationally representative sample, of J-shaped relation-ships between psychological distress and alcoholconsumption. Second, we have established that associa-tions between prevalence of specific affective andanxiety disorders and current alcohol consumption donot follow dose–response relationships. Consequently,investigations in this field should consider the wholespectrum of consumption rather than focus on heavydrinkers or problem drinkers. Third, there is newevidence that non-/occasional drinkers are at increasedrisk for some specific disorders compared to lightdrinkers. Fourth, the study presents a testable hypothesisthat non-/occasional drinkers not only report loweroverall levels of psychological distress compared toheavy drinkers but also that their pattern of symptom-atology is of a different character.

172 B. Rodgers et al. / Journal of Affective Disorders 99 (2007) 165–172

Acknowledgements

This work was supported by Program Grant No.179805 from the National Health and Medical ResearchCouncil of Australia. Bryan Rodgers has been supportedby NHMRC Research Fellowships No. 148948 and No.366758. The National Drug and Alcohol Research Centreis funded by the Australian Government Department ofHealth and Ageing. The authors are grateful to the twoanonymous reviewers who provided very useful feedbackon an earlier draft of the manuscript.

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