The epidemiology of comorbidity between alcohol use disorders and mental disorders in Australia

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Author: Lucy Burns, Maree Teesson, Michael Lynskey

Resource Type: Technical Reports

NDARC Technical Report No. 118 (2001)

EXECUTIVE SUMMARY

Aims of the report

  • This technical report examines the relationship between alcohol use disorders (a DSM-IV diagnosis of either alcohol abuse or dependence) and other mental disorders in the Australian population.
  • Specifically, this report has three main aims. The first aim is to report the prevalence of comorbidity between alcohol use disorders and other mental disorders (anxiety, affective and drug use disorders) in the Australian general population. The second aim is to examine the correlates of such comorbidity. The third aim is to examine the factor structure of alcohol dependence in those with and without a comorbid mental disorder.
     

Method

  • This report uses data from the National Survey of Mental Health and Well Being (NSMH&WB). The NSMH&WB was undertaken in 1997 on a representative sample of 10,641 Australians aged 18 years and over (a response rate of 78%). The main objectives of the NSMH&WB were to provide information on the prevalence of the most common mental disorders, the level of disability associated with these disorders, and the health services used and help needed as a consequence of these disorders. Details of the NSMH&WB are presented elsewhere (Andrews et al., 2000).


Prevalence of comorbidity : Alcohol use disorders and mental disorders

  • Approximately one-third of respondents with an alcohol use disorder (i.e. DSM-IV alcohol abuse or dependence) met criteria for at least one comorbid anxiety, affective or drug use disorder in the past 12 months.
  • The range of comorbid mental disorders in those respondents with an alcohol use disorder and a comorbid disorder was between one and six, with over half of these respondents having just one comorbid mental disorder. Approximately one quarter of these respondents had two comorbid mental disorders and one-fifth had three or more.
  • All mental disorders were more common in respondents with an alcohol use disorder, although the strength of association differed by type of mental disorder.
  • The odds of having a drug use disorder was 10 times higher, an affective disorder 4 times higher and an anxiety disorder 3 times higher in respondents with an alcohol use disorder.
  • The strongest drug associations were with stimulants and cannabis. The strongest reliable associations with affective disorders were with depression and dysthymia. With respect to anxiety disorders, the strongest association was with post-traumatic stress disorder (PTSD), followed by panic disorder.
  • The most prevalent affective disorder was depression (17%), the most prevalent anxiety disorder was generalised anxiety disorder (7%) and the most prevalent drug use disorder was cannabis (14%). Of those individuals with a twelve-month alcohol use disorder, 18% had an affective disorder, 15% had an anxiety disorder and 17% had another drug use disorder.
  • Of those respondents with a twelve-month mental disorder, 17% of those respondents with an affective disorder, 16% of those with an anxiety disorder and 35% of those with a drug use disorder also had an alcohol use disorder. With respect to common specific disorders, 16% of respondents with depression, 24% of respondents with PTSD and 37% of those with a cannabis use disorder had an alcohol use disorder.


Correlates of comorbidity : Alcohol use disorders and mental disorders

  • To identify the correlates of alcohol related comorbidity, survey respondents were characterised into four groups;
    • “pure alcohol group”, respondents with an alcohol use disorder (i.e. DSM-IV alcohol abuse or dependence) and no comorbid mental disorder;
    • “comorbid alcohol group”, respondents with an alcohol use disorder and at least one comorbid mental disorder;
    • “other disorder group”, respondents with at least one mental disorder but no alcohol disorder;
    •   “no disorder group”, respondents with no alcohol or other mental disorders.
  • These four groups were compared on a range of variables. These were age, gender, marital status, level of education, employment status, physical health, quantity and frequency of alcohol consumption, disability, suicidal behaviour and health service utilisation.
  • Relative to respondents with no disorder, respondents in the pure and comorbid alcohol groups were more likely to be male, younger (18-29 years), not in a stable relationship and unemployed.
  • The only variable that significantly differentiated between the two alcohol groups was the number of criteria of alcohol dependence. The comorbid alcohol group were fourteen times more likely to have met five or more of the dependence criteria and, subsequently, to have a diagnosis of alcohol dependence than alcohol abuse.
  • There was only a slight difference in the quantity and frequency of alcohol consumption between those in the pure and comorbid alcohol groups. Respondents in the comorbid alcohol group drank slightly more alcohol on an average drinking occasion than did respondents in the pure alcohol group.
  • Compared to respondents in the no disorder group, those in the pure alcohol group were equally as likely to have taken at least one full or partial day out of role in the previous four weeks. The comorbid alcohol group were, however, three times as likely as the no disorder group to have taken a full or partial day out of role.
  • With respect to disability, relative to individuals in the no disorder group respondents in the pure alcohol group were twice as likely and those in the comorbid alcohol group seven times as likely to have a SF-12 mental health score of less than 50 (i.e. to be disabled).
  • Suicidal behaviour was highly elevated in the comorbid alcohol group. Relative to individuals in the no disorder group those in the pure alcohol group were twice as likely and those in the comorbid alcohol group six times as likely to have either contemplated or attempted suicide.
  • Respondents in the comorbid alcohol group were more likely to seek help for their problems. Respondents in the pure alcohol group were three times as likely and those in the comorbid alcohol group nine times as likely to have sought professional help for their mental or drug and alcohol problems in the previous twelve months than those in the no disorder group.


Factor structure of alcohol dependence : Alcohol use disorders and mental disorders

  • Overall, respondents in the comorbid alcohol group were more likely to have a greater number of symptoms of alcohol dependence than respondents in the pure alcohol group. They were significantly more likely to be positive on symptoms indicative of chronic alcohol use; spending more time in obtaining alcohol, giving up social or recreational pursuits because of alcohol and using alcohol despite the knowledge it may be doing you harm.
  • Preliminary analysis revealed that in the population of drinkers (i.e. those who had consumed more than 12 alcoholic drinks in the previous twelve months) who had a comorbid mental disorder, the dependence symptoms formed a uni-dimensional syndrome. However, in the population of drinkers without a comorbid mental disorder, the syndrome split into two discrete components. This result was also found in the population of heavy drinkers (i.e. respondents who consumed more than 6 drinks on an average drinking occasion). This finding will be explored in further work.


In sum

  • Anxiety, affective and drug use disorders are more common in respondents with alcohol use disorders. Those who were comorbid were also more likely to seek specialist treatment than those without these added disorders. Despite this increased use of services, these respondents took more days taken out of role, had increased disability and more suicidal behaviour.
  • There was little difference in the demographic profiles and drinking habits of respondents with and without comorbid mental disorders. Respondents with comorbid mental disorders did appear, however, to have a more chronic and disabling type of alcohol disorder. Results of the factor analysis of alcohol dependence suggest this by showing different factor solutions in the two groups. The next stage of this research will be to undertake further analysis of the factor structure of alcohol dependence using techniques appropriate to the analysis of the dichotomous data (Muthen, 1993; 1995).
  • To identify those most at risk of alcohol related harm future research should examine in more detail the nature of alcohol dependence in these sub-groups. Further information can assist in developing more appropriate and effective initiatives in both prevention and treatment and a subsequent reduction in the burden of illness both for the individual and for society as whole.