NDARC Technical Report No. 63 (1998)
The National Survey of Mental Health and Well-Being (NSMHWB) was the first national survey of the prevalence of common mental disorders in the Australian population. The survey interviewed a representative sample of 10,600 adults (aged 18 years or older) from throughout Australia and assessed symptoms of the affective, anxiety, and substance use disorders. Disorders were defined in terms of ICD-10 and DSM-IV diagnostic criteria, but only the ICD-10 data are presented in this report. The survey also collected detailed self-report information on: physical illness, personality disorders, the disability due to mental illness, and patterns of treatment seeking.
This report summarises data on the prevalence and correlates of the ICD-10 (WHO, 1993) substance use disorders, harmful use and dependence on alcohol, and the harmful use and dependence on four classes of drug: cannabis, stimulants, sedatives, and opioids, in the adult Australian population.
In the past 12 months, 6.5% of Australians 18 years and over had an ICD-10 alcohol use disorder, and 2.2% had another drug use disorder.
More males than females had an alcohol and other drug use disorders: 9.4% of males and 3.7% of females met criteria for an alcohol use disorder, and 3.2% of males and 1.3% of females met criteria for another drug use disorder within the past 12 months.
The prevalence of substance use disorders decreased with increasing age: 10.6% of respondents aged 18-34 years met criteria for an alcohol use disorder and 4.9% met criteria for a drug use disorder. The rates of these disorders among those aged 55 years or older were 4.4% and 0.8%, respectively.
Substance use disorders were more prevalent among: the unemployed; those who had never married; and those who were Australian-born. Other drug use disorders were more prevalent among those living in capital cities.
Alcohol was the most widely used of any drug but more users of other drugs had a use disorder in the past year. Specifically, only 8.9% of those who used alcohol in the previous 12 months had an alcohol use disorder while 22.7% of those who used other drugs had another drug use disorder.
There was a moderate degree of comorbidity between substance use disorders and other common mental health problems. Just under half of females with a substance use disorder (46%) met criteria for at least one other mental disorder (anxiety or affective), and one fifth (18%) met criteria for both an affective and an anxiety disorder. A quarter (25%) of males with a substance use disorder met criteria for another mental disorder, with 10% meeting criteria for both an anxiety and an affective disorder. Just over a third (39%) of individuals with substance use disorders had a comorbid physical disorder.
Substance use disorders were associated with a moderate degree of disability. Individuals who met criteria for a substance use disorder had a higher mean number of days out of role than those who did not meet criteria for a substance use disorder. Relatively few people with a substance use disorder had sought assistance with their substance use problem from a mental health professional (21% of women and 12% of men). Among those who sought help, general practitioners were the health professionals most likely to be consulted.
The results of the NSMHWB indicate that substance use disorders are relatively common among the Australian population. Their prevalence in Australia is reasonably comparable to that in surveys conducted in the United States using similar diagnostic interviews. The data from the NSMHWB provides a valuable resource for studying the prevalence of substance use disorders, their correlates, the disability that they cause, and the factors that predict who will and will not seek treatment for a substance use disorder. Subsequent reports will examine these issues.