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.

AIM: To compare relationships between alcohol, cannabis and tobacco and indicators of mental health problems in the general population.
METHOD: A survey of a nationally representative sample of 10 641 Australian adults (the National Survey of Mental Health and Well-Being (NSMHWB)) provided data on alcohol, cannabis and tobacco use and mental health (DSM-IV anxiety disorders, affective disorders, other substance use disorders and screening positively for psychosis).
FINDINGS: Alcohol showed a "J-shaped" relationship with DSM-IV affective and anxiety disorders: alcohol users had lower rates of these problems than non-users of alcohol, while those meeting criteria for alcohol dependence had the highest rates. Tobacco and cannabis use were both associated with increased rates of all mental health problems examined. However, after controlling for demographics, neuroticism and other drug use, cannabis was not associated with anxiety or affective disorders. Alcohol dependence and tobacco use remained associated with both of these indicators of mental health. All three types of drug use were associated with higher rates of other substance use problems, with cannabis having the strongest association.
CONCLUSIONS: The use of alcohol, tobacco and cannabis are associated with different patterns of co-morbidity in the general population.