OBJECTIVE:

To examine changes in the prevalence of affective disorders and psychological distress among smokers and people with cannabis dependence between 1997 and 2007.

DESIGN, PARTICIPANTS AND SETTING:

Cross-sectional analysis of the 1997 and 2007 National Survey of Mental Health and Wellbeing.

MAIN OUTCOME MEASURES:

The Composite International Diagnostic Interview generated diagnoses of cannabis dependence and affective disorders based on criteria of the Diagnostic and statistical manual of mental disorders, fourth edition. Psychological distress was measured using the Kessler Psychological Distress Scale. Logistic regressions examined the relationship between affective disorders, psychological distress and (i) smoking status (current, former and never-smoker) and (ii) cannabis dependence.

RESULTS:

Affective disorders and psychological distress were more common among smokers than non-smokers and among cannabis-dependent participants in both years. The prevalence of affective disorders and psychological distress among smokers, ex-smokers and non-smokers did not change between 1997 and 2007. Psychological distress and affective disorders were more common in cannabis-dependent participants in 2007 than in 1997.

CONCLUSION:

Affective disorders were more common in current than never-smokers and in people with cannabis dependence than without. We did not find strong evidence that the prevalence of these disorders changed in smokers between 1997 and 2007, but we did find such evidence in cannabis-dependent people.