Prevalence of co-occurring substance use and other mental disorders in the Canadian population

Population health surveys around the world have studied the epidemiology of comorbid substance use disorders (SUDs) and other mental disorders as part of larger efforts to assess needs and direct integrated planning and delivery of services. This study presents the first national assessment in Canada of the prevalence of co-occurring SUDs and other mental disorders, with attention to differences by substance problem severity, sex, age, and region.

This work is a secondary analysis of data from the 2002 Canadian Community Health Survey: Mental Health and Well-Being. The sample was obtained using a multistage stratified cluster design (n = 36,984, response rate = 77%).

The 12-month population prevalence of co-occurring disorders was 1.7%. The 12-month prevalence of other mental disorders was higher among those with illicit drug, relative to alcohol, problems and among those with dependence, compared with those with less severe problems. Sex and age differences mirrored population differences in pure disorders. Salient regional differences included the higher rate of co-occurring disorders in British Columbia and the lower rates in Quebec.

Cross-study comparisons are hampered by methodological differences; however, these Canadian rates are at the lower end of the range reported internationally. This might have resulted from the exclusion of several disorders known to be highly comorbid with SUDs. Nonetheless, prevalence is high in certain subgroups, and efforts under way to improve Canada's substance abuse and mental health services should continue to ensure that adequate attention is directed to the needs of people with co-occurring disorders.