No abstract

More than thirty studies of the prevalence of psychiatric disorders have been reported from Western countries in the last thirty years. Significant methodological advances have occurred, including sophistication of sampling techniques, improvements in caseness definitions and identification of cases, and clear definitions and specification of rules for diagnosis. The introduction of standardized diagnostic instruments for use by trained lay interviewers is expected to facilitate studies of psychiatric epidemiology. The methods used in each of the studies are briefly described.

Twenty persons with schizophrenia were identified in a community sample of 2144 adult household residents interviewed by trained lay interviewers using the Diagnostic Interview Schedule. The hierarchy-free lifetime prevalence for a variety of psychiatric disorders is compared in those with and without schizophrenia. Those with schizophrenia were found to have increased chances of having other disorders, all except one having had at least one other disorder. Major depressive episodes, obsessive compulsive disorder, phobia, alcohol abuse/dependence and drug abuse/dependence, each occurred in over half of the schizophrenics, and panic disorder, antisocial personality, and mania were each found in one sixth to one quarter of the schizophrenics. Although current diagnostic systems generally lack an empirical basis for hierarchies, the practical significance of co-morbidity must be determined from outcome studies, familial morbid risk data and possible differential effects of treatments.

Canadian national data on psychiatric illness are combined with results from outcome studies to derive figures for the incidence, expectancy, prevalence, prevalence of marked disability, use of institutions and loss of the work force as a result of schizophrenia and affective psychoses. It is hoped that this can be of assistance in planning services and that it will stimulate more direct research into the nature and the scope of the social, psychiatric and economic impact of these illnesses.