Are the rates of schizophrenia unusually high in Canada? A comparison of Canadian and international data

Two major risk factors for schizophrenia are present in Canada, high latitude and a large and growing immigrant population. Consequently, one would expect unusually high rates of schizophrenia and an increase in these rates over time. This systematic review tests these two hypotheses. Searches of electronic databases were performed through 2011. Out of 45 studies 12 fulfilled all the inclusion criteria. The means of Canadian and international rates were compared by one-tailed unequal variance t-test. Trends with time in Canadian rates were tested by the Spearman rank correlation coefficient. Prevalence and incidence rates in Canada were significantly higher than those in international studies. Rates increased over time, with a significant increase for prevalence and a trend for incidence. This rise was supported by historical data, recent hospital admission data, and the only Canadian cohort study. The findings of elevated rates in Canada and their increase over time give concern due to the serious personal, social, and financial burden of schizophrenia. These results, based on a small number of studies, warrant confirmation by specially designed studies. They could explain the discrepant results of the risk associated with immigration in Canadian studies.