Objective: To examine changes in prevalence rates of treated schizophrenia over 10 years in a small urban teaching centre using data from the Kingston Psychiatric Record Linkage System (KPRLS).
Method: The KPRLS, a psychiatric case register established in 1984, collects and links demographic, diagnostic, and service use information for all psychiatric inpatients, outpatients and emergency contacts at the 3 hospitals in Kingston, Ontario. A preliminary comparison of first admissions for schizophrenia used chart review (1976-1978) and KPRLS data (1996-1998). The KPRLS data were used to calculate population-based prevalence rates of treated schizophrenia in 3 census years (1986, 1991, 1996) for patients in the 2 counties closest to Kingston.
Results: The preliminary comparison showed a 42% decrease in the number of first-admission schizophrenia cases over 20 years. In the main study, the annual inpatient prevalence rates decreased significantly (52%) from 1986 to 1996 with no corresponding change in outpatient rates, regardless of sex. Although total major affective disorders increased, this was due to an increase in major depression, not bipolar disorder.
Conclusions: This is the first Canadian case-register study to support the widely reported falling rates of schizophrenia in other parts of the world over the last 40 years. Since this is a geographically limited prevalence study based on only 10 years of data, further research over longer periods of time in other regions of the country is required to support or refute these findings.