OBJECTIVE: This study was undertaken to determine whether the incidence
of schizophrenia is equivalent for males and females. METHOD: An attempt
was made to identify every first-episode case of psychosis in a large
Canadian city over a period of 2 1/2 years. A comprehensive referral
network was established that included hospital and community settings where
psychotic persons might appear. More than 300 potential subjects were
identified, 175 of whom underwent a structured psychiatric interview and
were assigned diagnoses according to five different diagnostic systems.
RESULTS: The incidence of schizophrenia was two to three times higher among
males than among females. Even though the use of different diagnostic
systems yielded slightly different risk rates, the elevated risk for males
remained consistent. There were no differences between the sexes in the
incidence of affective psychosis. In comparison with schizophrenia, the
incidence rates for mood disorders with psychotic features were sometimes
lower and sometimes higher, depending on the diagnostic system used.
CONCLUSIONS: The findings, coupled with reports in the past 10 years from
other investigators, challenge the conventional belief that the incidence
of schizophrenia is the same for the two sexes.