Background: Schizophrenia first appears in adolescence, in boys at an earlier age than girls. The interpretation of this key epidemiological finding crucially depends on whether similar age-related sex differences exist in the expression of associated, subclinical psychosis-like experiences. Methods: Findings are based on a population sample of 2548 adolescents and young adults aged 17–28. Subjects were assessed with the core psychosis sections on delusions and hallucinations of the Munich- Composite International Diagnostic Interview. Results: The risk of subclinical psychotic experiences was significantly higher for males in the younger half of the cohort (17–21 years), but similar in the older half (22–28 years). Conclusions: These findings suggest that normal maturational changes in adolescence with differential age of onset in boys and girls cause the expression of psychosis, the extreme of which is schizophrenia.

Background: Schizophrenia first appears in adolescence, in boys at an earlier age than girls. The interpretation of this key epidemiological finding crucially depends on whether similar age-related sex differences exist in the expression of associated, subclinical psychosis-like experiences. Methods: Findings are based on a population sample of 2548 adolescents and young adults aged 17–28. Subjects were assessed with the core psychosis sections on delusions and hallucinations of the Munich- Composite International Diagnostic Interview. Results: The risk of subclinical psychotic experiences was significantly higher for males in the younger half of the cohort (17–21 years), but similar in the older half (22–28 years). Conclusions: These findings suggest that normal maturational changes in adolescence with differential age of onset in boys and girls cause the expression of psychosis, the extreme of which is schizophrenia.