Sex difference in age at onset of schizophrenia: discrepant findings from India.

Consecutive male (n=100) and female (n=100) DSM-IV schizophrenics newly registered for treatment in a large psychiatric hospital were examined with regard to age at onset of the first psychotic symptom. Age at onset of the first psychotic symptom did not differ between the sexes regardless of whether schizophrenia was diagnosed by DSM-IV or by several alternative systems. Age at onset defined by other criteria, namely age at first contact with a physician, and age at first admission for psychiatric care, also did not show any differences between the sexes. Survival analysis of subjects having a documented date of birth revealed a female preponderance at younger ages. A higher positive symptom score predicted older age at onset of the first psychotic symptom in the total sample. These findings call into question the universality of the traditional view of a younger age at onset of schizophrenia among males. Tentative neurodevelopmental and cultural explanations are presented to explain why there is no sex difference in age at onset of schizophrenia in India.