IS THE EARLIER AGE AT ONSET OF SCHIZOPHRENIA IN MALES A CONFOUNDED FINDING - RESULTS FROM A CROSS-CULTURAL INVESTIGATION

Background The finding of an earlier age at onset of schizophrenia in males compared with females, replicated across a number of studies, ap pears to be so robust as to support hypotheses about gender difference s in the aetiology of the disorder. However, the possibility that this observed gender effect might reflect other confounding variables has not been adequately explored. Method We analysed data on 778 men and 6 53 women, in three developing countries and in seven developed countri es, who had been assessed in the WHO 10-country study of schizophrenia . We applied a generalised linear modelling strategy to estimate the u nconfounded contributions of gender, family history, premorbid persona lity and marital status to age at onset. Results The model that explai ned the highest percentage of the total variance indicated strong main effects (P<0.001) for marital status and premorbid personality, a wea k effect for family history, and an attenuated effect for gen der. Two independent verification procedures suggested an independent onset-de laying effect for marital status (married), more marked in males. Conc lusions The gender difference in the age at onset of schizophrenia is not a robust biological characteristic of the disorder. Failure to con trol for marital status and premorbid personality in male/female compa risons of age at onset may explain a large part of the differences rep orted previously.