A. Jablensky et Sw. Cole, IS THE EARLIER AGE AT ONSET OF SCHIZOPHRENIA IN MALES A CONFOUNDED FINDING - RESULTS FROM A CROSS-CULTURAL INVESTIGATION, British Journal of Psychiatry, 170, 1997, pp. 234-240
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.