Gender differences in premorbid cognitive performance in a national cohortof schizophrenic patients

Despite significant research, there are still inconsistent findings regardi ng gender differences in cognitive performance in individuals already diagn osed with schizophrenia; studies have found that males suffering from schiz ophrenia are more, less or equally impaired compared with females. Gender d ifferences in cognitive performance in individuals suffering from schizophr enia may be influenced by gender differences in premorbid cognitive perform ance; the very few and very small N studies published indicated that males have a poorer pre-morbid cognitive performance than females. This study exa mined the gender differences in premorbid cognition, utilizing cognitive as sessments performed on female and male adolescents before induction into mi litary service. The Israeli Draft Board Registry, which contains cognitive assessments equivalent to IQ scores on 16-18 year old Israeli adolescents, was linked with the Israeli National Psychiatric Hospitalization Case Regis try, which records all psychiatric hospitalizations in the country. Scores on premorbid cognitive performance in schizophrenia were examined in 90 fem ale-male case pairs matched for school attended as a proxy for socio-econom ic status. The mean age of first hospitalization was 20.1 +/- 1.8 years of age for males and 19.6 +/- 1.8 years of age for females. A repeated-measure s ANCOVA with age of first hospitalization and years of formal education as covariates, and controlling for gender differences in cognitive performanc e in healthy adolescents, revealed a significant difference in pre-morbid c ognitive performance between males and females on all four cognitive measur es [F(1,87)=8.07, P=0.006] with females scoring lower (worse) than males. I n this national cohort, pre-morbid cognition was poorer in female, compared with male, adolescents who will suffer from schizophrenia in the future, a result consistent with some, but not all, similar studies. These results m ay be valid only for patients with first hospitalization around age 20. Hen ce, gender differences in premorbid cognition should be taken into account when assessing gender differences in cognition in schizophrenia. (C) 2000 E lsevier Science B.V. All rights reserved.