Premorbid personality factors in schizophrenia and bipolar disorder: results from a large cohort study of male conscripts.

The present study explored the premorbid personality traits Neuroticism, Extraversion, and Disinhibition in individuals later diagnosed with psychotic disorders. Results on personality questionnaires and intellectual performance tests were obtained for 213,443 apparently healthy male subjects (mean age: 20.1 years) conscripted into the Finnish Defence Forces during the period 1982-1987. Linkage with the Finnish Hospital Discharge Register (mean follow-up time: 14.1 years, SD = 1.7) identified conscripts later diagnosed with schizophrenia (N = 1,328), bipolar disorder (N = 98), or other psychoses (N = 456). Both before and after controlling for intellectual performance, high Neuroticism predicted future onset of schizophrenia and other psychoses, and high Extraversion predicted future onset of bipolar disorder. The data of the present research showed for the 1st time that premorbid personality traits predict heightened risk for psychotic disorders beyond intellectual performance and also showed for the 1st time an association between premorbid Extraversion and bipolar disorder.