Search for protective factors for psychosis - a population-based sample with special interest in unaffected individuals with parental psychosis.

Aim: To find factors that are associated with not having psychotic illness in a prospective general population sample, with a special interest in individuals with parental psychosis.

Methods: Data from the Northern Finland Birth Cohort 1966 (n = 10 458) and several registers were used to detect individuals with and without parental psychosis. Altogether, 594 persons had parent(s) with psychosis and 48 of them also had psychosis subsequently. Variables related to pregnancy and birth, family and childhood, health and habits in adolescence, school performance and physical activity were studied to identify determinants of unaffected status among individuals with and without parental psychosis.

Results: In the parental psychosis group, the unaffected persons had more likely a mother who was non-depressed during pregnancy, and who worked outside the home or studied than among those who developed psychosis.

Conclusions: Protective factors for psychosis were surprisingly few in this sample. These factors were related to the mother's non-depressed mood and the mother's work outside the home or studies. This could relate to better health and functioning of a mother. This work highlights the need for more research on protective factors for psychosis in order to identify methods for prevention of psychosis.