Association of IQ scores and school achievement with suicide in a 40-year follow-up of a Swedish cohort

Objective: Few studies have investigated the association of childhood IQ and school achievement with suicide. The aim of this study was to investigate the association of childhood IQ with suicide in a cohort of Swedish women and men. Method: 21 809 subjects born in 1948 and 1953 who completed IQ and school tests at age 13 years have been followed until 2003. Information on paternal education and in-patient care for psychosis was linked using the Swedish personal identification number. Results: There were 180 suicides amongst subjects with measured IQ. High IQ was associated with reduced suicide risk among men (OR per unit increase in age-adjusted model 0.90, 95% CI 0.83-0.99), while there was no statistical evidence of an association in women (OR 1.04, 95% CI 0.90-1.20). Among men with a history of psychosis, high IQ was associated with an increased risk of suicide. Conclusion: Low childhood IQ at age 13 years is associated with an increased risk of suicide in men but not in women; however, amongst those with psychosis, low IQ appears to be protective.