School performance and risk of suicide in early adulthood: follow-up of two national cohorts of Swedish schoolchildren.

BACKGROUND: Poor school performance and low IQ are associated with an increased risk of suicide in males; it is uncertain whether cognitive performance is a risk factor for suicide in females and whether severe mental illness influences these associations.
METHOD: Record linkage study of Swedish education, population and census data with mortality and inpatient registers. Data were available for 95,497 males and 91,311 females born in 1972 and 1977 and followed up until 31 December 2005.
RESULTS: 230 males and 90 females died from suicide over the follow-up period. There were strong inverse associations between school performance at age 16 and subsequent suicide risk in males (fully adjusted hazard ratio (HR) per SD increase in school performance score: 0.6 (95% CI 0.6 to 0.7; p < 0.001)) but not females: adjusted HR. 1.1 (CI 0.9 to 1.4 p = 0.50). In males there were almost four fold differences in suicide risk between children in the top and bottom fifths of the range of school grade scores. Similar associations were seen with upper secondary school performance (age 18/19 years). There was no strong evidence that deterioration in school performance between ages 16 and 18 was associated with increased suicide risk. Amongst men who developed severe psychiatric illness school performance was not associated with suicide risk. LIMITATIONS: We had limited information on the prevalence of minor psychiatric disorder in cohort members and no data on IQ for the cohort as a whole.
CONCLUSIONS: Good performance in secondary (age 16) and upper secondary (age 18) school is associated with a reduced risk of suicide in men but not women. This protective effect is not seen amongst those who develop severe psychiatric illness. These differences indicate that the aetiology of suicide differs in males and females and in those with and without severe mental illness.