School performance and hospital admissions due to self-inflicted injury: a Swedish national cohort study

Background Self-inflicted injury in youth has increased in many Western countries during recent decades. Education is the most influential societal determinant of living conditions in young people after early childhood. This study tested the hypothesis that school performance predicts self-inflicted injury. Methods A national cohort of 447929 children born during 1973-77 was followed prospectively in the National Patient Discharge Register from the end of their ninth and last year of compulsory school until 2001. Multivariate Cox analyses of proportional hazards were used to test hypotheses regarding grades in ninth grade as predictors of hospital admission due to self-inflicted injury. Results The risk of hospital admission because of self-inflicted injury increased steeply in a step-wise manner with decreasing grade point average. Hazard ratios were 6.2 (95% confidence interval 5.5-7.0) in those with the lowest level of grade point average compared with the highest. The risks were similar for women and men. Adjustment for potential socio-economic confounders in a multivariate proportional hazards regression analysis attenuated this strong gradient only marginally. Conclusion School performance is a strong factor for predicting future mental ill-health as expressed by self-inflicted injury.