Comparison of suicide risk and other outcomes among boys and girls who self-harm

Little is known about sex differences in outcomes of self-harm, and there are inconclusive results concerning the association between sex, self-harm, and suicide attempts. The aim of this study was to explore sex differences in outcomes of self-harm in adolescence. In this cohort study, all individuals (0-17 years) enrolled at the child- and adolescent mental health services (CAMHS) in Stockholm between 2001 and 2015 (N = 110,072) were followed in national registers from their last contact with the CAMHS, until end of 2015. Exposure was self-harm as reason for contact, outcome measures were: alcohol-/substance use disorder, psychiatric hospitalization, non-violent or violent crime, and suicide. Differences in outcomes rates between exposed versus unexposed males, and exposed versus unexposed females, were examined using Cox regressions, expressed as hazard ratios (HR) with 95% confidence intervals (CI). Median follow-up time was 5.8 years (Q1: 2.3 years; Q3: 9.7 years). Self-harm was documented in 2.2% (N = 1241) males and 8.7% (4716) females. Exposed individuals had higher HR for all outcomes as compared with unexposed individuals of their own sex. Exposed females had more pronounced risk for drug use disorder (HR 11.2; 95% CI 9.9-12.7) compared with exposed males (HR 6.5, 95% 5.2-8.0). Both males and females who had engaged in self-harm had elevated risks for future suicide. Adjusting for socio-economic status and age at start of follow-up only marginally affected the associations. Females and males with self-harm had similarly elevated risk for suicide, and self-harm was also an important risk marker for other adverse outcomes within both sexes.