Association Between Deliberate Self-harm and Violent Criminality

IMPORTANCE Individuals who self-harm may have an increased risk of aggression toward others, but this association has been insufficiently investigated. More conclusive evidence may affect assessment, treatment interventions, and clinical guidelines. OBJECTIVE To investigate the association between nonfatal self-harm and violent crime. DESIGN, SETTING, AND PARTICIPANTS This population-based longitudinal cohort study, conducted from January 1, 1997, through December 31, 2013, studied all Swedish citizens born between 1982 and 1998 who were 15 years and older (N = 1 850 252). Individuals who emigrated from Sweden before the age of 15 years (n = 104 051) or immigrated to Sweden after the age of 13 years (ie, <2 years before the beginning of the follow-up; n = 22 009) were excluded. Data analysis was performed from April 21, 2016, to June 4, 2016. EXPOSURES Receipt of self-harm-associated clinical care. MAIN OUTCOMES AND MEASURES Conviction of a violent crime according to the Swedish penal code. RESULTS The study cohort consisted of 1 850 525 individuals (950 382 males and 900 143 females), and the mean (SD) follow-up time was 8.1 (4.7) years (range, 0-17.0 years; minimum age, 15 years; maximum age, 32 years). During a mean follow-up period of 8.1 years, 55 185 individuals (3.0%) received clinical care for self-harm. The crude hazard ratio was 4.9 (95% CI, 4.8-5.0) for violent crime conviction in exposed individuals compared with the unexposed group. Women who self-harm were at particularly high risk for expressing violent behaviors. After adjustment for relevant psychiatric comorbidities and socioeconomic status, an almost doubled hazard of violent offense remained (hazard ratio, 1.8; 95% CI, 1.8-1.9). CONCLUSIONS AND RELEVANCE Self-harm is associated with an increased risk of conviction for a violent offense in both sexes. The risk of violence, as well as the risk of suicide and self-harm, should be assessed among offending and self-harming individuals.