Background: As the suicide rates in young adults do not show a clear decline, it is important to elucidate possible risk factors. Juvenile delinquency has been pointed out as a possible risk behaviour.
Methods: This register-based cohort study comprises the birth cohorts between 1972 and 1981 in Sweden. We followed 992,881 individuals from the age of 20 years until 31 December 2006, generating 10 210 566 person-years and 1482 suicides. Juvenile delinquency was defined as being convicted of a crime between the ages of 15 and 19 years. Estimates of risk of suicide were calculated as incidence rate ratio (IRR) with 95% confidence intervals (CIs) using Poisson regression analysis with adjustment for potential confounding by their own and their parents' mental illness or substance abuse, parental education, single parenthood, social assistance, adoption and foster care.
Results: Among females, 5.9%, and among males, 17.9%, had at least one conviction between the ages 15 and 19 years. In the fully adjusted model, females with one conviction had a suicide risk of 1.7 times higher (95% CI 1.2-2.4), the corresponding IRR for men was 2.0 (95% CI 1.7-2.4) and 5.7 (95% CI 2.5-13.1) and 6.6 (95% CI 5.2-8.3), for women and men with five or more convictions. The effect of severe delinquency on suicide was independent of parental educational level.
Conclusions: This study supports the hypothesis that individuals with delinquent behaviour in late adolescence have an increased risk of suicide as young adults. Regardless of causality issues, repeated juvenile offenders should be regarded by professionals in health, social and correctional services who come into contact with this group as a high-risk group for suicide.