Young adult self-harm: The role of victimisation and polygenic risk in a population-based longitudinal study.

Background: Victimisation has been associated with self-harm (with or without suicidal intent), but little is known about this association during young adulthood-a distinct developmental period. Further, not all individuals who experience victimisation will later engage in self-harm, suggesting the influence of other factors. The present study examined whether perceived victimisation is associated with self-harm during young adulthood while adjusting for confounders such as peer victimisation and mental health difficulties in adolescence. Additionally, we investigated whether genetic susceptibility for mental health difficulties moderates this association. Methods: Participants were from the Quebec Longitudinal Study of Child Development (1998-2023); a population-based birth cohort from the Canadian province of Quebec, with victimisation and self-harm measures in young adulthood (sample 1; Results: Overall, 17.2% (sample 1) participants reported self-harm at age 20-25 years. Victimisation was associated with self-harm (OR = 1.66, 95% CI = 1.45, 1.89, for each standard deviation increase in victimisation), even after adjusting for confounders, for example, victimisation and mental health in adolescence (OR = 1.53, 95% CI = 1.26, 1.86). In sample 2, PGSs for depression and suicide attempt (not ADHD) were associated with self-harm as well as victimisation in young adulthood, and none moderated the association between victimisation and self-harm. Conclusion: Regardless of genetic susceptibility indexed by PGSs, young adult exposed to victimisation are at higher risk of self-harm. Continuing efforts to prevent victimisation beyond childhood/adolescence and into young adulthood may contribute to reducing self-harm risk.