Childhood bullying involvement and later suicidality: longitudinal analyses from The Danish National Birth Cohort

BACKGROUND: Bullying involvement (victim or perpetrator role) in childhood is linked to later suicidality. However, findings are inconsistent, and sex may be a moderator. We investigated whether childhood bullying involvement was associated with suicidality in adolescence, and whether this association varied by sex. METHODS: Childhood bullying involvement was collected from self-reports of children and parents during the 11-year follow-up of the Danish National Birth Cohorts (DNBC). Data on suicidal ideation (SI) and suicide attempts (SA) from the 18-year follow-up were supplemented with hospital records of SA from the National Patient Register. Associations were estimated using multinomial logistic regressions, while inverse probability weighting accounted for socioeconomic-related selection bias. RESULTS: 11 705 boys and 17 292 girls were included. Adolescent boys exposed to bullying had increased risks of SI (adjusted relative risk ratio (aRRR): 1.6; 95% CI: 1.4 to 1.8) and SA (aRRR: 2.8; 95% CI: 2.0 to 3.8), while no increased risk was found among those who were perpetrators of bullying vs non-involved peers. Girl victims had increased risks (aRRR) of SI and SA of 1.6 (95% CI: 1.5 to 1.7) and 2.9 (95% CI: 2.5 to 3.5), respectively. Girl perpetrators had an increased risk of SA (aRRR: 2.3; 95% CI: 1.5 to 3.6). Sex significantly moderated the association between perpetration role and suicidality. CONCLUSION: Childhood bullying was associated with a higher risk of suicidality during adolescence. Girl, but not boy, perpetrators had increased risk of SI and SA. These findings emphasise the importance of preventive interventions targeting bullying in childhood and its long-term effects, including possible differences in policies for boys and girls.