Association of Childhood Intrafamilial Aggression and Childhood Peer Bullying With Adult Depressive Symptoms in China.

Importance: Childhood intrafamilial aggression, a series of aggressive behaviors inflicted by family members, and adulthood mental health are associated with childhood peer bullying (eg, in the neighborhood or in school). However, few studies have been able to identify the contribution of childhood peer bullying to the association between childhood intrafamilial aggression and adult depression. Objective: To examine the mediating role of childhood peer bullying in the association between childhood intrafamilial aggression and depression in adulthood. Design, Setting, and Participants: This population-based cross-sectional study used data from the China Health and Retirement Longitudinal Study (CHARLS). Middle-aged and older adults (≥45 years) participated in a CHARLS wave from July 1 to September 30, 2015, and the CHARLS life history survey from June 1 to December 31, 2014, with complete data. A 4-step mediation model with logistic regression was run to test the mediating role of peer bullying. Data analysis was performed from October 1 to 30, 2019. Exposures: Childhood intrafamilial aggression, including parental physical maltreatment and sibling aggression, and peer bullying. Main Outcomes and Measures: Depressive symptoms measured by a categorical variable derived from the Center for Epidemiologic Studies Depression Scale, based on a cutoff score of 12. Results: Among the 15 450 respondents (mean [SD] age, 59.5 [9.9] years; 7987 women [51.7%]), 4422 (28.6%) were exposed to parental physical maltreatment; 986 (6.4%), to sibling aggression; and 2504 (16.2%), to peer bullying in childhood. Respondents experiencing intrafamilial aggression were more likely to be bullied by peers (parental physical maltreatment odds ratio [OR], 2.53 [95% CI, 2.25-2.83]; sibling aggression OR, 3.05 [95% CI, 2.46-3.78]). Children with these adverse experiences were at a higher risk of adult depression symptoms (parental physical maltreatment OR, 1.28 [95% CI, 1.15-1.42]; sibling aggression OR, 1.40 [95% CI, 1.13-1.74]; peer bullying OR, 1.78 [95% CI, 1.56-2.01]). Peer bullying mediated 30% (95% CI, 19%-42%) of the association between childhood parental maltreatment and adult depression and 35% (95% CI, 15%-54%) of the association between sibling aggression and depression symptoms in adulthood. Conclusions and Relevance: This study found that being bullied by peers was a mediator of the association between childhood intrafamilial aggression and depression in adulthood. The findings have important implications to mitigate the effect of early-life stress and promote life-course mental health through dealing with childhood intrafamilial aggression and peer bullying experiences coordinately.