Abstract / Summary
Abstract Background Cumulative family adversity is a well-established antecedent of adolescent aggressive behavior; however, it remains unclear whether this relationship follows a linear or nonlinear pattern and whether it varies across individuals. This study therefore aimed to examine how cumulative family adversity increased the risk of aggressive behavior and whether this association was moderated by serotonergic genes. Methods Participants were 1,088 adolescents followed from age 11 to 14 ( M age = 12.56 ± 0.34 years old at Time 1, 50.1% girls). Mother-reported family socioeconomic status, mother-reported negative parenting, adolescent-reported parent-child conflict, and teacher-reported adolescent aggressive behavior were assessed at Time 1 to Time 4, respectively. Adolescents’ saliva samples were collected at Time 2. Hierarchical regression analyses were conducted to examine the relationship between cumulative family risk and adolescent aggressive behavior, as well as the moderation of serotonergic genes. Results The association between cumulative family risk and aggressive behavior showed a nonlinear, J-shaped pattern. Specifically, adolescents exhibited relatively low aggressive behavior at low levels of adversity, but their aggressive behavior escalated sharply once cumulative risk surpassed a critical threshold. Furthermore, the nonlinear relationship was observed only among adolescents carrying a greater number of low-serotonergic alleles, whereas no linear or nonlinear associations were found in their higher‑serotonergic counterparts. Conclusions These findings indicate that adolescent aggressive behavior is shaped by genotype-specific, threshold-dependent stress responses. They also support prevention and intervention strategies that integrate both cumulative environmental risk and individual genetic vulnerability to improve effectiveness in reducing adolescent aggressive behavior.