Examining the joint development of antisocial behavior and personality: Predictors and trajectories of adolescent indirect aggression and machiavellianism.

Indirect aggression has been associated with antisocial personality traits like Machiavellianism, but there is a lack of evidence on their longitudinal development across adolescence. Therefore, the joint developmental trajectories of adolescent indirect aggression and Machiavellianism across 3 years of high school (Grades 10 to 12) were investigated. Predictors of joint trajectory groups at the start of high school (Grade 9) were also explored. Participants included a sample of 513 individuals ( = 14.95 in Grade 10; = .37; 56.7% girls; 76.4% White) recruited from a school district that completed self-report measures of indirect aggression and Machaivellianism annually. Self- and parent-report measures of individual differences (e.g., approval seeking), peer relations (e.g., school bonding), and psychological features (e.g., anxiety) were explored as predictors of the trajectory groups. As predicted, a small subgroup of individuals indicated a high-risk joint trajectory pattern of moderate stable indirect aggression and high stable Machiavellianism. Additional trajectory patterns included a low-risk group indicating low stable indirect aggression and low stable Machiavellianism, and a high Machiavellianism only group indicating low stable indirect aggression and high stable Machiavellianism. Moderate indirect aggression was a better indicator of high Machiavellianism than the reverse. Individual differences, peer relations, and psychological features differentiated these trajectory groups. Findings have implications for the prevention of antisocial traits and behavior among young people. (PsycInfo Database Record (c) 2021 APA, all rights reserved).