Individual differences conducive to aggression and violence: Trajectories and correlates of irritability and hostile rumination through adolescence

This study examined the developmental trends of Irritability and Hostile Rumination at different times over the course of adolescence in a sample of 500 youth. Participants were 12 years old at the time of the first assessment and 20 years old at the last assessment time. Three objectives were pursued: (a) investigation of the stability and change of both Irritability and Hostile Rumination; (b) identification of developmental trajectories of Irritability and Hostile Rumination; and (c) determination of whether different trajectories of Irritability and Rumination were significantly related to physical and verbal aggression and violent conduct at age 20. Results showed that Irritability and Hostile Rumination were highly correlated and stable over time. Four developmental trajectories were identified for both dimensions. Whereas most of the participants demonstrated stable mean levels of Irritability, half of the youth either increased or decreased in their level of Hostile Rumination over time. In addition, high Irritability trajectories were associated with high physical and verbal aggression while high Hostile Rumination trajectories were associated with high levels of violent behavior.