Mean kids become mean adults: Trajectories of indirect aggression from age 10 to 22.

Although much is known about the development of physical aggression across the lifespan, far less is known about the developmental pattern of indirect aggression from childhood to adulthood. Accordingly, we examined the self-reported use of indirect aggression from age 10 to 22 in a randomly drawn sample of 704 Canadians. A person-centered approach was used to capture intraindividual change and heterogeneity in development. Four childhood (age 10-18) indirect aggression trajectories were identified: (1) a very low decreasing group (64.8%), (2) a low decreasing group (26.0%), (3) a low-to-moderate increasing group (5.1%), and (4) a moderate increasing group (4.1%). There were more girls than boys in the moderate increasing group (75.9% vs. 24.1%). Two adulthood (age 19-22) indirect aggression trajectory groups were also identified: (1) a low decreasing group (82.6%), and (2) a moderate stable group (17.4%). No sex differences were found among adults' use across the two trajectories. When we examined the prediction of indirect aggression use in adulthood from indirect aggression use in childhood, we found that children who followed a moderate increasing trajectory from age 10 to 18 were nine times more likely to follow a moderate stable trajectory from age 19 to 22, while children who followed a low-to-moderate increasing trajectory across childhood were 14 times more likely to follow a moderate stable trajectory across adulthood (compared to the very low decreasing group). Given the negative impact indirect aggression has on others, intervening early to derail this pattern of abuse is justified.