Perhaps our most surprising finding was that the small number of individuals who suddenly became above average in aggression at age 30 experienced significant negative consequences later in adulthood. This late-onset aggression group displayed higher levels of aggression, depression, and problem drinking, and poorer health at age 48 than did the life-course-persistent low aggressives. Interestingly, the majority of this group was female, whereas the majority of the other groups was male. There is a wealth of research on “early starters,” or individuals who show serious antisocial behavior at a young age and go on to exhibit the highest levels of general problem behavior [Frick, 2006; Hinshaw et al., 1993; Patterson et al., 1991], and of course Moffitt [1993] has demonstrated the presence of individuals who “flirt” with aggression and antisocial behavior during adolescence. However, the notion that some individuals might be “late starters” controverts the typical view that, on average, aggressiveness declines throughout development. It will be important for future research to examine social experiences or individual liabilities accounting for the emergence of high levels of aggression in early adulthood.
