function reasonably well in school and with their peers (Offord et al., 1992; Weiss and Hechtman, 1986).
Conduct disorder is important not only because of its relatively high frequency and occurrence with other disorders, but also because of its persistence into adolescence and adulthood. In one community study, 6 percent of boys and 1.6 percent of girls aged 6 to 11 and 10.4 percent of boys and 4.1 percent of girls aged 12 to 16 were diagnosed as having conduct disorder (Offord et al., 1989a). Forty percent of children with conduct disorder between ages 8 and 12 still had the disorder at follow-up four years later (Offord et al., 1992). Still other children who had conduct disorder at 8 to 12 years had substance abuse at follow-up four years later, although they did not show other features of conduct disorder. The pattern of conduct disorder symptoms most predictive of later drug abuse or delinquency is a combination of aggression and shyness (Moskowitz and Schwartzman, 1989; McCord, 1988; Kellam, Brown, Rubin, and Einsminger, 1983). Aggression accompanied by peer rejection, rather than aggression alone, predicts later delinquency. Furthermore, 50 percent of adolescents with conduct disorder go on to show persistent antisocial disorders in adult life (Rutter and Giller, 1983). Conduct disorder not only predicts later mental disorders in adulthood but also has wide-ranging poor prognosis in adult life with higher rates of school failure, joblessness, and poor interpersonal skills, especially marital difficulties (Robins, 1970). As adults, males have more externalizing disorders (such as antisocial personality disorders and alcohol and drug abuse) than females, and females have more internalizing disorders (such as mood and anxiety disorders) (Offord, 1989).
The antisocial behavior patterns that form the core of the conduct disorder diagnosis show considerable stability over the life course. When the patterns that had their onset in childhood or adolescence continue into adulthood, the name of the disorder changes, but the diagnostic criteria remain very similar. For the DSM-III-R diagnosis of antisocial personality disorder to be made, the individual must be at least 18 years of age, have a history of conduct disorder beginning before age 15, and demonstrate a pattern of irresponsible and antisocial behavior (meeting at least 4 of 10 diagnostic criteria) since age 15 (see Table 5.2). In adulthood the failure to conform to social norms often takes the form of impulsive and reckless behavior, poor work behavior, irritability and aggressiveness, and illegal activity that may result in incarceration and early death through various forms of violence. In the ECA study, about 0.5 percent of adults met the criteria for DIS/DSM-III antisocial personality disorder at a given point in time (conduct disorder was not studied because the focus in the ECA study was on adults), and