Course and Natural History
Some behaviors characteristic of the AD-DBDs are observable as early as the preschool years. Hyperactive behaviors such as “moves too much during sleep” have been reported as early as age one and a half years, followed by the appearance of “difficulty playing quietly” and “excessive climbing/running” by age 3 years. Attentional problems are usually reported after hyperactivity. However, it is likely that these problems are present from early on but are not reported until the child enters school, when there are increased en-vironmental and cognitive demands. Hyperactivity and attentional problems emerge gradually and may overlap with the emergence of oppositional behaviors. Many individuals with ADHD continue to have attentional, behavioral and emotional problems well into adolescence and adulthood. Typically, adults with ADHD are less overtly overactive, although they may retain a subjective sense of restlessness. Impairment in these adults is more often a result of inattention, disorganization and impulsive behavior.
During the preschool years, transient oppositional behav-ior is very common. However, when the oppositionality is of a persistent nature and lasts beyond the preschool years, the esca-lation to more disruptive behaviors is more likely. In most oppo-sitional children, who are usually not physically aggressive, op-positional behaviors peak around age 8 years and decline beyond that. In a second group of children, delinquent behaviors follow the onset of oppositional behaviors. Early physical aggression is a key predictor of this latter trajectory, with physically aggres-sive children being more likely to progress from early opposi-tional behaviors to more severe and disabling conduct problems. Coexistent ADHD tends to speed this escalation to more severe conduct problems and the development of antisocial personality disorder in adulthood.
Generally, conduct problems first appear in middle child-hood. The progression of conduct problems is from rule viola-tions, such as poor school attendance, to aggression toward ani-mals and people. In males, the progression to more serious forms of conduct problems, such as rape or mugging, generally emerge after age 13 years (Loeber, 1990). A different group of children show conduct problems for the first time during adolescence, without preexisting oppositional or aggressive behaviors. This latter group tends to have disorders that are transient and nonag-gressive. When conduct disorder is seen in adolescence for the first time, the problems tend to diminish by adulthood. However, if conduct disorder is present from middle childhood, there is a much greater degree of persistence of aggression through adult-hood and often a history of arrests and/or incarceration.
Considerable data indicate that a subgroup of hyperactive children show high rates of delinquency and substance abuse during adolescence, and this continues into adulthood. However, it is likely due to the comorbidity with conduct disorder or bipolar disorder that higher rates of substance abuse are found in ado-lescents with ADHD. Families of these children tend to be less stable, have higher divorce rates and move more frequently. First degree relatives have been found to have higher rates of antisocial behaviors, substance abuse and depression The difficulties expe-rienced by these adolescents and adults include poor self-esteem, difficulty in interpersonal relationships, difficulties in holding onto jobs, as well as assault and armed robbery in a minority of cases (Hechtman et al., 1981).