Conduct Disorder

Certain neuropsychological indicators (influences in the brain that are linked to psychological functioning) are linked with aggression. Aggression and impulsiveness are associated with structural abnormalities related to thought processing and inhibition of behavior. Deficits in certain neurochemicals, including serotonin and norepinephrine, are also linked to behavior problems. Reductions in the functioning of the autonomic nervous system, which is responsible for the regulation of bodily processes, is also linked to chronic conduct problems. In particular, low-resting heart rate and low-skin conductance are frequently present in individuals with persistent behavior problems. These deficits and resultant reductions in behavioral inhibition are characteristic of both CD and ADHD.

Contemporary theories accentuate a dynamic interplay between biological and environmental factors and propose that most of the effects of a person's biological constitution on CD are mediated through disrupted parenting and peer environments (Deater-Deckard and Bullock, in press). There is some evidence that child-onset CD, characterized by antisocial behavior and hyperactivity, may have stronger biological underpinnings than later-onset CD. Exploration of reciprocal transactions between genes and the environment suggests that children may evoke reactions from parents and others that contribute to antisocial behavior (Rutter et al. 1997).

Individual differences in infant temperament are also directly implicated in behavioral development, with mothers' ratings of children's difficult and hyperpersistent temperament at six months predicting later teacher ratings of conduct difficulties. Studies of adoptees at genetic risk for conduct problems also indicate that genetically compromised children are more likely to experience harsh, negative parenting in their adoptive families, compared to children without a liability for problem behavior (Ge et al. 1996).

Some theorists propose that individuals actively select environments and relationships consistent with their genetic disposition (Scarr and McCartney 1983), with antisocial youth selecting peers who reinforce deviance. Although little research focuses on the biological characteristics that contribute to the influence of deviant peers in early adolescence, the ability of individuals to regulate their behavior and emotions seems to be a promising candidate. Many other biologically oriented constructs have been proposed, but none have clarified whether such constructs are causally unique or simply by-products of being raised in a harsh family environment from an early age.