Published online by Cambridge University Press: 04 March 2009
During the transition from early to middle adolescence there are numerous changes internal to the adolescent, such as the onset of puberty and changes in cognitive functioning, and external to the adolescent in terms of social reactions to the adolescent and changes in expectations. These changes may also be explained in terms of genetic and environmental influences on change and stability. This study employs the longitudinal sample from both waves of the Nonshared Environment in Adolescent Development (NEAD) project (395 families). The NEAD project includes adolescent siblings residing in never-divorced families (MZ and DZ twins and full siblings) and in stepfamilies (full, half, and unrelated siblings). The sample was assessed on two measurement occasions, 3 years apart. On average, the first measurement occasion assessed the families during early adolescence and the second measurement occasion occurred during middle adolescence. Composite measures of parent reports, adolescent self-reports and observer ratings of three constructs of adolescent adjustment (antisocial behavior, autonomy, and social responsibility) were examined in this analysis. Each construct showed a different pattern of genetic and environmental contributions to stability and change, suggesting different developmental pathways for each domain of adolescent adjustment. For example, genetic influences were important for both change and stability in antisocial behavior. Stability in social responsibility, on the other hand, was influenced by primarily genetic factors, while nonshared environmental factors were predominantly responsible for change. Finally, genetic and shared environmental influences contributed nearly equally to stability and change in autonomous functioning. These findings emphasize the importance of considering genetic as well as environmental factors when change in development is examined. Additionally, these data provide an armature for a comprehensive developmental theory for each of these domains of adolescent adjustment.