Abstract
The study of delinquent peers has remained at the forefront of much criminological research and theorizing. One issue of particular importance involves the factors related to why people associate with and maintain a sustained involvement with delinquent peers. Although efforts have been made to address these questions, relatively little attempt has been made to understand these relationships from a biosocial perspective. This gap in the literature is addressed in an analysis of twins from the National Longitudinal Study of Adolescent Health (Add Health). The results of the univariate behavioral genetic models reveal that genetic factors account for between 58% and 74% of the variance in the association with delinquent peers, with the remaining variance attributable to environmental factors. Bivariate Cholesky decomposition models reveal that genetic factors account for 58% of the variance in the stability in delinquent peers. The shared environment explains 34% of the variance in stability, and the remaining 8% is attributable to the nonshared environment. The importance of a biosocial approach in criminological research is discussed.