Multiple research groups have demonstrated that individual differences in behavioral disinhibition are largely genetic in origin (Krueger et al., 2002; Young et al., 2000). In a previous study from our group (Young et al., 2000), we explicitly tested a hierarchical model (also referred to as a common pathway model) of behavioral disinhibition, which hypothesizes that there are genetic and environmental influences that operate on an underlying common liability (i.e., a common factor) shared among adolescent externalizing problems. We applied this model to an adolescent twin sample, which included a small subsample of the longitudinal twins in the current study when they were 12 years of age. Using measures comparable to the current study, we reported a highly heritable general liability factor (a2 = .82). Krueger et al. (2002) tested a similar model of what they termed the externalizing spectrum (representing the covariance among symptoms of antisocial personality, conduct disorder, alcohol and drug dependence, and unconstrained personality style), reporting a similar estimate of heritability of .81 in their sample of 17-year-old twins. Taken together, these results provide compelling evidence that etiology of the common underlying pathology is primarily genetic, while leaving open questions about the nature of the pathology itself.
