The larger and more diverse effects demonstrated in biologically related families are consistent with other family studies in implicating the existence of a common inherited liability across multiple indicators of disinhibition. For example, relatives of alcoholics have elevated rates of smoking and illicit drug dependence28, and the inherited factors that underlie conduct disorder overlap extensively with those for alcoholism29, 30 and drug dependence31, 32. More generally, there appears to be a common familial liability to disinhibitory disorders10, due in large part to a general genetic vulnerability33. Research in adolescent samples also confirms the existence of a common genetic liability underlying both behavioral and dispositional markers of risk34, 35.
