Not all offspring have passed through that age of risk for substance use disorder and affective disorders. The patterns of comorbidity identified in this high risk sample may limit generalizability to other young adult cohorts at less risk, but these unique data from offspring of twins provide an insight into patterns of familial risk and developmental psychopathology not otherwise available. Analysis of longitudinal data from the offspring is planned to determine how patterns of comorbidity may change as the offspring age. In addition, it is possible that some offspring were misclassified (e.g., those in the LG, LE group), if their fathers developed SUD later in life. However, the fathers were assessed during middle age (avg. age 42), and epidemiological evidence suggests that the likelihood of an onset of SUD in middle age is quite rare (Wagner and Anthony 2002; Compton et al., 2007), particularly among men of European Ancestry (Grant et al., 2012) as is the case for these twin fathers. It is not possible to measure all environmental influences on offspring. For instance the present study modeled perceptions of
