Familial transmission of derived phenotypes for molecular genetic studies of substance use disorders.

Although family, twin, and adoption studies indicate that genes play a significant etiologic role in the development of substance use disorders (SUDs), detecting specific genes has been difficult due to uncertainties about how to define SUDs, genetic heterogeneity and variable phenotypic expression of SUD genotypes. We used data from families recruited into six contemporaneous studies of children and adults to derive candidate SUD phenotypes using principle factors factor analysis with varimax rotation. We previously found evidence of two SUD phenotypes in offspring: a psychopathology dimension and a cognitive impairment dimension. We found evidence for one SUD-related phenotype in adults that we term Psychopathology and Cognitive Impairment. Parental factor scores significantly predicted both offspring phenotypes, as well as parental SUD (OR=1.41, p<0.001) and offspring SUD (mother's phenotype: OR=1.34, p=0.04; father's phenotype: OR=1.33, p=0.01). Offspring phenotype predicted offspring SUD (psychopathology phenotype: OR=2.96, p<0.001; cognitive impairment: OR=1.33, p=0.04); in offspring, baseline psychopathology predicted SUD at follow-up assessments (OR=1.55, p=0.01). Results suggest that these candidate SUD phenotypes may be useful for genetic studies of SUD.