Introduction: In substance abusing families, sources of familial comorbidity are potentially confounded by genetic-environmental (GE) interplays. The children-of-twins (COT) design can be used to elucidate the association of a parental trait and an offspring outcome such as the association of parental alcoholism and offspring suicidality.
Methods: We examined the association of paternal alcoholism and offspring suicidal behaviors in an adolescent and young adult COT sample of 'Vietnam Era Twins' offspring who had completed an interview including a comprehensive assessment of lifetime suicidal behaviors. We stratified the COT sample into four groups contingent upon paternal zygosity, MZ versus DZ, and lifetime paternal alcohol dependence history (AD), positive versus negative. We examined whether the relationship of paternal alcoholism and offspring suicidality was best explained by genetic predispositions common to alcoholism and suicidality or by GE interplay--environmental influences correlated with parental alcoholism or the interaction of genetic and environmental factors.
Results: Our results suggest a main effect of paternal alcoholism on offspring suicide attempt; COT analyses do not support a purely genetic explanation for this association.
Discussion: Suicide attempts probably result from GE interplays and must be studied in genetically informative samples of offspring of substance abusing parents.