Only one other known investigation using a twin design to control for common familial influences has reported on the association between CSA and lifetime substance use, a study by Nelson and colleagues (7) in which women exposed to CSA were significantly more likely than their unexposed co-twins to report using cannabis. The majority of co-twin control studies of CSA have focused on substance use disorders. Our results also parallel their findings of elevated rates of alcohol use disorders (5–7), nicotine dependence (6, 7), and cannabis dependence (5, 6) after controlling for genetic and shared environmental influences. Among them is Kendler et al.’s (5) study of psychiatric and substance use disorders in women, in which the authors concluded that the observed pattern of results was consistent with a causal relationship between CSA and psychiatric and substance use disorders.
