problems and substance use in both sexes [21]. This is in contrast to our findings where only in males the co-occurrence of conduct symptoms and substance use can be mostly explained by overlapping genetic influences. A highly heritable latent phenotype, generally referred to as “behavioural disinhibition” [31], may be implicated in these shared genetic effects. Based on the findings of the present study, this trait seems of particular importance for understanding conduct problems and substance use in males. Future research is needed to replicate the gender differences in the causes of covariation between early conduct problems and later substance use.
