Cross-generational transmission from drug abuse in parents to attention-deficit/hyperactivity disorder in children.

BACKGROUND Attention-deficit/hyperactivity disorder (ADHD) predisposes to drug abuse (DA) and twin studies suggest shared genetic effects. We here seek to determine, using adoption and adoption-like samples, the magnitude of the cross-generational transmission from DA in parents to ADHD in their children and clarify the degree to which this arises from genetic v. rearing effects. METHOD We ascertained ADHD and DA from multiple Swedish registries. Statistical analysis was performed by Cox and path models. RESULTS Risk for ADHD was significantly and similarly increased in the offspring of biological mothers and fathers with DA who did v. did not rear their offspring. Risk for ADHD was not elevated in the offspring of adoptive or step-parents with DA. CONCLUSIONS Cross-generational transmission was observed from DA in parents to ADHD in their children. An analysis of adoptive and adoptive-like parent-offspring relationships suggested that this transmission results from genetic and not from rearing effects.