While on one hand the article confirms findings from previous twin and adoption studies that drug abuse is highly heritable (2–4), it also represents a major methodological advance. Previous studies have all relied on twin or adoptee self-report, whereas this study used reports from population-wide registries and thus offers independent confirmation of genetic and environmental influences on drug abuse. While finding genetic effects strengthens the case for investing in studies aimed at understanding the molecular biological underpinnings of the genetic influences on drug abuse, the evidence for family- and community-wide influences on drug abuse are equally important. One problem that bedevils epidemiological studies of drug abuse is understanding the direction of effects. Do individuals or families with drug abuse suffer from “social drift” into a deprived environment, or does a deprived environment cause drug abuse (5)? While the study by Kendler et al. cannot completely disentangle the direction of effects, the authors do demonstrate that above and beyond family-wide influences, there is a community-wide effect on drug abuse, suggesting that deprived communities exert an effect on the development of drug abuse. This suggests that community-wide prevention or intervention programs could ameliorate the development of drug abuse. The example of smoking rates declining through public health efforts suggests that declines in drug abuse could be achieved. On the level of family-wide effects, a finding of note is that years of cohabitation influence the risk of drug abuse, suggesting direct social transmission of drug abuse and a potential target for intervention or prevention strategies. This result should serve as a reminder to clinicians that when one member of a household is experiencing drug abuse, it places other members, particularly younger siblings, at risk (6).