Next to the genetic etiology of risk behaviors, we recognize the generally known influence of environmental factors. 13 For example cultural, parenting or peer norms can influence substance‐ and sex‐related risky behaviors. What remains largely unknown is to what extent the impact of genetic and environmental risks is additive or interactive. The variants in CADM2 identified here lend themselves well to future gene–environment interaction testing, provided a multi‐cohort study and a combined SNP measure are used to ensure sufficient power.
