externalizing phenotypes (ADHD, problematic alcohol use, lifetime cannabis use, age at first sexual intercourse, number of sexual partners, risk-taking, and lifetime smoking initiation). The model included data from 1.5 million EA individuals and indicated a single genetic factor underlying the externalizing behaviors (Karlsson Linnér et al., 2021), paralleling findings from twin data. More than 500 loci were associated with the externalizing factor at levels surpassing genome-wide significance. These loci were enriched for genes expressed in the brain and related to development of the nervous system (Karlsson Linnér et al., 2021).
