These analyses have several important limitations. We recognize that both our GWAS and additional meta analyses were severely underpowered. Sample sizes in the hundreds of thousands or more are necessary to identify robust genetic signals. Second, our measure of externalizing was mostly limited to criteria for psychiatric disorders. There are other heritable dimensions of personality, like sensation seeking and impulsivity, related to these behaviors not captured in the current phenotype (Krueger et al., 2002).
