Recently, multivariate methods for gene identification have been developed (Grotzinger et al., 2019) that allow one to model genetic covariance (the degree to which there is genetic sharing across outcomes) in a way that parallels factor models of phenotypic covariance. These methods allow researchers to use our understanding of the genetic architecture of behavioral traits to aid in gene identification, capitalizing on decades of twin research that elucidates how genetic influences impact behavioral and psychiatric outcomes.
