As a whole, the present study brings large-scale gene identification efforts into a developmental psychopathology framework to better understand gene-behavior associations. Applying GWAS results for adult externalizing disorders to younger samples and conducting more fine-grained gene-by-development and gene-by-environment analyses is an important integration of the current best practices in genetics research with the types of research questions that are of key interest to psychologists. It is encouraging to see that measured genotypic results are consistent with gene-by-development and gene-by-environment findings from twin samples, particularly in view of the criticisms of twin methods (for a review of these critiques see Tenesa & Haley, 2013). Twin models characterize “genetic influence” latently, by inferring genetic influence based on differences between relatives with varying degrees of genetic sharing. Polygenic risk scores provide a specific measure of genetic risk based on measured genotypes. The fact that divergent methods produce convergent results provides compelling evidence for the developmental and gene-by-environment effects reported here. Further, polygenic approaches have the advantage of providing a more global index of genetic risk goes beyond widely-criticized and only nominally informative candidate
