Family study data are central to establishment of the origin of mutations, that is, inherited or de novo, from both sequencing and structural variation data, and play a vital role in establishing the inheritance of both phenotypes and genotypes across generations. 137 Evaluation of families will allow for the evaluation of both common and rare variants, as well allowing researchers to evaluate environmental risk factors in a way that is not possible in case‐control studies. Specifically including sex differences in the study design and prospectively studying sex differences across development in families will be vitally important to examining potential genetic and environmental mechanisms for sex differences. Systematic recruitment by sex of the proband and prospective designs that examine the sex‐ratio and potential influences across development may provide insight not only on the emergence of sex differences but also their underlying causes.
