An important, novel finding in the present report was differential patterns of shared genetic variance as a function of gender. In males, the TF and beta endophenotypes accounted for an additional, yet non-significant, increment in genetic variance in EXT above that accounted for by P3; whereas in females, the TF and beta endophenotypes did account for significant variance above and beyond that shared with P3. Based on these results, the question arises as to the best way to utilize these endophenotypes collectively in genetic studies. Two possibilities emerge: 1) use a multivariate endophenotype that is specific to each gender, thus requiring two “passes” in the search for EXT-related genes, each of which may be ideally suited for males or females, or 2) use the same multivariate endophenotype for both genders, which requires only one pass at the data, but may include a measure that is not associated with significant variance in EXT. Given the depth of information contained in the genetic code, we submit that the latter approach may be the more fruitful one 1) in terms of efficiency, and
