In the present report, we explored a multivariate approach to identifying electrophysiological endophenotypes related to EXT psychopathology. The P3 ERP, its associated TF components, and beta frequency resting state EEG were shown to be heritable and to collectively share genetic variance in EXT, suggesting that these measures may be tapping into common neurophysiological and genetic substrates associated with EXT psychopathology. This shared genetic variance, however, differed as a function of gender. P3 seemed to be more closely related to EXT in males, whereas beta and the TF component were more related in females. Regardless of the gender difference, however, current findings of significant relationships among these electrophysiological endophenotypes and EXT would suggest that a multivariate endophenotype including these measures constitutes a worthy target, in addition to consideration of any of the individual measures, for studies investigating the genetic etiology of externalizing spectrum disorders.
