Our focus is on electrophysiological endophenotypes, but the approach we recommend is broadly applicable to all endophenotypes. Advances in psychophysiology, such as improved signal processing and statistical methods, are obviously important, but we do not believe that the current level of sophistication used to quantify and process electrophysiological variables is a significant impediment to success in identifying genetic variants associated with endophenotypes. Electrophysiological variables have psychometric properties that are at least equivalent to and in many cases are better than those of phenotypes that have met with success in molecular genetic research. Our focus is on the best practices needed to promote a trait as a suitable endophenotype, and to demonstrate its utility for uncovering biological pathways to the development of psychiatric disorder. Although we believe our recommendations are supported by current practices governing molecular genetic investigations of complex traits, we recognize that there is apt to be some divergence of opinion regarding which practices are indeed optimal. We are not arguing that all endophenotype research must subscribe to our approach, but we do believe that deviation from our recommendations should be accompanied by sound justification.
