We contend that best practice endophenotype research should be designed to address the topics listed in Table 1. These topics are grouped into three domains, representing three important aspects of construct validation (Cronbach & Meehl, 1955a) applied to endophenotypes. The first, threshold criteria, describe the minimum requirements any biomarker must satisfy to have standing as a putative endophenotype. The second, endophenotype verification, identifies the requirements necessary to remove the qualifier “putative” or “candidate” from an endophenotype's status. Compared to the first domain, there is far less endophenotype research targeting verification. The third domain deals with utility. While the topics listed here also enhance construct validity, they cover usefulness of an endophenotype, how it can be used as a research tool to advance knowledge regarding the biological etiology of psychiatric disorder. To prove its worth, an identified endophenotype should enable researchers to achieve the verification and utility topic goals. Thus far, few endophenotype investigations adequately tackle these aims.
