Table 1 lists commonly investigated endophenotypes in psychiatry and reveals a number of features. First, a small number of endophenotypes have attracted disproportionate attention. Second, work on many endophenotypes often predates the development of the endophenotype concept and goes beyond its concern with genetics. Interest in endophenotypes reflects a longstanding interest in investigating the biological correlates of psychiatric disease. Third, endophenotypes can be categorized into six groups: anatomical, developmental, electrophysiological, metabolic, sensory or psychological/cognitive. Fourth, we identified papers claiming endophenotypes for just seven psychiatric disorders. Together, these observations indicate that there is plenty of scope to find new endophenotypes in psychiatry, both by analysis of other psychiatric disorders and by searching for new features that have the relevant characteristics.
