ABSTRACT
The endophenotype approach to psychosis Using conventional clinical diagnoses as the sole phenotype may not be optimal for the genetic dissection of complex (non-Mendelian) psychiatric diseases such as schizophrenia, bipolar disorder or psychosis. Psychiatric diagnoses are based on symptomatic definitions that reflect much heterogeneity (Begleiter & Porjesz, 2006; Gottesman & Gould, 2003). There is a growing recognition that common mental disorders, such as schizophrenia, bipolar disorder, and depression, are caused by numerous genetic and environmental factors, each of which have individually small effects and which only result in overt disease expression if their combined effects cross a hypothetical “threshold of liability” (Falconer, 1965).
