Endophenotypes for bipolar disorder

Professor James Potash describes how endophenotypes are used to study bipolar disorder. Endophenotypes are essentially subtypes of larger symptoms.

Because we think that there probably are many, many genes involved in susceptibility to bipolar disorder; we’re thinking it may be dozens; it may be more than that. One approach to isolate the effects of individual genes or a particular gene variance would be to get a more homogeneous set of people to study or phenotype to study. One approach that we are using at [Johns] Hopkins and some other groups around the world are doing as well is to look at clinically defined homogeneous subtypes; so for example only the subset of people who have psychotic symptoms, that is hallucinations and delusions which is about half of the people with bipolar [disorder] 1. We are also interested in only looking at people who have an early onset of illness, so if you only look at people whose illness begins in childhood or adolescence you might have a more homogeneous subset.