Interestingly, Piletz and colleagues believe the contents of the database highlight the "nagging likelihood" that the diagnosis
of bipolar disorder might not itself be an entirely suitable phenotype to study, citing the existence of two recognized subtypes
of the disorder (BD1 and BD2), both of which run together in pedigrees, and the fact that major depressive disorder, schizoaffective
disorder, and schizophrenia are represented in most families of bipolar disorder probands. "Bipolar disorder may be best considered
as a spectrum disorder," they said.