No question in psychiatric nosology has attracted such consistent controversy over the past several generations as the setting of the boundary between schizophrenia and major mood disorders. Indeed, Kraepelin,1 the originator of this diagnostic distinction, was well aware of the difficulties of defining precisely this boundary. A closely related question has been whether there exists, between these 2 pivotal diagnostic entities, a third valid disorder that shares some clinical features with each: schizoaffective disorder (SAD).
Kendler KS. Psychosis Within vs Outside of Major Mood EpisodesA Key Prognostic and Diagnostic Criterion. JAMA Psychiatry. 2013;70(12):1263–1264. doi:10.1001/jamapsychiatry.2013.2808