A poor prognosis was assumed to apply to these patients by most clinicians, and this poor prognosis was harmful to many patients. The poor prognosis for DSM-IV schizoaffective disorder was not based on patient outcomes research, but was caused by poorly defined criteria interacting with clinical tradition and belief; clinician enculturation with unscientific assumptions from the diagnosis history (discussed above), including the invalid Kraepelinian dichotomy; and by clinicians being unfamiliar with the scientific limitations of the diagnostic and classification system.The DSM-5 schizoaffective disorder workgroup analyzed all of the available research evidence on schizoaffective disorder, and concluded that "presenting symptoms of psychosis have little validity in determining diagnosis, prognosis, or treatment response." Given our understanding of overlapping genetics in bipolar disorders, schizoaffective disorder, and schizophrenia, as well as the overlap in treatments for these disorders; but given the lack of specificity of presenting symptoms for determining diagnosis, prognosis or treatment response in these psychotic illness syndromes, the limits of our knowledge are clearer: Presenting symptoms of psychosis describe only presenting symptoms to be treated, and not much more. Schizoaffective disorder was changed to a longitudinal or life course diagnosis in DSM-5 for this reason. Research
Little is known of the causes and mechanisms that lead to the development of schizoaffective disorder.
Notable patients
Avigdor Arikha – Paris-based painter and art historian
David Brudnoy – Boston talk radio host
Al Copeland – New Orleans entrepreneur, powerboat racer
Al Davis – Principal owner of the Oakland Raiders of the National Football League
Ed Derwinski – U.S. Representative from Illinois and 1st Secretary of Veterans Affairs
Leonard Hirshan – Showbusiness agent and manager. Max Perutz – Nobel Prize–winning chemist
Lindsay Thompson – Former Premier of Victoria, Australia
Joe Zawinul – Jazz-fusion keyboardist and composer
John Fitch – Race car driver and road safety pioneer
Carl Mundy – 30th Commandant of the United States Marine Corps
Geoffrey Penwill Parsons – Pianist
Maria Bueno – Tennis player

References
External links
 Media related to Merkel cell carcinoma at Wikimedia Commons
National Cancer Institute. "Merkel Cell Carcinoma". National Institutes of Health (US). Archived from the original on 2010-12-21. Retrieved 2011-01-20.