Introduction to Schizophrenia and Related Disorders By Carol Tamminga, MD, UT Southwestern Medical Dallas Reviewed / Revised Apr 2022 | Modified Sep 2022 View Patient Education Schizophrenia and related psychotic disorders— brief psychotic disorder, delusional disorder, schizoaffective disorder, schizophreniform disorder, and schizotypal personality disorder —are characterized most prominently by psychotic symptoms and often by negative symptoms and cognitive dysfunction.