schizoaffective disorder, mental disorder characterized by a combination of mood (affective) symptoms, such as depression or mania, and schizophrenia symptoms, such as delusions and hallucinations. The term acute schizoaffective psychoses was introduced in 1933 by Russian-born psychiatrist Jacob Kasanin to define a subgroup of psychoses in which affective and schizophrenic symptoms are prominent simultaneously, within a few days of each other or within the same episode of illness. Historically, other concepts, such as intermediate psychoses and mixed psychoses, were used to describe the psychoses between affective and schizophrenic disorders. However, Kasanin’s terminology persisted, giving rise to the subgroup known simply as schizoaffective disorders.

The specific cause or causes of schizoaffective disorders remain unknown. However, two types of schizoaffective disorders have been established based on affective symptoms. One is bipolar type, if the mood disturbance includes a manic or a mixed (manic and depressive) episode, and the other is depressive type, if the mood disturbance includes only major depressive symptoms. Patients often suffer from recurrent episodes and thus need preventive treatment. Most patients, however, make a full recovery, and only a small percentage of cases end in chronicity or a defect state.