Complex sentence: Schizoaffective disorder is a psychiatric diagnosis that describes a mental disorder characterized by recurring episodes of elevated or depressed mood, or of simultaneously elevated and depressed mood (called a mixed state or mixed episode) that alternate with, or occur together with, distortions in perception.
Split into simpler sentences: Schizoaffective disorder is a psychiatric diagnosis that describes a mental disorder characterized by recurring abnormal mood and psychotic components. The mood component may be elevated or depressed, or simultaneously elevated and depressed (mixed episode), and these abnormal mood components alternate with, or occur together with, distortions in perception.