Psychotic disorders are syndromes characterized by the presence of psychosis. The term psychosis denotes an abnormal mental status characterized by various forms of bizarre, disorganized behavior, disorganized or illogical thinking, misperception, and distortion of reality. Specific terms used to describe psychotic mental states include delusions and hallucinations. Psychosis as a phenomenon is not specific, nor is it pathognomonic for any single diagnosis, health condition, or particular etiology. As psychotic symptoms can result from numerous medical, neurological, and psychiatric illnesses, the presence of psychosis should prompt a search for the underlying etiology. Psychosis is considered “primary” when there is no identifiable inducing agent or medical condition. On the contrary, psychosis is considered “secondary” when the psychotic symptoms are induced by an identified medical or neurological condition, prescribed medications, drugs of abuse, exposure to toxins, or other causes. This chapter focuses on primary psychotic disorders including brief psychotic disorder, schizophreniform disorder, schizophrenia, schizoaffective disorder, and delusional disorder. The diagnostic criteria, epidemiology, genetics, neurobiology, clinical manifestations, and treatment of each psychotic disorder are described. However, more space will be dedicated to schizophrenia, as it is the prototypical psychotic disorder.
