The disorders in this section include Schizophrenia, Schizophreniform Disorder, Schizoaffective Disorder, Delusional Disorder, Brief Psychotic Disorder, Shared Psychotic Disorder, Psychotic Disorder Due to a General Medical Condition, Substance-Induced Psychotic Disorder, and Psychotic Disorder Not Otherwise Specified. These disorders have been grouped together to facilitate the differential diagnosis of disorders that include psychotic symptoms as a prominent aspect of their presentation. Other disorders that may present with psychotic symptoms as associated features are included elsewhere in the manual (e.g., Dementia of the Alzheimer's Type and Substance-Induced Delirium in the "Delirium, Dementia, and Amnestic and Other Cognitive Disorders" section; Major Depressive Disorder, With Psychotic Features, in the "Mood Disorders" section). Despite the fact that these disorders are grouped together in this chapter, it should be understood that psychotic symptoms are not necessarily considered to be core or fundamental features of these disorders, nor do the disorders in this section necessarily have a common etiology. In fact, a number of studies suggest closer etiological associations between Schizophrenia and other disorders that, by definition, do not present with psychotic symptoms (e.g., Schizotypal Personality Disorder).