Psychosis is a term that describes severe mental disturbance, not a specific disorder. Many disorders have symptoms of psychosis including: Schizophrenia, Schizophreniform Disorder, Brief Psychotic Disorder, Schizoaffective Disorder, Delusional Disorder, Psychotic Disorder Due to Another General Medical Condition, Substance/Medication-Induced Psychotic Disorder, and Unspecified and Other Specified Psychotic Disorder. These disorders are clinical syndromes, not discrete diseases.

Most psychotic disorders do not have clear etiology. Of course, the disorders related to medical conditions and substance withdrawal are more easily traced to a precipitating factor and are therefore more likely to be easily diagnosed.

Evaluation of persons suspected of having a psychotic disorder requires a good history and a physical examination by a physician. Generally, non-organic disorders present with disturbances in thought and emotion, while organic disorders tend to present with mental clouding, confusion, and disorientation because of some degree of delirium. This is not a hard and fast rule, and in practice, there are many exceptions. The following are some characteristics that suggest the presence of an organic disorder:

1. No personal or family history of mental illness. Someone who presents with Schizophrenia-like psychotic symptoms will undoubtedly have some family or personal history of psychiatric treatment. This is particularly true if the subject is well into adulthood. First time psychotic breaks usually occur in early adulthood (early 20s for men, late 20s for women). The lack of history makes it more likely that there is some organic factor operating.

2. There is a history of serious medical illness with periodic relapses. This suggests organic etiology, especially if the subject is an elderly person.

3. There is very rapid onset. If the onset is in a few hours or days, this is a strong indicator of organic etiology. With symptoms that are not organically based, family members usually report some period of time that the client is acting "strange".

4. The client present with significant memory loss, confusion, disorientation, and clouding of consciousness (that may fluctuate rapidly - within hours).

Major Depressive Disorder and Bipolar (I and II) Disorder may have psychotic symptoms that are secondary to affective symptoms. Affective disturbance always precedes psychosis in these cases. Individuals with severe personality disorders may have brief periods of psychosis, especially at times of severe stress. Psychotic symptoms usually resolve when the environmental stressors are stabilized, either through direct psychosocial intervention or by removing the individual from the environment and placing him/or her into a stable and safe environment such as a hospital setting. Individuals with Autism Spectrum Disorder may also have psychotic symptoms. Again, these symptoms appear to be secondary to the developmental impairment.