Causes of Psychosis

The causes of psychosis can be grouped into three general categories: medical conditions — Psychotic symptoms can develop following a head injury (trauma) or any physical illness that disrupts brain functioning, such as encephalitis (brain inflammation), AIDS, or a brain tumor. Other symptoms, such as memory problems or confusion, are generally present as well.

Medical Conditions that cause Psychosis include:

• epilepsy
• tumors
• AIDS
• B12 deficiency carbon monoxide poisoning
• trauma
• heavy metal poisoning
• herpes
• Huntington’s disease
• syphili
• encephalitis

Substances

Use of, or withdrawal from, alcohol and drugs can be associated with psychotic symptoms. In many cases, these symptoms diminish as intoxication abates. In other cases, the patient may experience residual psychotic symptoms. As a summary substances that may cause schizophrenia are:

• amphetamines
• hallucinogens
• alcohol
• barbiturate withdrawal
• cocaine
• phencyclidine (PCP)

Psychiatric Disorders

Psychiatric disorders that may cause psychosis include, but are not limited to, schizophrenia, schizophreniform disorder, schizoaffective disorder, delusional disorder, and bipolar (manic-depressive) disorder. In addition, psychosis may occur in Alzheimer’s disease, Parkinson’s disease, and Tourette’s disorder. As a summary psychiatric disorders that may cause schizophrenia are:

• schizophreniform and schizoaffective disorders
• brief psychotic disorder
• delusional disorder
• mood disorders (e.g., bipolar disorder)
• Alzheimer's disease
• Parkinson's disease
• Tourette's disorder

In discussing psychosis in schizophrenia, the DSM-IV-TR notes that although psychosis can be narrowly defined as delusions or prominent hallucinations that the individual may or may not realize are hallucinatory experiences, psychosis can be more broadly defined as including positive symptoms, but not negative symptoms.