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Characteristics, Causes and symptoms, Diagnosis, Treatment, Prognosis

A symptom of mental illness characterized by a radical change in personality and a distorted or diminished sense of objective reality.


Psychosis may appear as a symptom of a number of mental disorders, including mood and personality disorders, schizophrenia, delusional disorder, and substance abuse. It is also the defining feature of the psychotic disorders (i.e., brief psychotic disorder, shared psychotic disorder, psychotic disorder due to a general medical condition, and substance-induced psychotic disorder).

Patients suffering from psychosis are unable to distinguish the real from the unreal. They experience hallucinations and/or delusions that they believe are real, and they typically behave in an inappropriate and confused manner.

Causes and symptoms

Psychosis may be caused by a number of biological and social factors, depending on the disorder underlying the symptom. Trauma and stress can induce a short-term psychosis known as brief psychotic disorder. This psychotic episode, which lasts a month or less, can be brought on by the stress of major life-changing events (e.g., death of a close friend or family member, natural disaster, traumatic event), and can occur in patients with no prior history of mental illness.

Psychosis can also occur as a result of an organic medical condition (known as psychotic disorder due to a general medical condition). Neurological conditions (e.g., epilepsy, migraines, Parkinson's disease, cerebrovascular disease, dementia), metabolic imbalances (hypoglycemia), endocrine disorders (hyper- and hypothyroidism), renal disease, electrolyte imbalance, and autoimmune disorders may all trigger psychotic episodes.

Hallucinogenics, PCP, amphetamines, cocaine, marijuana, and alcohol may cause a psychotic reaction during use, abuse, or withdrawal. Certain prescription medications such as anesthetics, anticonvulsants, chemotherapeutic agents, and antiparkinsonian medications may also induce psychotic symptoms as a side-effect. In addition, toxic substances like carbon dioxide and carbon monoxide, which may be deliberately or accidentally ingested, have been reported to cause substance-induced psychotic disorder.

Schizophrenia and its related disorders (schizophreniform disorder and schizoaffective disorder), mental illnesses with strong psychotic features, are thought to be caused by abnormalities in the structure and chemistry of the brain and influenced by both social and genetic factors. Delusional disorder, another mental illness defined by psychotic episodes, is also thought to have a possible hereditary and neurological base. Abnormalities in the limbic system, the portion of the brain on the inner edge of the cerebral cortex that is believed to regulate emotions, are suspected to cause the delusions that are a feature of psychosis.

Psychosis is characterized by the following symptoms:

  • Delusions. An unshakable and irrational belief in something untrue. Delusions defy normal reasoning, and remain firm even when overwhelming proof is presented to disprove them.
  • Hallucinations. Psychosis causes false or distorted sensory experience that appear to be real. Psychotic patients often see, hear, smell, taste, or feel things that aren't there.
  • Disorganized speech. Psychotic patients often speak incoherently, using noises instead of words and "talking" in unintelligible speech patterns.
  • Disorganized or catatonic behavior. Behavior that is completely inappropriate to the situation or environment. Catatonic patients have either a complete lack of or inappropriate excess of motor activity. They can be completely rigid and unable to move (vegetative), or in constant motion. Disorganized behavior is unpredictable and inappropriate for a situation (e.g., screaming obscenities in the middle of class).


Patients with psychotic symptoms should undergo a thorough physical examination and detailed patient history to rule out organic causes of the psychosis (such as brain tumor). If a psychiatric cause is suspected, a psychologist or psychiatrist will usually conduct an interview with the patient and administer clinical assessments. These assessments may include the Adolescent Behavior Checklist (ABC), Anxiety Disorders Interview Schedule for DSM-IV (ADIS-IV), Psychotic Behavior Rating Scale (PBRS), and the Chapman Psychosis Proneness Scales.


Psychosis caused by schizophrenia or another mental illness should be treated by a psychiatrist and/or psychologist. Other medical and mental health professionals may be part of the treatment team, depending on the severity of the psychosis and the needs of the patient. Medication and/or psychosocial therapy is typically employed to treat the underlying disorder.

Antipsychotic medications commonly prescribed to treat psychosis include risperidone (Risperdal), thioridazine (Mellaril), halperidol (Haldol), chlorpromazine (Thorazine), clozapine (Clozaril), loxapine (Loxitane), molindone hydrochloride (Moban), thiothixene (Navane), and olanzapine (Zyprexa). Possible common side-effects of antipsychotics include dry mouth, drowsiness, muscle stiffness, and hypotension. More serious side effects include tardive dyskinesia (involuntary movements of the body) and neuroleptic malignant syndrome (NMS), a potentially fatal condition characterized by muscle rigidity, altered mental status, and irregular pulse and blood pressure.

Once an acute psychotic episode has subsided, psychosocial therapy and living and vocational skills training may be recommended. Drug maintenance treatment is usually prescribed to prevent further episodes.


The longer and more severe a psychotic episode, the poorer the prognosis for the patient. However, early diagnosis and long-term follow-up care can improve the outcome for patients with psychotic disorders. Schizophrenia has a 60% treatment success rate.

See also Neurosis

Paula Ford-Martin

Further Reading

American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders 4th ed. Washington, D.C.: American Psychiatric Press, Inc., 1994.

Further Information

National Alliance for the Mentally Ill (NAMI). 200 North Glebe Road, Suite 1015, Arlington, VA, USA. 22203-3754, (800)950-6264. http://www.nami.org.

National Institute of Mental Health (NIMH). 6001 Executive Boulevard, Rm. 8184, MSC 9663, Bethesda, MD, USA. 20892-9663, fax: (301)443-4279, (301)443-4513. Email: nimhinfo@nih.gov. http://www.nimh.nih.gov.

Additional topics

Psychology EncyclopediaDiseases, Disorders & Mental Conditions