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Hallucinations

Definition

Hallucinations involve sensing things while awake that appear to be real, but instead have been created by the mind.

Alternative Names

Sensory hallucinations

Considerations

Common hallucinations include:

  • Feeling bodily sensations, such as a crawling feeling on the skin or the movement of internal organs
  • Hearing sounds, such as music, footsteps, windows or doors banging
  • Hearing voices when no one has spoken (the most common type of hallucination). These voices may be critical, complimentary, neutral, or may command someone to do something that may cause harm to themselves or to others.
  • Seeing patterns, lights, beings, or objects that aren't there
  • Smelling a foul or pleasant odor

In some cases, hallucinations may be normal. For example, hearing the voice of, or briefly seeing, a loved one who has recently died can be a part of the grieving process.

Causes

There are many causes of hallucinations, including:

  • Being drunk or high, or coming down from such drugs as marijuana, LSD, cocaine (including crack), PCP, amphetamines, heroin, ketamine, and alcohol
  • Delirium or dementia (visual hallucinations are most common)
  • Epilepsy that involves a part of the brain called the temporal lobe (odor hallucinations are most common)
  • Fever, especially in children and the elderly
  • Narcolepsy
  • Psychiatric disorders, such as schizophrenia and psychotic depression
  • Sensory problem, such as blindness or deafness
  • Severe illness, including liver failure, kidney failure, AIDS, and brain cancer

When to Contact a Medical Professional

A person who begins to hallucinate and is detached from reality should get checked by a health care professional right away. Many medical and psychiatric conditions that can cause hallucinations may quickly become emergencies.

A person who begins to hallucinate may become nervous, paranoid, and frightened, and should not be left alone.

Call your health care provider, go to the emergency room, or call the local emergency number (such as 911) if someone appears to be hallucinating and is unable to tell hallucinations from reality.

What to Expect at Your Office Visit

Your health care provider will do a physical examination and take a medical history. Blood may be drawn for testing.

Medical history questions may include the following:

  • How long have the hallucinations been occurring?
  • Do the hallucinations occur just before or just after sleep?
  • Has there been a recent death or other emotional event?
  • What medications are being taken?
  • Has alcohol been used?
  • Are illegal drugs being used?
  • Is there agitation?
  • Is there confusion?
  • Is there a fever?
  • Is there a headache?
  • Is there vomiting?

References

Freudenriech O, Weiss AP, Goff DC. Psychosis and schizophrenia. In: Stern TA, Rosenbaum JF, Fava M, Biederman J, Rauch SL, eds. Massachusetts General Hospital Comprehensive Clinical Psychiatry. 1st ed. Philadelphia, Pa: Mosby Elsevier; 2008:chap 28.

Review Date: 2/22/2010
Reviewed By: David B. Merrill, MD, Assistant Clinical Professor of Psychiatry, Department of Psychiatry, Columbia University Medical Center, New York, NY. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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