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

Sensory hallucinations

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.

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

Review Date: 02/22/2010
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.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)