psychosis

What Are the Causes of Hallucinations?

Paul Ballas Health Guide January 23, 2007
  • I have started taking medication to control my hallucinations and the drugs are making me tired. Is there another way for me to control my hallucinations?

    This seemingly straightforward question is actually fairly complicated. It gives me the opportunity to discuss hallucinations from several disorders. I have treated many patients who have been hallucinating and a lot of them do not have schizophrenia. About 1% of the population has the psychiatric disorder schizophrenia, but 10 – 27% of the general population have experienced at least one hallucination, usually visual hallucinations. Obviously most of these are not due to schizophrenia. Usually they are due to the use of a substance like alcohol or cocaine or they are caused by a depressive disorder. Many people also experience mild hallucinations as they wake up or as they go to sleep, so called hypnopompic and hypnagogic hallucinations respectively. Sometimes these particular phenomenon suggest the presence of the sleep disorder narcolepsy.

    Hallucinations are experienced in many neurologic and psychiatric disorders other than schizophrenia. One example that isn’t often discussed is that about half of people who have migraines experience migrainous hallucinations. These are usually visual hallucinations of geometrical patterns but in rare cases a person may also have the experience of seeing objects which appear much larger or smaller than they really are. This phenomenon is sometimes known as Alice in Wonderland Syndrome, named after the famous author Lewis Carroll who had these symptoms and wrote detailed and beautiful descriptions of these phenomenon in his fiction. Visual hallucinations are also experienced as a side effect of certain illicit substances like mescaline and LSD. Patients who experience delirium often have hallucinations that resolve with the treatment of the cause of the delirium. Common causes of delirium include infections and reactions to prescription medications.

    Schizophrenia is classically associated with auditory hallucinations. These are found in 60 – 90% of people with schizophrenia, but are also present in many other disorders. For example, 20% of patients in the manic phase of bipolar disorder and almost 10% of patients with major depressive disorder experience auditory hallucinations. These disorders are managed primarily with medications, usually antipsychotic medications in psychotic depression and schizophrenia, and also with mood stabilizers in bipolar disorder. Electroconvulsive therapy has also been shown to be effective in reducing or eliminating hallucinations in these disorders. Typically it is only used once several medications have been tried unsuccessfully.

    As this blog has hopefully shown, there are a wide range of causes for hallucinations and it is important for patients’ physicians to make sure they are not caused by something other than schizophrenia, like a medication, infection, or metabolic abnormality. A future blog can explore these causes of hallucinations in greater detail.