Hallucinations: What Causes Them?

"Hallucinations are unreal sensory experiences, such as hearing or seeing something that is not there. Any of our five senses (vision, hearing, taste, smell, touch) can be involved. Most often, when we learn someone is hallucinating, we think about psychosis, such as schizophrenia. Hallucinations can also occur in people who have bipolar disorder with psychosis or major depressive disorder with psychosis."

"One fascinating cause of visual hallucinations can occur when someone has a severe disease of both retinas in their eyes. For example, there was a patient who had a viral infection in each of his retinas. He reported seeing tiny people and small animals playing and running around his hospital room. Of course, he was having a visual hallucination. The virus stimulated his retinas, which sent signals to the occipital lobe in the back of his brain, where vision processing occurs."

"While these mental disorders are common causes of hallucinations, there are numerous general medical causes as well. For example, people with a variety of neurological illnesses may hallucinate. Those illnesses include migraine headaches, Parkinsonism, some dementias, delirium, brain tumors, and others. Brain tumors in the frontal lobe often present with a personality change. Another early symptom can be hallucinations of smelling burnt rubber. This is a good example of a hallucination related to the sense of smell."

Hallucinations are unreal sensory experiences that can involve vision, hearing, taste, smell, or touch. Psychotic illnesses such as schizophrenia, bipolar disorder with psychosis, and major depressive disorder with psychosis commonly cause hallucinations. Numerous general medical and neurological conditions can also produce hallucinations, including migraines, Parkinsonism, dementias, delirium, and brain tumors. Frontal lobe tumors may cause personality change and olfactory hallucinations like smelling burnt rubber. Severe retinal disease can elicit visual hallucinations by sending abnormal signals to the occipital lobe. New-onset hallucinations warrant timely physician evaluation; children and teenagers may have normal or disorder-related hallucinations.

Read at Psychology Today