What are hallucinations?
A hallucination is an experience of something that is not really there. It can involve any or all of the senses.
Visual hallucinations (seeing things that aren't there) are the most common type experienced by people with dementia. They can be simple (for example, seeing flashing lights) or complex (for example, seeing animals, people or strange situations).
People with dementia are often thought to be hallucinating when in fact they are simply mistaken about what they have seen (see Misperceptions and misidentifications, and dementia ).
What causes hallucinations?
Visual hallucinations are usually caused by damage to the brain. They are more common in people with dementia with Lewy bodies and Parkinson’s disease dementia. People with Alzheimer’s disease can also have hallucinations.
Hallucinations can also be caused by physical illness including fever, seizure, stroke, migraine and infection. Diseases that cause inflammation and infection, such as pneumonia, can interfere with brain function and cause delirium. Some people with delirium will have hallucinations. Delirium is a medical emergency.
Hallucinations are a rare side effect of many medications. The drugs for Parkinson’s disease can often trigger hallucinations. Speak to your GP before making any changes to medication.
Some people with worsening vision start to see things that aren’t there (visual hallucinations) because of their deteriorating sight and not from any other condition, such as dementia or a mental health problem. This is called Charles Bonnet syndrome.
