It is estimated that about 50% of people with Parkinson’s will, at some point, experience hallucinations. In a recent study in London1, in which investigators used a specially developed screening tool, they found that as many as 75% experienced hallucinations. The presence of hallucinations is also sometimes used to differentiate Parkinson’s from other conditions such as atypical parkinsonism2.
They can affect younger people but are more often associated with those who are older and have had Parkinson’s for some time.
It is thought that Parkinson’s itself can be a cause of hallucinations, although other doctors argue that they are simply a side effect of certain medications used to treat the disease. But other factors may also be involved:
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Underlying illness
Hallucinations sometimes occur as a result of other illnesses such as a chest or bladder infection or as a side effect of the medications used to treat them.
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Medication
Hallucinations can occur as a side effect of many medications, but are particularly associated with the amantadine, dopamine agonists or anticholinergics groups, especially in older people. Sometimes they occur when medications have been adjusted or if a new medication is added. However hallucinations may occur at any time and there may not appear to be any correlation with a change in drug regime.
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Memory problems
Hallucinations are more common in those who already have some memory problems and are often associated with dementia. For further information on memory problems and dementia see dementia.
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Sleep disturbance
Those whose normal sleep/wake pattern is disturbed or who sleep a lot during the day seem to be more prone to hallucinations and some may also experience sleep talking or sleep walking.
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Eyesight
Visual hallucinations can occasionally occur because of poor eyesight.
