What causes hallucinations?

Visual hallucinations are usually caused by damage to the brain, and they are more common in people with dementia with Lewy bodies and Parkinson’s disease dementia. However, those with Alzheimer’s disease can also have hallucinations.

Hallucinations can 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, which is a medical emergency.. Some people with delirium will have hallucinations.

Hallucinations are also a rare side effect of many medications. Medications for Parkinson’s disease can often trigger hallucinations. It is important to speak to your General Practitioner before making any changes to medication.

Some 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.

How does a person experience hallucinations?

Some people with dementia will have hallucinations in different senses – for example:

• auditory hallucinations – hearing things that aren’t there, like voices or footsteps
• olfactory hallucinations – smelling things that aren’t there, such as smoke or perfume
• tactile hallucinations – physically feeling things that aren’t there, such as being kissed or insects crawling over their skin
• gustatory hallucinations – tasting things that aren’t there, such as a metallic taste in their mouth.

Visual hallucinations are more common in people with dementia with Lewy bodies, and often take the form of complex, vivid and very realistic hallucinations of people or animals. They often last for several minutes and happen often.

Hallucinations can be extremely distressing, and can lead to the person with dementia becoming frightened and in need of support. However, some people find the hallucinations pleasant or comforting. It often depends on what they are hallucinating and how others respond.

How can you tell if someone is hallucinating?

Sometimes the person may appear to be hallucinating, but there is another cause (for example, it is a misperception instead). The following tips can help to identify hallucinations:

• Hallucinations differ from misperceptions or misidentifications. Listen to what the person is describing, and check if anything could be causing what they are experiencing. For example, if they describe a ‘swarm of insects’, and there is a busy pattern on a carpet, it may be a misperception. By changing or covering the carpet, the misperception may stop.
• If the person seems to be having auditory hallucinations (hearing things that aren’t there), arrange to have their hearing checked. If the person wears a hearing aid, check that it is working properly at the right setting, and encourage them to wear it. The person may be having problems with their hearing, rather than hallucinating.
• If the person seems to be having gustatory hallucinations (tasting things that aren’t there), make sure they are getting regular dental check-ups to rule out other causes such as tooth decay or denture cream.

Supporting a person who is experiencing hallucinations

If the person you care for regularly hallucinates, make an appointment for them to see their GP (General Practitioner).

Make sure the person has regular medication reviews with a pharmacist or GP as new medications, or the combination of their medications, can be a cause of hallucinations.

When a person is hallucinating, how you respond has a big impact on their experience and wellbeing. If a person is hallucinating, try the following tips.

• If the person’s hallucinations involve multiple senses, seek medical help immediately, as this can be a sign of serious illness. You should seek medical attention if:
  • the hallucinations frighten the person
  • the hallucinations last a long time
  • the hallucinations happen often
  • the person seems more confused than usual
• Calmly explain what is happening. If they cannot retain this information, repeat it when they are more relaxed. If this is still not possible, don’t argue with them – it will not help. Trying to convince someone that they are mistaken can lead to more distress.
• Stay with the person and try to reassure them. Ask them to describe their hallucination.
• Hallucinations may be limited to a particular setting. Gently leading someone away from where they are having the hallucinations can help make them disappear.
• Check that the person is not hungry, thirsty or uncomfortable. Dehydration, constipation or infection can lead to delirium, a cause of hallucinations.
• It may help to distract the person and see if this stops the hallucinations.

People are less likely to hear voices that are not there when they are talking to someone real. Having company may help.

Seeing the GP for hallucinations

When seeing the GP for support with hallucinations, it will help to bring details of:

• what the person saw or sensed
• what time of day it happened, and after what event (for example a nap, meal, or exercise)
• where it happened, and how long it lasted
• how the person responded (for example, if they were distressed) and the words they used to describe what they experienced
• any medication the person is taking and the dosage (including any over-the-counter medications)
• key details of the person’s medical history, including any long-term health conditions, previous conditions and mental health issues
• the person’s use of alcohol or other recreational drugs.

Content provided by Alzheimer’s Society