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    People with dementia are prone to hallucinations, delusions, and psychosis. Not everyone will have these symptoms, but they can be very distressing for the person with dementia and those who care for them. Poor short-term memory and perceptual abnormalities changes the way a person with dementia understands the world. This makes it difficult for them to interpret other people’s behaviour and harmless events.

    This can be troubling to those around the person with dementia when they interpret things in a way that seems unreasonable. They might forget where they put an item and when it can’t be found they believe it was stolen. Or they may think a spouse is being unfaithful because they don’t know where they are, making them feel insecure and worried they are no longer loved because of their dementia.

    Sometimes people with dementia cannot recognise themselves in the mirror and think there is a stranger in the house. In this case memory deficits have made them forget their age, so when they look in the mirror, they expect to see a younger person looking back at them.

    A billowing curtain, a barking dog, or headlights coming into a room could all be mistaken for something else. These are common occurrences but a person with cognitive impairment might explain them differently: a ghost, a call for help, or a burglar shining a light through the window.

    Usually, people can be reassured with an explanation however, it is important to realise that there may be a logical explanation for their actions.

    Although these symptoms might be considered psychosis since the person seems out of contact with reality, it is misunderstanding and misinterpreting. The term psychosis refers specifically to delusions and hallucinations.

    Delusions and hallucinations occur in a variety of brain diseases, including dementia. A delusion is an unshakeably held false belief. If no amount of evidence will convince the person that they are mistaken, then it is a delusion. A hallucination is a sensory perception without an obvious external cause. So, if a person can see, hear, smell, feel or taste something that doesn’t appear to be there then it is usually a hallucination.

    Who gets psychotic symptoms in dementia?

    Alzheimer’s Disease

    Up to 70% of people with Alzheimer’s disease can get psychotic symptoms. They usually occur in the moderate to severe stage and may take the form of paranoia (thinking someone is trying to harm them), or other delusions.

    Lewy Body Dementia

    Up to 80% of people with Lewy Body dementia develop psychotic symptoms. Visual hallucinations are very common, such as seeing images of little people or children. They may also have hallucinations with other senses like hearing voices. The reaction to these experiences can range from mild interest to extreme anger – becoming agitated and chasing “people” away with a weapon.

    Parkinson’s Dementia

    People with Parkinson’s disease can experience delusions and hallucinations. These symptoms are often aggravated by the medication for Parkinson’s disease, so it is very important to have medications reviewed and, whenever possible, reduced. This can increase physical problems and so striking a balance between treating mobility issues and maintaining a normal mental state is important.

    Vascular dementia

    Psychosis can occur in vascular dementia depending on the area of the brain that has been damaged.

    People with pre-existing mental illness

    People with schizophrenia or bipolar disorder already have symptoms of psychosis. These often persist if the person develops dementia.


    This is sudden confusion with a physical cause, such as infection, illness, effects of medication, dehydration, or alcohol withdrawal. Delirium can make a person disorientated, suspicious (delusional) and prone to visual hallucinations. They may imagine insects are crawling on an arm or leg and try to pick them off. They might get frightened by shadows or lights and misinterpret them as threatening. The symptoms of delirium fluctuate during the day and night so hallucinations can be temporary. They may disappear for a while, only to reappear later.

    Do these symptoms matter?

    Misunderstandings, misinterpretations, and psychosis can be very frightening to witness and cause a person with dementia to act unpredictably. These symptoms are a sign that things are not right, especially if they come on suddenly. It could show they have developed a delirium on top of dementia.

    However, not all psychotic symptoms are distressing. For example, seeing a deceased relative sitting on a chair nearby might be comforting. In some cultural groups it is normal to see or hear deceased people and in this case the person wouldn’t need treatment.

    What to do about psychosis

    Be patient, reassure, and offer support and positive reinforcement. If the person is not distressed or responding in a way that is risky, then do nothing.

    Check the facts

    What seems to be a delusion or misunderstanding might be real. It is entirely possible that someone is trying to take advantage of or harm a person with dementia. This possibility needs to be taken into consideration.

    Check hearing and visual aids

    It may be helpful to check that hearing aids are working effectively. People can misunderstand what they have only partially heard and develop false ideas about what others are saying. Similarly, cleaning glasses or updating the prescription may help to prevent people from misinterpreting objects within the environment.

    Check-up with GP

    This might reveal a treatable condition, such as a urinary tract infection, constipation, or pain that could have caused delirium.

    Review medications

    As previously noted, Parkinson’s medication can cause or worsen psychosis. Other medications like morphine, a painkiller, and digoxin, for heart disease, can also cause hallucinations.

    Medication can reduce symptoms or calm people, so they are less distressed. However, antipsychotic medications can have serious side-effects and they should not be given to people with Lewy Body or Parkinson’s dementia. For people with other conditions that cause dementia, antipsychotics should only be used as a last resort. If they are necessary, a minimal dose should be trialled for a short time before being reviewed to make sure they are effective.

    Check their environment

    If there are obvious triggers, for instance, car lights flashing in the bedroom, then try shifting the bed, hang heavier curtains, or blackout lining. Cover reflecting surfaces such as mirrors. Improve the lighting, including having night lights, and reduce outside noise. Talk to others who might have their own ingenious solutions. Experiment.

    Be patient

    Remember that the experience is real for the person with dementia. They might accept that you have asked “people” to leave or chased them away, but the chances are the unwanted visitor (hallucination) will return.

    Be methodical and know where they like to put things for safekeeping so that if they argue that something has been stolen, then you can help to find it.

    Record when the psychotic symptoms are most common and try to distract them by doing something meaningful at that time of day (e.g., go for a walk).

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