Hallucinations: Dementia and mental health conditions

Hallucinations happen when abnormal changes in the brain make someone see, hear or even smell things that aren’t really there, such as dementia or psychosis. The person may know they are hallucinating, or believe their experience exists in reality, not just their own mind. Either way, hallucinations can be extremely distressing.

A hallucination is not the same as a delusion. A delusion is a belief that is not based in reality, while a hallucination is an imagined sensory experience. For example, a hallucination would be someone seeing and speaking to their son who wasn’t there, while a delusion would be believing their son visits them regularly when he actually never does.

Both hallucinations and delusions are symptoms of psychosis, a state in which a person loses their grasp of reality.

People can experience multiple types of hallucinations.

Types of hallucinations in dementia and mental health conditions

Visual hallucinations

Visual hallucinations are when you see things that aren’t there, or a distorted version of what’s really there.

Visual hallucinations can be simple, such as seeing lights or an object for a brief moment, to complex scenarios like talking to a room full of people who aren’t really there.

There is a very rare condition called Alice in Wonderland syndrome, that can make people see objects and people around them as larger or smaller than they really are. Echoing Alice’s growing and shrinking, the person can feel that they are larger or smaller than they are because of how they perceive their surroundings. They can even experience the feeling of their body growing and shrinking.

Another example of specifically visual hallucinations is that of Charles Bonnet syndrome. This is moderately common in people who are losing their sight, when the brain compensates for the lack of information from the eyes by creating hallucinations.

Auditory hallucinations

These are hallucinations that a person hears. It could be anything, from thinking music is playing to believing someone is knocking on their door to hearing voices.

Auditory hallucinations can happen in alcoholics, who can develop alcoholic hallucinosis after a heavy drinking session or during withdrawal.

Olfactory hallucinations

Olfactory hallucinations are illusions of smell. These can be good or bad odours, or more worrying ones like believing there is a gas leak or that something is burning.

Also called phantosmia, these hallucinations were reported as a symptom of around 6% of people with Covid-19.

Gustatory hallucinations

Hallucinations of taste, these can come on randomly or while eating. A person could believe what they are eating is burnt or rotten when it isn’t, or have tastes appear at random when they are not eating.

Tactile or Somatic hallucinations

Hallucinations to do with physical touch, either externally or internally. The person may experience pleasant feelings, like being kissed, or more unnerving ones like itching, burning or having insects crawling on them. 

They may feel like things are moving around inside them or even pain due to something that’s not real, like a phantom wound.

Extreme forms of these can make somebody experience severe pain due to an injury that does not exist, from feeling as if they are being disembowelled or strangled to having had a limb amputated.

Hypnagogic and Hypnopompic hallucinations

Hypnagogic and hypnopompic describe hallucinations that occur when you are falling asleep and waking up, respectively. It’s not the same as dreaming. You might see, hear, smell, taste or feel something externally while in that strange twilight zone between being awake and asleep.

A fairly common example is seeing things while experiencing sleep paralysis. Sometimes your mind wakes up slightly before your body and you can’t move. Most people experience this a few times in their lives, and some report seeing or hearing things in their room but being powerless to speak or move. One of the more disturbing visions is that of the night hag. For hundreds of years, people have reported feeling or seeing a demon during sleep paralysis; sometimes it is even sat on their chest, restricting their breathing.

What causes hallucinations?

Dementia and hallucinations

Hallucinating can be a symptom of dementia, particularly dementia with Lewy bodies and Alzheimer’s disease.

Dementia damages parts of the brain, which are each responsible for different functions. When the damage is done to areas that regulate and interpret sensory perception, visuospatial awareness or messaging between areas of the brain, the person may experience hallucinations.

These hallucinations can be extreme, and can be worse when the person is in an unfamiliar environment or not following their usual routine.

As with confabulation (when the brain creates false memories), the person may really believe that their experience is real, and it is often best to validate their feelings around the hallucination, rather than confuse them more but telling them it’s not real.

Other damage to the brain

Any damage to the brain can disrupt its ability to function normally and lead to hallucinations. Causes could include:

• Neurological conditions
• Brain tumours
• Epilepsy and seizures
• Stroke

Some short-term states can affect brain function and cause hallucinations, including:

• Infection
• Fever
• Delirium, often from dehydration or lack of sleep
• Migraine

Mental health issue

Some mental health issues can cause people to hallucinate, particularly hearing voices.

Some mental health issues that can cause hallucinations include:

• Schizophrenia
• Schizoaffective disorder
• Bipolar disorder
• Personality disorders

In people with mental health issues, hallucinations are often accompanied by delusions. These beliefs have little to no basis in reality and can include beliefs that:

• They are physically ill
• Certain people are out to get them or trying to steal money/their job/their partner from them
• Their partner is cheating on them
• They are of superior intelligence, others are jealous of them and other grandiose beliefs of their own importance
• That everybody hates them
• Somebody they have or have not met is in love with them (erotomania)

Drugs and alcohol

Excessive alcohol use can lead to alcoholic hallucinosis or alcohol-induced psychosis, which can become an ongoing condition called alcohol-induced psychotic disorder, if the drinking continues.

Alcohol can have a devastating effect on the brain, from short-term loss of memory and inhibitions to long-term complications, such as Wernicke-Korsakoff syndrome, or alcohol-induced dementia. The hallucinations don’t just happen when the person is drinking. They can happen when they are sober or even as part of withdrawal symptoms.

Overuse of alcohol, some medications and recreational drugs, particularly hallucinogens like acid, ecstasy and weed, change the chemicals in the brain (and damage it over time) causing delusions and hallucinations.

This may be the intention when taking it, especially in the case of someone taking LSD, but a ‘bad trip’ can be a terrifying experience and even cause someone to harm themselves or others due to their hallucinations.

How can hallucinations be treated?

Hallucinations are usually treatable by treating the underlying cause. Treatment could include:

• Medications, such as antipsychotic medications
• Support with alcoholism or drug addiction
• In the case of Wernicke-Korsakoff syndrome, thiamine supplements can stop hallucinations
• Addressing the cause of delirium, such as rehydration or sleep
• Mental health programmes with treatments such as counselling, mindfulness and cognitive behavioural therapy
• Neurorehabilitation

Treating hallucinations in a person living with dementia

Hallucinations in dementia are more complicated to teas dementia is a progressive illness with no current cure. If you have a loved one who is living with dementia and hallucinations, you should still see a GP. It may just be that the hallucinations are due to something like dehydration or lack of sleep, as dementia makes it harder for a person to look after themselves. The doctor investigate further.