Hallucinations

Hallucinations happen when someone sees, hears, smells, tastes or feels things that don't exist outside their mind. They are common in people with schizophrenia, and are usually experienced as hearing voices.

Hallucinations can be frightening as they may be unexpected or unwanted, but there's usually an identifiable cause. They can occur as a result of:

• taking illicit drugs or alcohol
• a mental illness such as schizophrenia or dementia
• a progressive neurological condition such as Alzheimer's disease or Parkinson's disease
• loss of vision caused by a condition such as macular degeneration – this is known as Charles Bonnet syndrome

If you have hallucinations and are worried about them, see your GP straight away. If necessary, call 999 as you may have a serious mental health condition.

Hallucinations can make you feel nervous, paranoid and frightened, and it's important to be with someone you can trust.

In the meantime, the following information explains the typical types of hallucinations, including why they occur and what you can do. It covers:

• hearing voices 
• drug-induced hallucinations 
• hallucinations and sleep 
• hallucinations experienced by children with a fever
• Charles Bonnet syndrome

Hallucinations can also occur as a result of extreme tiredness or recent bereavement. However, these and other rarer causes are not covered here.

Hearing voices 

Hearing voices in the mind is the most common type of hallucination in people with conditions such as schizophrenia. The voices can be critical, complimentary or neutral, and may give out potentially harmful commands or even engage the person in conversation. They may make a running commentary on the person's actions.

Hearing voices is a well-recognised symptom of schizophrenia, dementia or bipolar disorder, but can be unrelated to mental illness.

The experience is usually very distressing, but it is not always negative. Some people who hear voices are able to live with them and get used to them or may consider them a part of their life. 

It is not uncommon for recently bereaved people to hear voices, and this may sometimes be the voice of their loved one.

Practical advice

If you're hearing voices, discuss any concerns you have with your GP. They will refer you to a psychiatrist if necessary. This is important in determining whether you have a serious mental illness.

There is no shame in seeing a psychiatrist, and it's important to be thoroughly assessed and treated early. If your voices are due to schizophrenia, the earlier your treatment is started, the better the outcome.

You may also find the following advice helpful:

• Talk to other voice hearers. Try the Hearing Voices Network.
• Be open to discussing your voices.
• Try to understand where the voices come from and why, and what triggers them.

For more information and practical advice on dealing with voices in your mind, read the Mental Health Foundation's fact sheet on hearing voices.

Drug-induced hallucinations 

Illegal drugs and alcohol

People can experience hallucinations when they're high on illicit drugs such as amphetamines, cocaine, LSD or ecstasy. Hallucinations can also happen during withdrawal from alcohol or drugs if you suddenly stop taking them.

Drug-induced hallucinations are usually visual, but may affect other senses. Hallucinations include flashes of light or abstract shapes, or may even take the form of an animal or person. More often, visual distortions occur that alter the person's perception of the world around them. 

These hallucinations can happen on their own or they can occur as a part of drug-induced psychosis. After long-term use, they may cause schizophrenia. Read an account of a drug-induced psychotic breakdown.

Some people take cannabis to "calm themselves" and relieve their psychotic symptoms, without realising that in the longer term, the cannabis makes the psychosis worse.

Heavy use of alcohol can also lead to psychotic states, hallucinations and dementia.

Find out how to get help for a drug problem.

Medication

Various prescription medicines can occasionally cause hallucinations. Elderly people may be at particular risk.

Hallucinations caused by medications can be dose-related and usually go away when you stop taking the medicine. However, never stop taking medication without speaking to your doctor first, and if necessary after being assessed by a psychiatrist.

Speak to your GP about how the medication is affecting you, so you can discuss the possibility of switching to another medicine. 

Hallucinations and sleep 

It is relatively common for people to have hallucinations just as they're falling asleep (hypnagogic), or as they start to wake from sleep (hypnopompic). 

You may hallucinate sounds or see things that don't exist, such as moving objects or even a formed image such as a person (people may think they've seen a ghost).

Hypnagogic and hypnopompic hallucinations are especially common in people with the sleep disorder narcolepsy, although they are also common in people without this or any disorder. They are essentially like dreams, and in themselves are nothing to worry about.

Hallucinations in children with a fever 

Hallucinations can sometimes occur in children who are ill with a fever. If your child is unwell with a body temperature of over 37.5C (99.5F) and you think they are hallucinating, call your GP.

In the meantime, stay calm, keep your child cool and reassure them. Encourage them to drink plenty of fluids and give them paracetamol or ibuprofen (always read the patient information leaflet to find out the correct dose and frequency for your child’s age, and check they are not allergic to medicines you give). The hallucinations should pass after a few minutes.

For more information, read about fever in children.

Charles Bonnet syndrome

It is estimated that around 60% of people with severe visual impairment may experience temporary visual hallucinations.

This is known as Charles Bonnet syndrome and tends to affect older people who have lost their sight, but can affect people of any age. 

The hallucinations usually last for around 12-18 months and can take the form of simple patterns or detailed images.

Some of the most common causes of visual impairment include:

• age-related macular degeneration (AMD) – where the central part of the back of the eye (the macula, which plays an important role in central vision) stops working properly
• cataracts – where cloudy patches can form within the lenses of the eyes
• glaucoma – where fluid builds up inside the eye, damaging the optic nerve (which relays information from the eye to the brain)
• diabetic retinopathy – where blood vessels that supply the eye become damaged from a build-up of glucose

Around 100,000 people in the UK are thought to be affected by Charles Bonnet syndrome.