A stroke can sometimes lead to hallucinations or delusions, and may happen in up to one in 20 people.

Some symptoms can start soon after a stroke, but they can also start weeks or months later. It may be more common with certain types of stroke, but it can also happen alongside 'silent' strokes, which are due to very small blockages or bleeds in the brain without obvious physical symptoms. Hallucinations and delusions are also known as 'psychotic symptoms'. This can be due to mental health problems, but it can also be caused by a stroke. On this page:

What is a hallucination?
What is a delusion?
Causes of hallucinations and delusions after a stroke
What to do when someone becomes unwell
Types of hallucination after stroke
Types of delusion after stroke
Other reasons for problems with recognition and awareness
Getting help with hallucinations and delusions

What is a hallucination?

A hallucination is when you perceive something that isn't there. It can affect any of your senses. You may see things (visual hallucinations), or hear sounds or voices (auditory hallucinations). You can also smell, taste or feel things that are not there.

What is a delusion?

Delusions are strong beliefs about something that is untrue. For example, someone might think they are being spied on or that someone is trying to harm them.

Causes of hallucinations and delusions after a stroke

  • Damage to the brain.
  • Vision loss.

Other causes:

  • Other conditions of the brain, such as dementia, Parkinson's disease and brain tumours.
  • Serious infections such as malaria, and HIV and AIDS.
  • Alcohol or drug misuse.
  • Rare side-effect of some types of medication, or a medication overdose.

What to do when someone becomes unwell

If you or someone you care for starts having hallucinations or delusions, contact the GP as soon as possible. Getting early treatment can be more effective.

Types of hallucination after stroke

Due to vision loss (Charles Bonnet syndrome)

Visual hallucinations due to a loss of vision are also known as Charles Bonnet syndrome.

If you lose all or part of your field of vision after a stroke, the brain might generate images to fill in the missing areas. These types of hallucinations are usually temporary but may last for several months before reducing. The hallucinations can appear as simple patterns or complex images of people, places and objects.

There is no specific treatment for Charles Bonnet syndrome, but RNIB has information and advice about coping with the condition, as well as making the most of your vision. You can also read our information about vision problems after stroke.

Due to damage in the mid-brain (peduncular hallucinosis)

This is a type of visual hallucination that can occur when there is damage to the midbrain. These hallucinations often involve vivid, colourful scenes with animals, people and patterns. They may disappear within a few weeks, but sometimes carry on for longer.

Each hallucination may last for several minutes or up to several hours, and they often occur in the evening. Many people don't find the hallucinations worrying and realise they are not real.

Hearing sounds and voices (auditory hallucinations)

This can include hearing voices, which may seem to come from inside or outside your head. They could be friendly or critical. You might hear music or odd sounds. You might hear sounds along with a visual hallucination.

Tip: check vision and hearing

Sometimes a hearing problem can distort sounds, or hearing aids can make noises. Check if hearing aids are working well, and think about a hearing test.

Some eye conditions can cause problems like flashes of light, a halo effect or moving black spots. If you experience these types of vision changes, have an urgent eye test to look for any problems with your eyes or eyesight.

Other reasons for sensory disturbances

  • Seizures and epilepsy can cause visual disturbances, as well as changes to hearing and sensation. Read our guide to seizures after a stroke.
  • Migraine aura can also cause visual, sensory and balance disturbances. Read our guide to migraine and stroke.
  • Sensation changes after stroke include burning or cold sensations, and pins and needles. Read more in our guide to physical effects of stroke.
  • Changes to taste and smell after stroke include a smell of burning, or a metallic taste in your mouth. Read more in our guide to changes to taste and smell.

Types of delusion after stroke

  • Believing someone is trying to harm you (persecutory delusions).
  • Becoming very jealous of someone or something (delusional jealousy).
  • Believing you or someone else is an imposter (Capgras syndrome).
  • Thinking that there are two copies of a place, such as a room or house (reduplicative paramnesia).

Other reasons for problems with recognition and awareness

A stroke can affect your ability to recognise things, or find the right names for objects or people. To an observer, this could make it seem as if someone is imagining things, but the cause is damage to their cognitive or language skills.

Cognitive effects

Some types of changes to perception due to cognitive effects (problems with memory and thinking):

  • Problems with identifying things (agnosia).
  • Thinking that part of your body does not belong to you, or belongs to someone else (somatoparaphrenia).
  • Not being able to recognise faces (prosopagnosia).
  • Not being aware that you've been affected by a stroke, such as not realising you can't use your hand or can't walk (anosognosia).
  • Spatial neglect: not being aware of things to one side of your body.

You can read more about these changes to your perception in our guide to problems with memory and thinking.

Behaviour changes

People can sometimes behave out of character due to a stroke. They might become less inhibited, or they could lose interest in things they used to enjoy. You can read more in our guide to behaviour changes after stroke.

Emotional changes

The emotional impact of a stroke can lead to depression, which can change how someone acts. You can read more about the emotional effects of stroke.

Sudden confusion (delirium)

Particularly in older people, infections like a chest or bladder infection can make someone become suddenly confused (delirium). Other causes such as low blood sugar and head injury can also cause confusion. If this happens, seek medical help as soon as possible.

Getting help with hallucinations and delusions

Hearing sounds or seeing things that are not there can be upsetting and frightening. Tell your GP or a member of your stroke team. They can help you find out the cause of your symptoms and refer you for treatment and support.

Hallucinations and delusions usually become less intense over time. Medication or psychological treatment can help some people. Reassurance or self-help strategies can help a person living with the condition.

You can read more about psychosis symptoms, causes and treatments on the NHS website. Alzheimer's Society has a practical guide to supporting someone having hallucinations due to dementia.