What is delirium?

Delirium is sometimes called an ‘acute confusional state’. It is caused when a physical illness affects the working of the brain. This can cause mental health symptoms including:

  • confusion
  • changes in consciousness
  • attention and thinking
  • behaviour
  • perception.

Although delirium may affect people quite seriously and can take a while to improve, it tends to be a temporary condition.Studies have found that as many as 25% - 33% of people who are admitted to hospital can develop delirium with older people most at risk. Delirium is also common in people who are severely unwell, or who have recently had surgery.Delirium tends to develop quickly, usually over a period of a few hours to a few days. The levels of confusion and disorientation the people experience are often changeable, and is commonly worse at night.

Signs and symptoms of delirium

A person with delirium may:

  • seem unaware of their surroundings and not realise they are in hospital
  • be muddled about the day and the time
  • misunderstand the world around them and perhaps be able to see or hear things that are not real (hallucinations)
  • have a disturbance to their sleep pattern and be excessively drowsy by day, or wakeful and restless by night
  • have problems with speech or understanding what is being said to them
  • show agitation and restlessness, particularly if they are unable to communicate effectively
    • sometimes this can lead to aggression, even though this may be quite out of character with the person’s usual behaviour
    • often this occurs when people are frightened or are not able to understand what is happening to them
  • have feelings of worry, anxiety, fear, irritability or apathy
  • seem fine one day then confused again on another visit.

Causes of delirium

The specialist involved will have explained their thoughts on why this delirium has developed. There are many possible causes of delirium and there may be more than one reason the delirium has developed. Occasionally, a specific cause for an episode of delirium cannot be found.

In people over 65 years, delirium is commonly caused by:

  • Infections
  • breathing or heart problems
  • dehydration
  • taking a combination of medications
  • stopping a medication.

Older people are more likely to develop delirium if they are in hospital and if they already have a memory problem.

What we will do 

We will treat the physical illness or factors which have caused the delirium. Delirium is not a permanent condition although the symptoms may take a while to resolve; even once the causes have been addressed. This may take days, weeks, or even several months if a person has other health problems, pre-existing dementia or is over 65.   

  • identify and treat the cause of the delirium
  • monitor your/the patient’s progress
  • give advice on ways to reduce the effects of the illness and keep the person comfortable and safe.

Occasionally people with delirium become distressed or agitated and this may cause a risk to themselves or others. Medication is sometimes used to help calm people in these situations. It is only short-term and will be closely monitored.

Please talk to us about any concerns you have. 

What can relatives and friends do to help?

To give your relative or friend the best chance of a quick recovery there are ways you can help them to feel orientated and secure when you visit:

  • make sure any spectacles or hearing aids are working and are worn
  • a calm and reassuring approach when visiting would be beneficial; familiar people also reduce the severity of confusion and stress
  • avoid getting into arguments with the person, for example if they struggle to make sense of things - they may not be able to understand your explanation, or may not be able to remember it for very long.
  • It is sometimes better to reassure the person that you have understood their concerns, and try to move the conversation on to a different topic
  • a familiar photograph close by and a clock or watch to help orientation
  • books or magazines that the person would normally read may be handy to use as a distraction
  • encourage the person to drink fluids regularly (check first with staff) - a supply of their favourite soft drink would be useful
  • encourage the person to walk or move around from time to time, bearing in mind advice from physiotherapy and ward staff.

If you think your relative or friend is in pain or might be constipated please speak to a ward nurse.  

Long term effects of delirium

Although most people experience a full recovery from delirium, it may increase the risk of complications from other medical conditions. 


These include:

  • post-operative complications
  • longer recuperation periods
  • longer hospital stays
  • needing more help after discharge from hospital.

Older people may take longer to recover from delirium, and may experience mild lasting effects.Some people who have experienced delirium do not remember what has happened while others have vivid and possibly frightening memories of it.

People who have had delirium are more likely to experience it again in the future. It is important to discuss the causes of delirium with a doctor or nurse, so that you will know the risk factors that may lead to delirium in the future.

It is helpful to be able to recognise the early signs of the condition, so that the causes can be sought as soon as possible.

If you have experienced delirium it is important that you talk to your doctor or nurse about your experiences.

Further information

Please talk to your hospital, family doctor, nurse or your care co-ordinator. 


Reference: L676 
Version: V4
Last updated: 23 / 11 / 2017
Archive date: 23 / 11 / 2020


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