Delirium: what it is, symptoms, causes, treatment and how long it lasts

NHS inform describes delirium, also called an acute confusional state, as when someone's mental function has a sudden change. It comes on quickly, often over hours or days. As well as showing confusion, people with delirium can be sleepy, agitated, have altered beliefs or see hallucinations.

The Royal College of Psychiatrists says delirium is a state of mental confusion that starts suddenly and is caused by a physical condition of some sort. It often starts suddenly and usually lifts when the condition causing it gets better. It can be frightening, both for the person and for those around them, and is usually worse at night.

NHS inform says delirium is one of the most common medical emergencies.

NHS inform lists symptoms people with delirium may experience. It says symptoms are sometimes worse in the evenings or overnight. Relatives and carers are often the first to notice signs, because the key change is in the person's normal mental function.

• Being confused, or more confused than normal.

• Being sleepy and less responsive.

• Being very agitated or restless.

• A change in sleeping pattern, such as being awake at night and sleeping during the day.

• Suspiciousness or a loss of trust.

• Seeing or hearing things that are not real.

NHS inform says delirium is caused by a change in the way the brain functions, and many things can trigger this. The Royal College of Psychiatrists says there is often more than one cause, but sometimes the cause is never found.

NHS inform says anyone can get delirium, but some things increase the risk. The Royal College of Psychiatrists adds that delirium is more common after recent surgery, in people with a terminal illness, or with an illness of the brain such as an infection, a stroke or a head injury.

• Being over 65.

• Having dementia.

• Being frail.

• Hearing or sight loss.

• Having had delirium before.

• Alcohol misuse.

NHS inform says most delirium lasts a few days but in some cases it can persist for weeks or even months. Delirium can continue even when all triggers have been addressed, in which case ongoing supportive care and help is needed. In other cases it slowly improves, though not everyone recovers to the same mental function they had before.

The Royal College of Psychiatrists says delirium usually gets better when the cause is treated. You may get better quickly, but sometimes it can take several days or weeks, and may leave vivid memories. After recovery, NHS inform says there is an increased risk of dementia, and people who experienced distress may develop post-traumatic stress symptoms such as intrusive memories, anxiety and depression.

NHS inform says treatment has several aspects. First, treating the triggers: delirium is usually caused by one or more triggers, so care starts by working out what they are and treating them as effectively as possible, for example treating a chest infection. Often more than one trigger is present.

Second, treating symptoms. NHS inform says many people are distressed because they feel disorientated and may have paranoia or hallucinations. These symptoms can improve with repeated reassurance and by explaining carefully what is happening. Occasionally healthcare professionals may use antipsychotic drugs or other treatments.

The Royal College of Psychiatrists says sedative medicines may calm someone down but can also make delirium worse, so they should only be prescribed in particular circumstances, such as when a confused person becomes a danger to themselves or others, and at the lowest possible dose for the shortest possible time. Third, recovery: NHS inform says the aim is to get the person back to their usual self through rehabilitation, engagement, hydration and nutrition.

NHS inform and the Royal College of Psychiatrists give similar advice for relatives and carers.

• Make sure hearing aids, glasses and dentures are within reach and working.

• Have a gentle and friendly approach, smile and provide reassurance.

• Talk in short, simple sentences and keep the person informed; repeat things if necessary.

• Try to make sure someone the person knows well is with them, particularly in the evening.

• Keep a calendar or clock within view, and a light on at night.

• Bring familiar objects from home, such as photographs.

• If it is safe, help the person to eat and drink.

• Look after yourself: try to sleep and eat and create a support network.

The two conditions can overlap, and often co-exist, especially in older people. NHS inform says people with dementia are much more likely to develop delirium, and in hospital at least half of older people with delirium will also have dementia.

The NHS says to go to A&E or call 999 if someone suddenly becomes confused. It says many causes of sudden confusion need to be assessed and treated as soon as possible and sometimes it may be life threatening. Do not drive to A&E; ask someone to drive you or call 999, and bring any medicines the person takes.

While waiting for an ambulance, the NHS says to stay with the person, tell them who you are and where they are, keep reassuring them, use simple words and short sentences, and make a note of any medicines they are taking. Do not ask lots of questions, and do not stop them moving around unless they are in danger.

See a GP if you are worried that you or a relative have gradually become more forgetful or confused, because in older people this may be a sign of dementia.

On the NHS sudden confusion is an emergency, assessed through A&E, an acute medical unit or ambulance service. In hospital, healthcare staff identify delirium by assessing core symptoms, often using the 4AT test, as NHS inform describes. Relatives who know the person well are a key source of information.

Some families arrange a private geriatrician or care support for follow-up. In general terms the same principles apply: find and treat triggers, review medicines, support hydration, nutrition, sleep and orientation, and plan follow-up if confusion persists or memory problems continue.