What is Delirium?

Delirium is a state of mental confusion that can occur as a result of illness, surgery or with the use of some medications. Also called “acute confusional state,” delirium usually starts suddenly and can be frightening for the person experiencing it, as well as for those around them.

Symptoms of delirium

Some symptoms are common to delirium, irrespective of cause, while some are cause-specific.

Some examples of symptoms include:

  • Diminished awareness of surroundings
  • Uncertainly about location
  • Inability to understand conversation and speak clearly
  • Vivid, often frightening dreams that continue once awake
  • Auditory hallucination
  • Agitation and restlessness
  • Fear that others are trying to cause harm
  • Feeling drowsy and slow
  • Sleeping during the day but being awake at night
  • Rapid mood swings that vary from scared and anxious to depressed or irritable
  • Confusion that worsens in the evenings

Causes and risks associated with delirium

Delirium is fairly common among hospitalized patients, with around 1 in 10 having a period of delirium. Delirium is more common among older people, those with memory problems, in cases of dementia, after surgery, after brain injury and in those with poor hearing or vision.
Some of the most common causes of delirium include:

  • Infection of the bladder, chest or brain
  • Fever
  • Medication side effect
  • Dehydration
  • Liver or kidney problems
  • Cessation of drug or alcohol use
  • Major surgery
  • Epilepsy
  • Terminal illness


If a person develops confusion out of the blue, urgent medical attention should be sought. Often, the patient is too confused to tell the doctors about their condition and history is often taken from a family member or someone who knows the patient well.

Treatment is aimed at correcting the underlying cause. For example, infection would be treated with antibiotics.

Sedatives can worsen delirium and should only be given in cases where:

  • The patients is extremely anxious
  • The patient has suddenly withdrawn from alcohol or drugs
  • When the patient is at risk of endangering themselves or others
  • In order to calm someone down enough for them to receive treatment

Further Reading

Last Updated: Feb 26, 2019

Dr. Ananya Mandal

Written by

Dr. Ananya Mandal

Dr. Ananya Mandal is a doctor by profession, lecturer by vocation and a medical writer by passion. She specialized in Clinical Pharmacology after her bachelor's (MBBS). For her, health communication is not just writing complicated reviews for professionals but making medical knowledge understandable and available to the general public as well.


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  1. Clifton Edwards Jr Clifton Edwards Jr United States says:

    This article about Delirium was insightful

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News Medical.
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