Last updated: September 29, 2023

Summarytoggle arrow icon

Delirium is a neurocognitive disorder characterized by impairments in attention and awareness (reduced orientation to the environment), as well as other cognitive disturbances (e.g., in memory, language, or perception). Symptoms develop acutely and tend to fluctuate throughout the day. Delirium occurs most commonly in older patients and is typically secondary to another medical condition or polypharmacy. As delirium is common in critically ill patients, prevention is also part of supportive care in the ICU. Although delirium is a reversible confusional state, it warrants urgent medical attention because it may be the first sign of serious underlying disease. Management of delirium focuses on treating the underlying illness and providing supportive care until the confusion resolves. Antipsychotic medications may be used to manage agitation if other measures fail.

Definitiontoggle arrow icon

  • Delirium: a syndrome of acute confusion characterized by fluctuations in awareness, cognition, and attention, that fulfills the diagnostic criteria (e.g., DSM-5 or “Confusion assessment method” criteria) [1][2]
  • Subsyndromal delirium: proposed term for patients with clinical features of delirium that do not fulfill the criteria for a delirium diagnosis. [2]
  • Acute encephalopathy [2]
    • A pathobiological process in the brain that:
      • Is diffuse (i.e., without an associated structural lesion)
      • Develops rapidly (i.e., within hours to days, but < 4 weeks)
      • Can manifest as delirium, stupor, or coma
    • Can be further specified according to the suspected underlying mechanism, e.g., acute toxic-metabolic encephalopathy

Etiologytoggle arrow icon

Delirium is typically secondary to another medical condition or polypharmacy. The following is a nonexhaustive list of common causes of delirium.

Metabolic diseases


CNS pathology

Drugs (drug-induced cognitive impairment) and toxins (toxic encephalopathy)

Cardiorespiratory conditions


Pediatric, older (> 65 years), and hospitalized patients are particularly susceptible to delirium. [3][4][5]

I WATCH DEATH: Infection, Withdrawal, Acute metabolic disorder, Trauma, CNS pathology, Hypoxia, Deficiencies, Endocrine, Acute vascular, Toxins/drugs, and Heavy metals are the major causes of delirium.

Clinical featurestoggle arrow icon

  • The main symptom is an acute (hours to days) alteration in the level of awareness and attention.
  • Other features may include:
  • The severity of symptoms fluctuates throughout the day and worsens in the evening (termed sundowning).
  • Symptoms are reversible; their duration and severity depend on the underlying illness.
  • Delirium is commonly described based on the type of alteration that is seen:
Psychomotor activity Patient groups
Mixed type delirium Fluctuates or stays at baseline Most common type in the general population
Hypoactive delirium Decreased Most common type in the older population
Hyperactive delirium Increased (agitation) Usually seen in delirium due to substance use or substance withdrawal

Diagnosticstoggle arrow icon

Delirium is diagnosed clinically, based on either the DSM 5 or Confusion Assessment Method (CAM) criteria. Further studies should be conducted to determine the underlying etiology.

Delirium should be considered a medical emergency until proven otherwise; it can be a sign of severe underlying pathology and is associated with increased mortality. [5]

Diagnostic criteria [6][7]

Confusion assessment method (CAM) [8]

CAM can be used in the community and most hospital environments to assess delirium; for patients in the ICU or the recovery room, use the modified version, CAM-ICU. [9]

Confusion assessment method (CAM) [7][8]
Feature Definition Description
Feature 1
  • Acute onset with fluctuating course
Feature 2
  • Inattention
  • The patient has trouble focusing, keeping track of the conversation, or can be easily distracted.
Feature 3
  • Altered consciousness
Feature 4
  • Thinking is disorganized.
  • The patient's speech is unclear, they seem incoherent, or the flow of ideas is illogical.

Diagnosis of delirium requires features 1 and 2 PLUS either feature 3 or 4.

DSM-5 diagnostic criteria for delirium [6]

The patient meets all of the following:

  • Attention and awareness are impaired.
  • Acute onset over hours or days with waxing and waning severity
  • ≥ 1 additional disruption in cognition
  • The condition fulfills the following criteria:
    • Absence of preexisting dementia, coma, or severely reduce responsiveness
    • Evidence of an organic underlying cause

Determination of the underlying etiology

Routine laboratory studies [7][10]

The following studies are recommended in all patients with a new presumptive delirium diagnosis.

Further diagnostic studies

These should be guided by clinical suspicion of the underlying process or conducted if no other cause has been identified with routine tests.

Symptom-based diagnostic workup for delirium
Suspected underlying process Concerning features Diagnostic studies
Nutritional (e.g., vitamin deficiencies)
Toxic (e.g., intoxication or withdrawal)
Psychiatric [14]

Diagnosis of delirium is clinical. Identify the underlying precipitating factors for DELIRIUM: Drugs, Electrolyte abnormalities, Lack of medication (withdrawal), Infection, Reduced sensorial input, Intracranial pathology, Urinary retention or fecal impaction, Myocardial and pulmonary disease. [7]

Differential diagnosestoggle arrow icon

The symptoms of delirium overlap with a number of other neurological disorders, including dementia. Additionally, patients with preexisting neurological diseases such as dementia are more vulnerable to developing delirium.


Delirium is most often confused with dementia. However, there are significant differences in the presentation of diseases.

Delirium vs. dementia [15]
Delirium Dementia
  • Insidious
  • Rapid and fluctuating
  • Hours to days
  • Slowly progressive deterioration
  • Months to years
Level of consciousness
  • Impaired (fluctuating)
  • Usually alert
  • Impaired (fluctuating)
  • Usually intact
  • Impaired in the advanced phase
  • Recent memory loss
  • Recent, then remote memory loss
Thought process
  • Disorganized
  • Impoverished
  • Present (often visual or tactile)
  • Can be present in advanced disease
Psychomotor activity
  • Increased or decreased
  • Usually normal
  • Usually abnormal
  • Usually normal
  • Reversible
  • Usually irreversible

Delirium is characterized by acute onset of fluctuations in attention and level of consciousness. In dementia, the onset is insidious and attention and level of consciousness are typically preserved until the advanced phase. [15]

Other [16]

The differential diagnoses listed here are not exhaustive.

Managementtoggle arrow icon

General principles

For the approach to undifferentiated patients with altered mental status, see “Initial management of AMS.”

  • Treatment of the underlying condition: the mainstay of management
    • Consider discontinuing; or reducing the dose of causative medications, e.g., anticholinergics. [7][10]
    • See “Etiology” for a detailed list of conditions.
  • Supportive care: Clinical manifestations, functional limitations, and associated risks of delirium can persist, requiring admission and supportive care.
  • Behavioral emergencies: See “Treatment of agitation in delirium.”

Do not discharge patients from ambulatory settings unless delirium resolves with initial management and an underlying cause has been identified and treated. [17]

In patients requiring admission, consider a higher level of care based on clinical status and monitoring needs.

Supportive care [7][10][16]

A comprehensive care strategy involving multidisciplinary health providers and family members is preferred to prevent and address complications of delirium. [7]

Treatment of agitation in deliriumtoggle arrow icon

Patients with delirium may become agitated or aggressive as a result of acute confusion, particularly in unfamiliar environments.

Nonpharmacological measures

Agitation should initially be managed with nonpharmacologic strategies.

Avoid physical restraints as much as possible in older patients with delirium, as they can worsen distress and agitation, as well as contribute to preventable injuries. [19]

Pharmacotherapy [7]

Medications should be reserved for refractory agitation.

  • Sedating medications should be limited to patients with agitation severe enough to pose a risk to themselves or others.
  • To minimize the risk of worsening delirium with medication:
    • Check for drug interactions.
    • Start with the lowest possible dose.
    • Titrate until agitation reduces.
    • Discontinue the drug as soon as possible.
  • Consider specialist consultation (e.g., psychiatry, geriatrics) for patients who need continual dosing.
  • The recommended dosages for older adults are lower than for younger patients. [7][20]

Antipsychotics [7][20]

Avoid antipsychotics in patients with underlying alcohol withdrawal or benzodiazepine withdrawal (due to the risk of seizures) and in patients at high risk for QTc prolongation (due to the risk of torsades de pointes). [9]

Benzodiazepines [7][10][20]

Benzodiazepines are deliriogenic. Do not treat delirious patients with benzodiazepines unless the delirium is due to alcohol or benzodiazepine withdrawal.

Preventiontoggle arrow icon

Over one-third of cases of delirium can be prevented with nonpharmacological strategies. [5]

  • The following measures can reduce morbidity: [21]
    • Early identification of at-risk patients (see “Etiology”)
    • Regular screening to detect early signs of delirium
    • Tailored care according to risk, e.g., validated monitoring tools and prevention strategies for older patients [9][10][21]
  • Delirium is very common in the ICU; see “Supportive care in the ICU” for additional considerations. [22]

Older patients are at particularly high risk for delirium during hospitalization and benefit from specialized monitoring and prevention. [21]

Prevention strategies

  • Nonpharmacologic prophylaxis
    • Reduce exposure to modifiable risk factors.
      • Avoid drugs that can worsen delirium (e.g., benzodiazepines, anticholinergics, opioids).
      • Avoid restraints if possible.
      • Ensure that the patient is comfortable and that symptoms are well controlled (see “Supportive care” in “Management” section).
    • Reorient the patient regularly.
      • Keep a clock and/or calendar near the patient to help with orientation.
      • Provide visual and hearing aids for patients with impairments.
      • Keep curtains open and lights on during daytime hours.
    • At night, reduce the amount of noise, procedures, and medication administration.
    • Arrange for regular visits from family and friends.
    • Regularly assess at-risk patients using the CAM tool to detect delirium early.
  • Pharmacological prophylaxis: Some medications (e.g., dexmedetomidine, melatonin) have been used to prevent delirium in the critical care/postoperative settings, but benefits are still uncertain. [16]

Uninterrupted sleep is particularly important in patients with delirium, who may experience a worsening of neuropsychiatric symptoms in the evening and at night known as sundowning.

Cholinesterase inhibitors have not been shown to be effective in the prevention or treatment of delirium. However, patients requiring long-term treatment cholinesterase inhibitors can continue to use them. [23][24]

Acute management checklisttoggle arrow icon

Referencestoggle arrow icon

  1. Fong TG et al.. Delirium in elderly adults: diagnosis, prevention and treatment. Nature Reviews Neurology. 2009; 5 (4): p.210-220.doi: 10.1038/nrneurol.2009.24 . | Open in Read by QxMD
  2. Inouye SK, Westendorp RG, Saczynski JS. Delirium in elderly people. Lancet. 2014; 383 (9920): p.911-922.doi: 10.1016/s0140-6736(13)60688-1 . | Open in Read by QxMD
  3. Barr J, Fraser GL, Puntillo K, et al. Clinical Practice Guidelines for the Management of Pain, Agitation, and Delirium in Adult Patients in the Intensive Care Unit. Crit Care Med. 2013; 41 (1): p.263-306.doi: 10.1097/ccm.0b013e3182783b72 . | Open in Read by QxMD
  4. Clinical Practice Guideline for Postoperative Delirium in Older Adults. Updated: October 10, 2014. Accessed: November 19, 2020.
  5. Cavallazzi R, Saad M, Marik PE. Delirium in the ICU: an overview. Ann Intensive Care. 2012; 2 (1): p.49.doi: 10.1186/2110-5820-2-49 . | Open in Read by QxMD
  6. Thom RP, Levy-Carrick NC, Bui M, Silbersweig D. Delirium. Am J Psychiatry. 2019; 176 (10): p.785-793.doi: 10.1176/appi.ajp.2018.18070893 . | Open in Read by QxMD
  7. American Geriatrics Society. American Geriatrics Society Abstracted Clinical Practice Guideline for Postoperative Delirium in Older Adults. J Am Geriatr Soc. 2014; 63 (1): p.142-150.doi: 10.1111/jgs.13281 . | Open in Read by QxMD
  8. Yu A, Wu S, Zhang Z, et al. Cholinesterase inhibitors for the treatment of delirium in non-ICU settings.. Cochrane Database Syst Rev. 2018; 6: p.CD012494.doi: 10.1002/14651858.CD012494.pub2 . | Open in Read by QxMD
  9. Richmond J, Berlin J, Fishkind A, et al. Verbal De-escalation of the Agitated Patient: Consensus Statement of the American Association for Emergency Psychiatry Project BETA De-escalation Workgroup. West J Emerg Med. 2012; 13 (1): p.17-25.doi: 10.5811/westjem.2011.9.6864 . | Open in Read by QxMD
  10. AGS Choosing Wisely Workgroup. American Geriatrics Society Identifies Another Five Things That Healthcare Providers and Patients Should Question. J Am Geriatr Soc. 2014; 62 (5): p.950-960.doi: 10.1111/jgs.12770 . | Open in Read by QxMD
  11. Marcantonio ER. Delirium in Hospitalized Older Adults. N Engl J Med. 2017; 377 (15): p.1456-1466.doi: 10.1056/nejmcp1605501 . | Open in Read by QxMD
  12. Wilson M, Pepper D, Currier G, Holloman G, Feifel D. The Psychopharmacology of Agitation: Consensus Statement of the American Association for Emergency Psychiatry Project BETA Psychopharmacology Workgroup. West J Emerg Med. 2012; 13 (1): p.26-34.doi: 10.5811/westjem.2011.9.6866 . | Open in Read by QxMD
  13. Fong TG, Davis D, Growdon ME, Albuquerque A, Inouye SK. The interface between delirium and dementia in elderly adults. Lancet Neurol. 2015; 14 (8): p.823-832.doi: 10.1016/s1474-4422(15)00101-5 . | Open in Read by QxMD
  14. Ganti L, Kaufman MS, Blitzstein SM. First Aid for the Psychiatry Clerkship. McGraw Hill Professional ; 2016
  15. Ropper A, Klein J, Samuels M. Adams and Victor's Principles of Neurology 10th Edition. McGraw-Hill Education / Medical ; 2014
  16. $Diagnostic and Statistical Manual of Mental Disorders.
  17. Inouye SK. Clarifying Confusion: The Confusion Assessment Method. Ann Intern Med. 1990; 113 (12): p.941.doi: 10.7326/0003-4819-113-12-941 . | Open in Read by QxMD
  18. Sutter R, Rüegg S, Kaplan PW. Epidemiology, diagnosis, and management of nonconvulsive status epilepticus: Opening Pandora's box.. Neurol Clin Pract. 2012; 2 (4): p.275-286.doi: 10.1212/CPJ.0b013e318278be75 . | Open in Read by QxMD
  19. Algren DA, Christian MR. Buyer Beware: Pitfalls in Toxicology Laboratory Testing.. Mo Med. ; 112 (3): p.206-10.
  20. Vilstrup H, Amodio P, Bajaj J, et al. Hepatic encephalopathy in chronic liver disease: 2014 Practice Guideline by the American Association for the Study Of Liver Diseases and the European Association for the Study of the Liver. Hepatology. 2014; 60 (2): p.715-735.doi: 10.1002/hep.27210 . | Open in Read by QxMD
  21. O’Sullivan R, Inouye SK, Meagher D. Delirium and depression: inter-relationship and clinical overlap in elderly people. Lancet Psychiatry. 2014; 1 (4): p.303-311.doi: 10.1016/s2215-0366(14)70281-0 . | Open in Read by QxMD
  22. Walls R, Hockberger R, Gausche-Hill M. Rosen's Emergency Medicine. Elsevier Health Sciences ; 2018
  23. Wilson JE, Mart MF, Cunningham C, et al. Delirium. Nat Rev Dis Primers. 2020; 6 (1).doi: 10.1038/s41572-020-00223-4 . | Open in Read by QxMD
  24. Slooter AJC, Otte WM, Devlin JW, et al. Updated nomenclature of delirium and acute encephalopathy: statement of ten Societies. Intensive Care Med. 2020; 46 (5): p.1020-1022.doi: 10.1007/s00134-019-05907-4 . | Open in Read by QxMD

Icon of a lock3 free articles remaining

You have 3 free member-only articles left this month. Sign up and get unlimited access.
 Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer