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6D70

Delirium

Description

Delirium is characterized by a disturbance of attention, orientation, and awareness that develops within a short period of time, typically presenting as significant confusion or global neurocognitive impairment, with transient symptoms that may fluctuate depending on the underlying causal condition or etiology. Delirium often includes disturbance of behaviour and emotion, and may include impairment in multiple cognitive domains. A disturbance of the sleep-wake cycle, including reduced arousal of acute onset or total sleep loss with reversal of the sleep-wake cycle, may also be present. Delirium may be caused by the direct physiological effects of a medical condition not classified under mental, behavioural or neurodevelopmental disorders, by the direct physiological effects of a substance or medication, including withdrawal, or by multiple or unknown etiological factors. [1]

Diagnostic requirements

WHO clinical descriptions and diagnostic requirements [1,2].

Delirium includes the following categories:

  • 6D70 Delirium
    • 6D70.0 Delirium Due to Disease Classified Elsewhere
    • 6D70.1 Delirium Due to Psychoactive Substances Including Medications
    • 6D70.2 Delirium Due to Multiple Etiological Factors
    • 6D70.Y Delirium, Other Specified Cause
    • 6D70.Z Delirium, Unspecified or Unknown Cause

6D70 General Diagnostic Requirements for Delirium

Essential (Required) Features:

  • A disturbance of attention, orientation, and awareness developing within a short period of time (e.g., within hours or days), typically presenting as significant confusion or global neurocognitive impairment with transient symptoms that may fluctuate depending on the underlying causal condition or etiology.
  • The disturbance represents a change from the individual’s baseline functioning.
  • Delirium may be caused by the direct physiological effects of a medical condition not classified under Mental, Behavioural or Neurodevelopmental Disorders, by the direct physiological effects of a substance or medication, including withdrawal, or by multiple or unknown etiological factors.
  • The symptoms are not better accounted for by a pre-existing or evolving Neurocognitive Disorder (i.e., Amnestic Disorder, Mild Neurocognitive Disorder, or Dementia) or by another mental disorder (e.g., Schizophrenia or Other Primary Psychotic Disorder, a Mood Disorder, Post-Traumatic Stress Disorder, a Dissociative Disorder).
  • The symptoms are not better accounted for by a typical syndrome of Substance Intoxication or Substance Withdrawal for a substance or medication that is known to be present, although Delirium can occur as a complication of intoxication or withdrawal states (see Delirium Due to Psychoactive Substances Including Medications, below).

Additional Clinical Features:

  • In Delirium, cognition is typically impaired in a global manner, such that multiple areas of neurocognitive functioning are impaired upon assessment.
  • Delirium may include impaired perception, which can manifest as illusions (i.e., misinterpretations of sensory inputs), delusions, or hallucinations.
  • Delirium often includes disturbance of emotion, including anxiety symptoms, depressed mood, irritability, fear, anger, euphoria, or apathy.
  • Behavioural symptoms may be present (e.g., agitation, restlessness, impulsivity). A disturbance of the sleep-wake cycle, including reduced arousal of acute onset or total sleep loss followed by reversal of the sleep-wake cycle, may also be present.
  • The presence of a pre-existing Neurocognitive Disorder can increase the risk for Delirium and complicate its course.

Boundary with Normality (Threshold):

  • Normal aging is typically associated with some degree of cognitive change. Delirium is differentiated from age-related cognitive changes by the sudden onset of symptoms (e.g., within hours or days), the presence of significant confusion and/or global neurocognitive impairment, and the transient and typically fluctuating symptom presentation.

Course Features:

  • Onset of symptoms is typically sudden (e.g., within hours or days) with a transient and/or fluctuating course.
  • Symptoms are generally expected to remit with treatment of the underlying etiology or the elimination of the causative substance from the body.

Developmental Presentations:

  • Susceptibility to Delirium in infancy and childhood may be greater than in early and middle adulthood.
  • In childhood, Delirium may be related to febrile illnesses and certain medications (e.g., anticholinergics).
  • Older individuals are especially susceptible to Delirium compared with younger adults.

Culture-Related Features:

  • Performance during clinical assessment may vary according to cultural and/or linguistic factors. When assessing impairment in neurocognitive functioning and activities of daily living, cultural and linguistic factors should be considered and accounted for when possible.
  • When standardized neuropsychological/cognitive testing is utilized for determination of neurocognitive impairment, performance should be measured with appropriately normed, standardized tests. In situations where appropriately normed and standardized tests are not available, assessment of neurocognitive functioning requires greater reliance on clinical judgment. (See General Cultural Considerations for Neurocognitive Disorders for additional information and examples.)

Boundaries with Other Disorders and Conditions (Differential Diagnosis):

  • Boundary with Dementia: Delirium is differentiated from other Neurocognitive Disorders in that the former is characterized by global neurocognitive impairment and confusion that have a precipitous onset, are transient, and fluctuate depending on the underlying causal condition or etiology. Dementia is more typically characterized by impairment in specific neurocognitive abilities and is often progressive and more gradual in onset. Individuals with Dementia are at increased risk for Delirium, and those who develop acute disturbances in attention, orientation, and awareness should be assigned an additional diagnosis of Delirium and evaluated to determine its specific etiology.
  • Boundary with neurocognitive impairment associated with acquired or traumatic brain injuries: Delirium is differentiated from an acute confusional or agitated state related to acquired or traumatic brain injuries by the absence of evidence of a preceding neurological injury or event (e.g., traumatic brain injury, cerebral hemorrhage, stroke).
  • Boundary with Transient Global Amnesia: Unlike Delirium, Transient Global Amnesia is characterized by the presence of isolated memory impairment alongside intact functioning in other cognitive areas (e.g., naming skills, self-identification). Although both disorders may present with memory impairment, Delirium is frequently characterized by additional symptoms including significant confusion, global neurocognitive impairment, and behavioural and emotional disturbance (e.g., hallucinations, agitation).
  • Boundary with Factitious Disorder and Malingering: In Factitious Disorder and Malingering, the neurocognitive symptoms characteristic of Delirium are consciously feigned. Feigned or induced symptoms may be, though are not necessarily, atypical in pattern, magnitude, or course or may be medically implausible. Individuals with Factitious Disorder feign neurocognitive symptoms in order to seek attention, especially from health providers and to assume the sick role. Malingering is characterized by intentional feigning of neurocognitive impairment for obvious external incentives (e.g., disability payments).
  • Boundary with Schizophrenia or Other Primary Psychotic Disorder: Delirium accompanied by hallucinations and/or delusions is differentiated from Schizophrenia or Other Primary Psychotic Disorders by the absence of other characteristics of these disorders and by symptoms that are transient and fluctuate depending on the underlying causal condition or etiology.
  • Boundary with Dissociative Amnesia: Selective memory deficits are present in Dissociative Amnesia and may be accompanied by confusion about identity if dissociative fugue is present. Dissociative Amnesia is not characterized by disturbances in attention or awareness, general confusion, or global neurocognitive impairment, which are features of Delirium.

For presentations characterized by a disturbance of attention, orientation, and awareness developing within a short period of time (e.g., within hours or days) whose cause is identified but is not adequately captured by any of the other available Delirium categories, the following diagnosis may be appropriate:

6D70.Y Delirium, Other Specified Cause

Essential (Required) Features:

  • All diagnostic requirements for Delirium are met.
  • The Delirium is presumed to be attributable to an identified cause that is not adequately captured by any of the other available Delirium categories.
  • This judgment depends on establishing that:
    • The specified cause is known to be capable of producing Delirium; and
    • The course of the Delirium (e.g., onset, trajectory of symptoms, response to treatment) is consistent with the specified cause.

Note: The ICD-11 diagnosis corresponding to the presumed etiology should also be assigned.

For presentations characterized by a disturbance of attention, orientation, and awareness developing within a short period of time (e.g., within hours or days) whose cause is unknown or unspecified, the following diagnosis may be appropriate:

6D70.Z Delirium, Unknown or Unspecified Cause

Essential (Required) Features:

  • All diagnostic requirements for Delirium are met.
  • The cause of the Delirium is unknown or unspecified.

Subcategories

References

  1. World Health Organization. International Classification of Diseases, 11th Revision, for Mortality and Morbidity Statistics (ICD-11 MMS), 2026-01 release. World Health Organization; 2026.
  2. World Health Organization. Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural or Neurodevelopmental Disorders (CDDR). World Health Organization; 2024.

WHO text reproduced without changes from the WHO ICD-11 API. © World Health Organization, licensed under CC BY-ND 3.0 IGO. View this entry in the WHO ICD-11 browser.