Delirium

Delirium (DSM-5-TR 780.09) is an acute, fluctuating disturbance in attention and awareness with cognitive change, typically caused by an underlying medical condition, substance use, or medication effect. It is a medical emergency requiring identification and treatment of the underlying cause.

Overview

Delirium (DSM-5-TR 780.09) is an acute neurocognitive disorder characterized by a disturbance in attention and awareness, accompanied by an additional disturbance in cognition (memory deficit, disorientation, language, visuospatial ability, perception). It develops over a short period of time (hours to days), tends to fluctuate during the course of a day, and represents a change from baseline. The disturbance is not better explained by a pre-existing or evolving neurocognitive disorder and is caused by the direct physiological consequences of another medical condition, substance intoxication or withdrawal, exposure to a toxin, or multiple etiologies.

Delirium is among the most common acute neurocognitive disorders, particularly in hospitalized older adults. Prevalence in hospitalized older adults is approximately 15-20% on general medical units and 50%+ in intensive care, post-surgical, and palliative care contexts. Delirium is associated with substantially elevated mortality, prolonged hospitalization, accelerated cognitive decline, and increased risk of subsequent dementia.

Delirium is fundamentally a medical condition, not a primary mental-health disorder. The DSM-5-TR places it in the Neurocognitive Disorders chapter. The mental-health relevance includes: distinction from primary psychiatric conditions (delirium can mimic depression, mania, psychosis); recognition of delirium in mental-health settings; co-management of delirium and pre-existing mental-health conditions; psychological consequences of delirium experience (post-delirium PTSD-like symptoms are recognized); family education and support during acute episodes.

Common causes include: infection (urinary tract, pneumonia, sepsis), medication effects (anticholinergics, benzodiazepines, opioids, sedatives, polypharmacy), substance withdrawal (alcohol, benzodiazepines), substance intoxication, electrolyte imbalances, dehydration, hypoxia, hypoglycemia, postoperative state, head injury, stroke, hepatic or renal failure, pain. Multifactorial etiology is common, particularly in older adults.

Delirium is treatable when the underlying cause is identified and addressed. Prevention through identification of high-risk patients, environmental modifications, and avoidance of precipitants is increasingly recognized as important particularly in hospital and post-surgical contexts.

This page is provided for clinical education. Acute delirium is a medical emergency requiring evaluation by a physician — most appropriately in emergency or acute-care setting. Mental-health professionals work with delirium primarily through identification, differential diagnosis, family support, and post-delirium psychological care.

Signs and symptoms

Disturbance in attention and awareness — Reduced ability to direct, focus, sustain, or shift attention; reduced orientation to environment.
Acute onset and fluctuating course — Develops over hours to days; severity fluctuates during the day, often worse at night ("sundowning").
Additional cognitive disturbance — Memory deficit, disorientation, language disturbance, visuospatial difficulties, perceptual disturbance — at least one in addition to attention disturbance.
Hyperactive subtype — Agitation, restlessness, hypervigilance, sometimes aggression. More easily recognized; better prognosis.
Hypoactive subtype — Lethargy, decreased motor activity, reduced responsiveness. Often missed (mistaken for depression or sedation); worse prognosis.
Mixed subtype — Fluctuating between hyperactive and hypoactive presentations.
Perceptual disturbances — Visual or auditory hallucinations (often vivid, frightening); illusions; delusions (often persecutory, transient).
Sleep-wake cycle disturbance — Disturbance in sleep-wake cycle; daytime sleepiness, nighttime agitation.
Emotional disturbance — Fear, anxiety, irritability, depression, anger, euphoria — labile emotional state.
Course evidence of underlying cause — Evidence from history, physical examination, or laboratory findings that disturbance is caused by underlying medical condition, substance, medication, or toxin.

Diagnostic context

The DSM-5-TR criteria for Delirium (780.09):

A. A disturbance in attention (i.e., reduced ability to direct, focus, sustain, and shift attention) and awareness (reduced orientation to the environment).
B. The disturbance develops over a short period of time (usually hours to a few days), represents a change from baseline attention and awareness, and tends to fluctuate in severity during the course of a day.
C. An additional disturbance in cognition (e.g., memory deficit, disorientation, language, visuospatial ability, or perception).
D. The disturbances in Criteria A and C are not better explained by another preexisting, established, or evolving neurocognitive disorder and do not occur in the context of a severely reduced level of arousal, such as coma.
E. There is evidence from the history, physical examination, or laboratory findings that the disturbance is a direct physiological consequence of another medical condition, substance intoxication or withdrawal, exposure to a toxin, or due to multiple etiologies.

Specifiers: etiological subtype (substance intoxication delirium, substance withdrawal delirium, medication-induced delirium, delirium due to another medical condition, delirium due to multiple etiologies); activity subtype (hyperactive, hypoactive, mixed); duration (acute — hours to days; persistent — weeks to months).

Differential diagnosis includes:

Major and Mild Neurocognitive Disorders (dementia) — gradual onset; non-fluctuating; chronic course. Delirium can be superimposed on dementia (frequent in older adults).
Major Depressive Disorder, particularly in older adults — depressive episode without acute attention/awareness disturbance.
Schizophrenia and other psychotic disorders.
Acute Stress Disorder, PTSD.
Mania, particularly with severe agitation.
Catatonia.

Validated screening instruments include the Confusion Assessment Method (CAM), CAM-ICU (intensive care), and Delirium Rating Scale.

Causes and risk factors

Delirium has many possible etiologies; multifactorial causes are common particularly in older adults:

Predisposing factors (vulnerability): older age, pre-existing cognitive impairment or dementia, sensory impairment (vision, hearing), multiple medical comorbidities, polypharmacy, malnutrition, dehydration, depression, alcohol use disorder.

Precipitating factors (acute triggers):

Infections: urinary tract infection, pneumonia, sepsis, cellulitis, COVID-19.
Medications: anticholinergics (particularly), benzodiazepines, opioids, sedatives, antipsychotics, polypharmacy, recent medication changes.
Substance withdrawal: alcohol withdrawal (delirium tremens is a medical emergency), benzodiazepine withdrawal, others.
Substance intoxication: alcohol, sedatives, hallucinogens, others.
Metabolic disturbances: electrolyte imbalances, hypoglycemia, hyperglycemia, hyponatremia, uremia, hepatic dysfunction.
Hypoxia and circulatory: respiratory failure, cardiac failure, anemia, shock.
Postoperative: surgery (particularly cardiac, orthopedic), anesthesia effects, pain, sleep disruption.
Neurological: stroke, head injury, seizure, infection of CNS, brain tumor.
Pain: uncontrolled pain elevates delirium risk.
Sleep deprivation: particularly in hospital settings.
Environmental: ICU, unfamiliar environment, sensory deprivation or overload.

End-of-life delirium: common in palliative care; multifactorial; may not always be reversible.

Comorbidity: delirium superimposed on dementia is common and substantially increases mortality. Underlying mental-health conditions (depression, substance use) also affect presentation and management.

Typical treatments

Delirium management is a medical emergency requiring identification and treatment of underlying cause:

Identify and treat underlying cause: infection (antibiotics), medication adjustment (discontinuing precipitating medications when possible), correction of metabolic disturbances, treatment of pain, treatment of withdrawal, treatment of medical comorbidities. The single most important intervention.

Non-pharmacological interventions (first-line):

Reorientation — clocks, calendars, familiar objects, frequent reorientation by staff and family.
Sensory aids — ensuring glasses, hearing aids are available.
Sleep regulation — minimize nighttime disruption, promote daytime activity.
Mobilization — early mobilization when medically safe.
Hydration and nutrition.
Family presence and consistent caregivers.
Minimize physical restraints when possible.
Avoid sleep-disrupting interventions when possible.
Pain management.

Pharmacological interventions (when needed):

Antipsychotics (haloperidol, quetiapine, olanzapine, risperidone) for severe agitation, hallucinations, or risk of harm — short-term, lowest effective dose, careful monitoring. Antipsychotics do not treat delirium itself, only manage symptoms; evidence on benefit is limited.
Benzodiazepines avoided except for alcohol or benzodiazepine withdrawal delirium (where they are first-line).
Avoid anticholinergic medications.
Polypharmacy review and reduction when possible.

Prevention:

HELP (Hospital Elder Life Program) and similar multicomponent prevention programs reduce delirium incidence in hospitalized older adults.
Pre-operative cognitive assessment for high-risk surgical patients.
Medication review for high-risk medications.
Protocols for high-risk units (ICU, post-surgical, geriatric).

Family education and support: delirium is frightening for families; education about transient nature, expected course, role family can play; support during distressing presentations.

Post-delirium care: some patients experience PTSD-like symptoms after delirium episodes (intrusive memories of hallucinations, fear of recurrence); psychological support is appropriate; cognitive rehabilitation may be needed.

Long-term implications: delirium is associated with elevated risk of subsequent dementia, accelerated cognitive decline, and mortality; follow-up cognitive assessment is appropriate.

When to seek help

Delirium is a medical emergency. If you or a family member is showing acute changes in mental state — sudden confusion, difficulty paying attention, disorientation, hallucinations, severe agitation or unusual lethargy — seek immediate medical evaluation:

911 or local emergency department for acute changes.
Family physician for less acute concerning changes; same-day evaluation.
811 — Health Link for telephone advice on whether emergency evaluation is needed.

Particularly urgent evaluation is needed when:

Acute change occurs in older adult.
Recent illness (especially fever, urinary symptoms, respiratory illness).
Recent surgery, hospitalization, or medication change.
Suspected substance intoxication or withdrawal (particularly alcohol or benzodiazepine).
Acute medical conditions (suspected stroke, head injury, severe infection, cardiac event).
Severe agitation with risk of harm.
Severe lethargy with reduced responsiveness.

Mental-health professional involvement is appropriate when delirium is recognized in mental-health settings, when differential diagnosis with primary psychiatric conditions is needed, when family support during acute episodes is needed, when post-delirium psychological care is needed, or when chronic mental-health conditions need co-management with delirium.

For mental-health crisis: 9-8-8 (Suicide Crisis Helpline). For caregiver support: 211.

Frequently asked questions

How is delirium different from dementia?

Delirium is acute (hours to days), fluctuating, with prominent attention disturbance, and caused by an identifiable medical or substance precipitant. Dementia is gradual (months to years), progressive, and reflects underlying neurodegenerative or vascular process. The two can co-occur — delirium superimposed on dementia is common in older hospitalized patients.

Is delirium reversible?

Most delirium is reversible when the underlying cause is identified and treated. Some delirium persists for weeks to months after the precipitant resolves; some may not fully resolve, particularly in older adults with prior cognitive impairment. Delirium is associated with elevated risk of subsequent cognitive decline.

My older parent became confused in the hospital — is this delirium?

Possibly. Hospital-acquired delirium affects 15-50%+ of hospitalized older adults. Causes include infection, medications, sleep disruption, environmental factors, and underlying medical issues. Notify the medical team immediately; specific evaluation and intervention reduce duration and consequences.

Should antipsychotic medication be used?

Antipsychotics manage symptoms but do not treat delirium itself. Evidence on benefit is limited. Used for severe agitation, hallucinations, or risk of harm; lowest effective dose; short duration; careful monitoring. Non-pharmacological approaches are first-line.

How can delirium be prevented?

Multicomponent prevention programs (Hospital Elder Life Program, HELP) substantially reduce delirium incidence: reorientation, sensory aids, sleep regulation, mobilization, hydration, family presence, medication review, pain management. Pre-operative cognitive assessment for high-risk surgical patients. Medication review for high-risk medications particularly in older adults.

My family member experienced PTSD-like symptoms after recovering from delirium — is this real?

Yes. Post-delirium psychological symptoms — intrusive memories of hallucinations, fear of recurrence, anxiety — are increasingly recognized clinically. Specific psychological support is appropriate, including processing of the delirium experience and addressing post-delirium PTSD-like symptoms.

References

American Psychiatric Association. (2022). Diagnostic and Statistical Manual of Mental Disorders (5th ed., text rev.). APA.
Inouye, S. K., Westendorp, R. G. J., & Saczynski, J. S. (2014). Delirium in elderly people. The Lancet, 383(9920), 911–922.
Marcantonio, E. R. (2017). Delirium in hospitalized older adults. New England Journal of Medicine, 377(15), 1456–1466.
Inouye, S. K., et al. (1990). Clarifying confusion: The confusion assessment method. Annals of Internal Medicine, 113(12), 941–948.
Hshieh, T. T., et al. (2015). Effectiveness of multicomponent nonpharmacological delirium interventions: A meta-analysis. JAMA Internal Medicine, 175(4), 512–520.

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ShiftGrit Psychology & Counselling is professionally regulated, certified, and recognized by leading psychology and mental-health organizations across Alberta and Canada. These associations reflect our commitment to ethical practice, clinical standards, and evidence-informed therapy through Identity-Level Therapy and Reconditioning.

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The ShiftGrit Clinical Editorial Team combines the insight of registered psychologists, provisional psychologists, and trained writers to create accessible, evidence-informed therapy resources. All content is clinically reviewed by a Registered Psychologist.