Delirium

Delirium is an acute, often frightening disturbance in attention, awareness, and cognition that develops over a short period — hours to days — and tends to fluctuate in severity throughout the day. Unlike dementia, which is a chronic, gradually progressive condition, delirium is typically caused by an underlying, often reversible medical problem — infection, medication effects, withdrawal, organ dysfunction — and constitutes a medical emergency requiring urgent evaluation to identify and treat the underlying cause.

Delirium is defined by a disturbance in attention and awareness developing over a short period, representing a change from baseline and tending to fluctuate in severity during the day, together with an additional disturbance in cognition (memory, disorientation, language, or perception). It is not better explained by another neurocognitive disorder and does not occur in the context of severely reduced arousal such as coma, and there must be evidence the disturbance is a direct physiological consequence of a medical condition, substance intoxication or withdrawal, medication, or multiple causes.

Common causes include infection (particularly urinary tract infections and pneumonia, especially in older adults), medication effects or interactions — particularly anticholinergic medications, opioids, benzodiazepines, and polypharmacy — substance intoxication or withdrawal (alcohol withdrawal delirium is a specific, dangerous cause), metabolic disturbances (electrolyte imbalance, dehydration, low blood sugar, organ failure), surgery and anesthesia, severe pain, sleep deprivation, uncorrected sensory impairment, and unfamiliar hospital environments.

• Older age
• Pre-existing dementia or cognitive impairment
• Multiple medications (polypharmacy)
• Severe or multiple medical illnesses, or recent surgery
• Sensory impairment — uncorrected vision or hearing loss
• Severe pain or sleep deprivation
• Alcohol use disorder, given withdrawal risk
• Dehydration or malnutrition
• An unfamiliar or overstimulating environment, such as an ICU

Delirium reflects a global, acute dysfunction of brain networks involved in attention and arousal, thought to result from a combination of neurotransmitter imbalance — particularly reduced acetylcholine activity and excess dopamine — neuroinflammation triggered by the underlying medical illness, and disrupted connectivity between brain regions. Unlike the structural, progressive brain changes of dementia, the changes in delirium are generally considered functional and reversible once the underlying cause is treated, though recovery can take time, and delirium can sometimes accelerate underlying cognitive decline.

• Sudden onset of confusion and disorientation to time, place, or person
• Reduced ability to focus, sustain, or shift attention
• Fluctuating alertness — ranging from drowsy to agitated, sometimes within the same day
• Disorganized thinking or rambling speech
• Memory difficulties
• Perceptual disturbances, including hallucinations in some cases
• Disrupted sleep-wake cycle
• Emotional lability — rapid, unpredictable mood shifts
• Hypoactive subtype: withdrawal, reduced activity, sluggishness (often under-recognized and mistaken for depression or fatigue)
• Hyperactive subtype: agitation, restlessness, combativeness

• Disturbance in attention and awareness developing acutely (hours to days) and fluctuating in severity
• An additional disturbance in cognition
• Not better explained by a pre-existing neurocognitive disorder
• Not occurring in the context of severely reduced arousal or coma
• Evidence the disturbance is caused by an underlying medical condition, substance, medication, or combination of causes

Conditions a psychiatrist will consider and rule out before confirming this diagnosis:

Dementia

Chronic and gradually progressive, without the acute onset or fluctuating course of delirium, though the two frequently co-occur and pre-existing dementia is a major risk factor for delirium.

Depression

Hypoactive delirium can be mistaken for depression given withdrawal and reduced activity, but delirium involves attention and cognitive disturbance with fluctuation that depression does not.

Primary psychotic disorders

Hallucinations can occur in both, but delirium has an identifiable acute medical cause and fluctuating attention, unlike primary psychosis.

Non-convulsive status epilepticus

A seizure-related cause of acute confusion that can mimic delirium, sometimes requiring EEG to distinguish.

• Urgent, thorough medical workup to identify the underlying cause — physical examination and vital signs
• Blood tests: infection markers, electrolytes, glucose, kidney/liver function, thyroid function
• Urinalysis, oxygen saturation, and review of all medications for potential culprits
• Further tests as clinically indicated: brain imaging, chest X-ray, or lumbar puncture
• Validated screening tools such as the Confusion Assessment Method (CAM) to identify and track delirium at the bedside

Identifying and treating the underlying medical cause is the essential first priority — delirium is a symptom of an underlying problem, not a standalone psychiatric illness treated with psychiatric medication alone. Supportive, non-pharmacological measures — reorientation, ensuring glasses/hearing aids are available, minimizing unnecessary noise, maintaining a normal day-night light cycle, family presence — are central to management, and medication is used cautiously and only when necessary for safety.

Low-dose antipsychotics (e.g., haloperidol, risperidone, quetiapine)

May be used cautiously and briefly for severe agitation or distressing hallucinations posing a safety risk, alongside treatment of the underlying cause.

Benzodiazepines

Generally avoided except specifically for alcohol or benzodiazepine withdrawal delirium, since they can worsen delirium from other causes.

Medication review

Anticholinergic medications and other known delirium-inducing drugs should be reviewed and minimized or stopped where possible.

Reorientation strategies

Calm, consistent reminders of time, place, and situation.

Family involvement

Familiar presence and objects support orientation and reduce distress.

Psychoeducation for family

Helps reduce fear and distress when a loved one seems suddenly, dramatically different.

• Maintain hydration and nutrition
• Ensure sensory aids — glasses, hearing aids — are used
• Promote normal sleep-wake cycles: natural light during the day, dark and quiet at night
• Encourage early mobilization after surgery or illness where medically appropriate
• Minimize unnecessary medications
• Bring familiar objects and encourage family presence to support orientation

Delirium is generally reversible once the underlying cause is identified and treated, though recovery can take days to weeks. In older adults or those with pre-existing cognitive impairment, full recovery to baseline is not always achieved, and delirium can be associated with accelerated cognitive decline. Delirium is associated with significantly increased risk of complications, longer hospital stays, and increased mortality if not promptly recognized and treated.

• Proactive, multicomponent prevention protocols in hospital settings — reorientation, sleep protocols, early mobilization, addressing sensory impairment, minimizing unnecessary medications and restraints
• Careful medication review in older adults to avoid high-risk drugs where possible
• Prompt treatment of infections and other acute illnesses

Understand delirium as a medical emergency signaling an underlying problem, not simply 'confusion of old age' or a sign of permanent decline. Provide calm reassurance and gentle reorientation rather than arguing or correcting harshly. Bring familiar objects, ensure glasses and hearing aids are available, and advocate for minimizing unnecessary tubes, restraints, or overnight disruptions in hospital. Seek urgent medical attention immediately for any sudden, significant change in alertness, attention, or confusion in a loved one, especially an older adult.

1. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th Edition, Text Revision (DSM-5-TR).
2. World Health Organization. International Classification of Diseases, 11th Revision (ICD-11).
3. American Delirium Society.
4. National Institute for Health and Care Excellence (NICE). Delirium: prevention, diagnosis and management.