Causes and Treatment of Delirium

1. Overview & Epidemiology

• Definition: Delirium is an acute, fluctuating disturbance of attention and awareness with an additional cognitive disturbance, caused by a direct physiological consequence of a medical condition, substance intoxication/withdrawal, medication, toxin, or multiple etiologies. It is a medical emergency, not a primary psychiatric disorder.
• Core concept (Gajdos): Cognitive impairment is the cardinal symptom shared by delirium, dementia, and amnestic disorders — but in delirium the hallmark is the clouding of consciousness (acute, fluctuating), which distinguishes it from dementia (clear consciousness).
• Organic mental disorder logic: there is a causal relationship between the organic disease and the psychopathology; the somatic pathology precedes the psychiatric symptoms, and the course of the physical illness and the mental disorder run parallel. A heteroanamnesis (collateral history) is essential.
• Prevalence: very common in the general hospital — roughly 10–30% of hospitalized medical patients, higher in the elderly, post-operative, and ICU populations; frequently under-recognised, especially the hypoactive form.
• Key risk factors: advanced age (>65), pre-existing dementia/cognitive impairment (the single strongest predisposing factor), polypharmacy (especially anticholinergics, benzodiazepines, opioids), sensory impairment, severe illness, dehydration, malnutrition, and immobility.
• Prognosis: usually reversible if the underlying cause is found and treated; persistent delirium signals a missed or untreated etiology. Delirium is associated with increased mortality, longer admissions, and later cognitive decline.

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