What causes delirium?

Updated: Apr 25, 2019
  • Author: Kannayiram Alagiakrishnan, MD, MBBS, MPH, MHA; Chief Editor: Glen L Xiong, MD  more...
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Based on the level of psychomotor activity, delirium can be described as hyperactive, hypoactive, or mixed. Hyperactive delirium is observed in patients in a state of alcohol withdrawal or intoxication with phencyclidine (PCP), amphetamine, and lysergic acid diethylamide (LSD). These patients often exhibit agitation, restlessness, hallucinations, or delusions. Hypoactive delirium is observed in patients in states of hepatic encephalopathy and hypercapnia and may be more common in older adults. Hypoactive delirium presents with lethargy, drowsiness, apathy, decreased responsiveness, or slowed motor skills. In mixed delirium, individuals display either relatively normal levels of psychomotor activity or rapidly fluctuating levels of activity. [1, 2]

The mechanism of delirium still is not fully understood. Delirium results from a wide variety of structural or physiological insults. The neuropathogenesis of delirium has been studied in patients with hepatic encephalopathy and alcohol withdrawal. Research in these areas still is limited. The main hypothesis is reversible impairment of cerebral oxidative metabolism and multiple neurotransmitter abnormalities. The following observations support the hypothesis of multiple neurotransmitter abnormalities. [3]

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