Duhaime's Law Dictionary

Delirium Definition:

A sudden onset of acute confusion and hyperactivity.

The 1999 edition of the Merck Manual defines delirium as follows:

"A clinical state characterized by fluctuating disturbances in cognition, mood, attention, arousal and self-awareness which arises acutely...."

Distinguished although similar to dementia. Generally, delirium develops rapidly while dementia usually develops gradually. Delirium may be reversed; dementia, once established, rarely is. Further, delirium can require emergency medical attention whereas those that suffer from dementia do not generally require emergency treatment.


  • Beers, Mark and Berkow, Robert, editors, The Merck Manual of Diagnosis and Therapy, 17th Ed. (Whitehouse Station, New Jersey: Merck Research Laboratories, 1999), page 1393.
  • Duhaime, Lloyd, Duhaime's Legal Dictionary
  • Duhaime, Lloyd, Duhaime's Legal Citations & Abbreviations
  • Pugh, Maureen, (ed.), Stedman's Medical Dictionary, 27th Ed. (Baltimore: Lippincott Williams & Wilkins, 2000), page 470
  • Schmidt, J.E., Attorney's Dictionary of Medicine, Volume 2 (Newark, New Jersey: LexisNexis, 2009), page D-50

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