A brief review of the history of delirium as a mental disorder
DIMITRIOS ADAMIS (Oxleas NHS Trust, UK), ADRIAN TRELOAR (Oxleas NHS Trust, UK), FINBARR C. MARTIN (Guy’s and St Thomas’ NHS Foundation Trust, London) and ALASTAIR J. D. MACDONALD (Institute of Psychiatry, London)
History of Psychiatry, 18(4): 459–469 (2007)
We review the most important concepts about delirium, from ancient times until the twentieth century. We also focus on the question of how these concepts have dealt with the particular problems posed by prognosis and outcome. Although different terms have been used, a robust description of delirium has existed since antiquity – at some times as a symptom and at others as a syndrome. It is clear that, throughout the millennia, delirium has been – and still is – a highly lethal syndrome; a poor mental outcome for survivors was often noted. Not until the twentieth century was it thought that delirium was marked by a full recovery among survivors, and this was probably due to the desire for a clear distinction from dementia.
Despite the ‘three millennia of delirium research’, delirium remains hard to define and difficult to study. Delirium is usually assumed to be an acute, fluctuating, transient and reversible condition caused by physical illness. Once the acute episode has remitted, the premorbid level of functioning is reached again, with personality reappearing intact. But experience and research shows that this is not always the case; delirium is often irreversible especially in the elderly and those with pre-existing dementia. While the two international classifications (ICD, DSM) can increase the concurred validity of a diagnosis between the professionals and facilitate the communication between them, both systems have been criticized regarding the definition of delirium. ICD and DSM define delirium as a disorder (even when the aetiology is known) but then characterize delirium as a syndrome. As the two systems do not define delirium according to outcome, it has been argued that (at least in survivors) delirium should be defined according to cognitive reversibility.