Delirium, as a concept, stretches back to the age of Hypocrates and has survived repeated attempts at definition and redefinition over the last 2000 years. It is a relatively common disorder, especially in older people with physical illness, has a high morbidity and mortality, is often under-recognized and undertreated, and provides a unique opportunity to delve into acute and florid psychiatric symptomatology, which may aid our understanding of phenomenology.

In this article we will attempt to bring together some current information about delirium, with a particular emphasis on diagnosis, phenomenology, management, and prevention, building on a previous review in this journal 10 years ago.2 While delirium can occur at any age, it is age related and this review will reflect that emphasis, commensurate with the discipline of its authors, while recognizing that the principles of investigation, management, and prevention are age independent. The information base for this article consisted of a Medline search with “delirium” as the MeSH heading (from 1988, yielding 1465 references), the review by Taylor and Lewis, from 1993, and a recent publication