Altered states of consciousness: phenomenology and pharmacology

In recent years a conjunction of factors have brought questions surrounding the phenomenology and pharmacology of altered states of consciousness back onto the scientific agenda. These factors primarily involve the re-classification of psychiatric disorders that took place in 1980 with the publication of DSM III, which contained a number of syndromes that could be characterized in terms of altered states of consciousness, and also the recognition of the phenomenon of awareness under anaesthesia. These issues are outlined against a historical background, in which there had been at the end of the last century a primary psychopathological focus on the question of consciousness that was, however, increasingly neglected during the course of this century until its recent return to prominence.