The incidence of unpleasant dreams after sub-anaesthetic ketamine.

Rationale: Ketamine is an N-methyl-D: -aspartate (NMDA) receptor antagonist with psychotogenic effects and for which there are diverse reports of whether pleasant or unpleasant dreams result during anaesthesia, post-operatively or after sub-anaesthetic use.

Objective: To assess in healthy volunteers the incidence of unpleasant dreams over the three nights after receiving a sub-anaesthetic dose of ketamine, in comparison to placebo, and with retrospective home nightmare frequency as a covariate.

Method: Thirty healthy volunteers completed questionnaires about retrospective home dream recall and were then given either ketamine (n = 19, males = 9, mean age = 23.