Ketamine for depression : The role of dissociative effects

Several trials have reported rapid antidepressant response from the anesthetic drug ketamine although the mechanism behind this effect is not fully understood. Research has focused mainly on ketamine’s action in the brain, including its effects on chemical balance, connections between brain cells and networks, and cognition. Trials with psychedelic drugs have had similar antidepressant results as ketamine, and the quality of the subjective psychedelic experience seems to mediate antidepressant action. Ketamine causes similar alterations of consciousness, which have been viewed as side effects. This thesis examines whether ketamine works in a similar way as psychedelics, where the ketamine-induced dissociative-like experience has a relationship to antidepressant response. Leading theories of depression and ketamine’s action in the brain are presented, and eight studies examining the relationship between ketamine-induced subjective experience and antidepressant response are reviewed. Three included studies found a relationship between psychedelic- and dissociative-like symptoms and reduction in depression, while five did not. The supposed relationship between psychedelic- and dissociative-like symptoms and antidepressant action has not been adequately explored and needs further examination in clinical trials