What are the effects of ketamine infusions?

During the infusion itself many people experience a kind of transcendent stat.  The antidepressant effects are almost immediate.  There is some evidence that patients must achieve what is called a dissociative state in which they have a kind of out of body experience in order to get the full antidepressant effects.  There is controversy concerning this point; some studies show that the dissociative state is important for the antidepressant effects and some do not.  In contrast to electroschock there is good evidence that ketamine infusion actually improves cognitive performance.  Because depression can interfere with cognitive performance it is not clear whether it is the ketamine infusion itself which has improved cognitive performance or the improvement in depression.