In people with treatment-resistant depression who do not have psychosis, intravenous ketamine works as well as electroconvulsive therapy (ECT) overall. Among outpatients with moderately severe or severe depression, ketamine produced greater improvement in depressive symptoms than ECT. In contrast, inpatients with very severe depression improved more with ECT early in treatment, though by the end of the three-week course both treatments were similarly effective. Higher premorbid intelligence and a diagnosis of posttraumatic stress disorder were linked to greater improvement with ECT, but not with ketamine. These findings may help patients and clinicians decide between the two treatments.
In a multisite randomized trial comparing cognitive effects of intravenous ketamine and electroconvulsive therapy (ECT) in patients with treatment-resistant depression, those receiving six ketamine treatments showed superior cognitive functioning after a three-week treatment course compared with those receiving nine ECT sessions. No significant differences in cognitive task performance were associated with response to either treatment. Among responders followed for up to six months, no group differences emerged. Subjective memory measures were mixed: both groups improved on the Squire Memory Complaint Questionnaire, with ketamine recipients reporting greater functional gains, while ketamine-treated patients reported improvements on a global self-evaluation of memory but ECT-treated patients reported a decline. Within the ketamine group, improvements in executive functioning and cognitive flexibility survived adjustment for changes in depression, suggesting partial independence of cognitive and mood effects.