Ketamine shows substantial real-world antidepressant effects in treatment-resistant depression, with about 45% of patients responding and 30% achieving remission, based on a systematic review and meta-analysis of 79 studies involving 2665 patients. The effect varies considerably among individuals; more treatment-resistant cases remit less often, but response rates do not differ. The therapeutic benefit does not significantly decline with repeated treatments, indicating that even the most treatment-resistant patients may benefit and that mid-to-long term treatment is effective for many.
Ketamine is an effective rapid-acting antidepressant, but most research has focused on overall depression severity rather than specific symptom domains. This narrative review synthesizes evidence on ketamine's effects on cognition, anhedonia, suicidality, and psychosocial functionality. The strongest evidence supports ketamine's ability to reduce suicidality, and its rapid action may help prevent suicide. Evidence for other domains is weak, largely because few robust studies have assessed them as primary outcomes. The authors call for future research to examine ketamine's effects on specific depression domains to optimize treatment.