Faster and greater antidepressant response to intravenous ketamine in bipolar compared with unipolar treatment-resistant depression: Diagnostic and sex-related findings from a naturalistic study.
Psychiatry research August 1, 2026 Pietro Carmellini, Andrea Fagiolini, Mario Pinzi et al.
In a real-world clinic, intravenous ketamine reduced depressive symptoms in patients with treatment-resistant unipolar and bipolar depression. Both groups improved significantly, but those with bipolar depression showed faster and greater improvement starting at two weeks and lasting through three months. Dissociative side effects were mild and did not increase over time; women with unipolar depression reported higher dissociative symptoms at three months. No sex differences in antidepressant efficacy were found. The findings suggest ketamine is effective for treatment-resistant depression, with stronger benefits for bipolar depression.