Ketamine and chronic treatment-resistant depression: real-world practice and after relapse.

Background: Chronic treatment-resistant depression (TRD) poses a major challenge for clinicians. Ketamine has shown a rapid but short-lived antidepressant effect in several studies involving TRD patients with different demographic and clinical profiles. Our study aimed to assess the antidepressant effect of serial infusion sessions of ketamine in patients with chronic TRD and evaluate the severity of symptoms after relapse and the general psychiatric health of the responding patients.