Esketamine has been shown to produce a major antidepressant response in patients with treatment-resistant depression (TRD). We evaluated the factors associated with achieving remission in these individuals.

The study was carried out across four psychiatry departments in Madrid, Spain. Patients aged over 18 years were included if they received esketamine as an augmentation treatment for TRD. Standard esketamine protocol included an induction phase (4 weeks) and a maintenance phase (5 to 8 weeks). Subsequent treatment continuation was proposed. Clinical data and scores at the Clinical Global Impression scales were measured following each esketamine administration.

Sixty-five patients initiated the treatment, and 45 patients (69.2%) completed the standard protocol. The median number of esketamine administrations was 19. The mean age was 53.09 and 52.3% of the patients were females. Out of the whole sample, 36 (55%) of the patients achieved remission over the follow-up. Remission rates elevated to 67% in those who completed the standard protocol, and to 70% in those having received more than 19 esketamine administrations. Achieving remission over the follow-up was associated with the absence of dissociative symptoms, and with completing the standard esketamine protocol (OR = 0.229, p = 0.045; and OR = 4.538, p = 0.025, respectively). Receiving more than 19 esketamine administrations was associated with remission over the follow-up (OR = 6.513, p = 0.006).

Our results suggest that extending the numbers of esketamine administration may increase the chances to obtain remission. Adverse effects did not impact the treatment course.