Efficacy of ketamine and esketamine on functional outcomes in treatment-resistant depression: A systematic review

Background In recent years, ketamine and esketamine treatment have demonstrated rapid antidepressant effects in adults with treatment-resistant depression (TRD). Hitherto, relatively few studies have reported the effect of ketamine/esketamine treatment on functional outcomes (e.g., psychosocial functioning, workplace functioning). Herein, we review and synthesize extant literature reporting functional outcomes with ketamine/esketamine treatment in adults with TRD. Methods A systematic review of clinical studies reporting subjective or objective ratings of general functioning as primary or secondary outcomes was performed. Results Four randomized-controlled trials, one open-label clinical study and one case series reported on the efficacy of ketamine/esketamine on subjective measures of general functioning. Overall, mixed results were reported with respect to the effect across disparate functional measures (e.g., Sheehan Disability Scale [SDS]) using ketamine/esketamine. A single study demonstrated a significant decrease (i.e., improvement) in SDS total scores in TRD with esketamine treatment; most studies, however, did not report on functional outcomes and have functional outcomes as a (co)-primary outcome measure. Limitations Clinical studies that were included evaluated work- or social-related disability as a secondary outcome using subjective rating scales. Conclusion Functional outcomes in adults with TRD receiving ketamine/esketamine was insufficiently characterized. Available evidence indicates that improvements in general psychosocial functioning is apparent. The association, if any, between symptomatic improvement and functional improvement in TRD, as well as the temporality to improve functioning, are future research vistas.