Comparison of average time-to-relapse following ECT versus ketamine – A systematic review

BACKGROUND: Previous systematic reviews and meta-analyses have reported impressive antidepressant effects of ketamine in treatment-resistant depression (TRD). While ketamine has been compared with electroconvulsive therapy (ECT), the gold standard treatment, the extent and durability of its antidepressant effects over longer periods remain unclear. To our knowledge, this is the first systematic review comparing average time-to-relapse between ECT and ketamine in TRD. AIMS: To compare the average time-to-relapse between ECT and ketamine for TRD. METHOD: We conducted this systematic review using PubMed, Medline, ScienceDirect, Cochrane Library, Ovid, PsycNET, Embase and Google Scholar, against predetermined criteria. PROSPERO ID: CRD42025643824. RESULTS: Thirteen studies met inclusion criteria: 10 examined ketamine/(s)ketamine, and 3 focused on ECT. Twelve were randomised controlled trials (RCTs), and one was retrospective. Heterogeneity was observed in dosing regimens and administration schedules, with some studies having limited follow-up and small sample sizes. Findings are synthesised narratively. In summary, there is evidence for sustained therapeutic potential of both ECT and ketamine, ECT possibly being associated with longer remission. Increased dose, frequency and use of maintenance ECT/ketamine appear to prolong remission, and continuing oral antidepressants may prolong this further. It should also be noted that this review excluded studies involving psychotic depression, leading to the exclusion of some head-to-head studies, thus limiting the generalisability of the findings in these populations. CONCLUSION: There is currently a lack of studies within our inclusion criteria that directly compare time-to-relapse after ECT and ketamine, preventing formal statistical analysis. More high-quality, large-scale RCTs directly comparing these treatment modalities with longer follow-up times are needed.