Department of Clinical Medicine

Background: Electroconvulsive therapy (ECT) is usually reserved for treatment of severe major depressive disorder (MDD), but may be equally effective in the treatment of moderate-severity MDD. This possibility, however, has only been studied to a very limited extent. We therefore investigated the efficacy of ECT after stratifying patients into severe MDD and moderate-severity MDD. Methods: We used data from the Prolonging Remission in Depressed Elderly (PRIDE) study, in which 240 patients (≥60 years) with MDD were treated with right unilateral ultrabrief pulse ECT, combined with venlafaxine. We used the six-item core depression subscale (HAM-D₆) of the Hamilton Depression Rating Scale to define depression severity. Participants with baseline total scores ≥12 on the HAM-D₆ were considered to have severe MDD, while those with HAM-D₆ total scores <12 were considered to have moderate-severity MDD. Results: Among the participants with severe MDD and moderate-severity MDD, the mean change in the HAM-D₆ total score from baseline to endpoint was -8.2 (95% confidence interval (95%CI) = -7.5; -9.0, paired t-test: p < 0.001) and -5.9 (95%CI = -5.1; -6.6, paired t-test: p < 0.001), respectively. A total of 63% of those with severe MDD and 75% of those with moderate-severity MDD achieved remission (HAM-D₆ total score ≤4) (Pearson's 2-sample chi-squared test of difference between groups: p = 0.27). Limitations: The PRIDE study was not designed to address this research question. Conclusions: ECT combined with venlafaxine appears to be an effective treatment for moderate-severity MDD. It may be appropriate to expand the indications for ECT to include patients with moderate-severity MDD.