Which residual symptoms predict relapse after successful electroconvulsive therapy for late-life depression?

The risk of relapse following successful acute-phase treatment of late-life depression (LLD), including electroconvulsive therapy (ECT), is substantial. In order to improve reliable prediction of individuals' risk of relapse, we assessed the association between individual residual symptoms following a successful acute course of ECT for LLD and relapse at six-month follow-up. This prospective cohort study was part of the MODECT study, which included 110 patients aged 55 years and older with major depressive disorder. Participants who showed response to the index ECT course were monitored for relapse for six months. We used multivariable stepwise logistic regression models to assess the association between the scores on the 10 individual Montgomery-Åsberg Depression Rating Scale (MADRS) items at the end of the acute ECT course and relapse at six-month follow-up. Of the 80 responders with available six-month follow-up data (58.75% of which had psychotic features at baseline), 36.25% had relapsed. Higher scores on the MADRS items ‘reduced sleep’ (odds ratio (OR) = 2.03, 95% confidence interval (CI) = 1.11–3.69, p = 0.0214) and ‘lassitude’ (OR = 1.62, 95% CI = 1.00–2.62, p = 0.0497) at the end of the acute ECT course were significantly associated with increased risk of relapse at six-month follow-up. In conclusion, some residual depressive symptoms, including sleep disturbance and lassitude, may help better identify patients vulnerable to relapse following a successful acute course of ECT for LLD. If these findings can be replicated, studies assessing interventions that target specific residual symptoms may further reduce post-ECT depressive relapse rates.