Sex differences in long-term clinical outcomes following modified electroconvulsive therapy for major depressive disorder

Modified electroconvulsive therapy (MECT) is one of the most effective treatments for patients with major depressive disorder (MDD). This study aimed to examine sex differences in long-term clinical outcomes following MECT in patients with MDD. Clinical data were obtained from mental health centers and psychiatric hospitals across seven provinces participating in the MECT study. Suicide risk and depressive symptoms were assessed using the suicidal module of the Mini International Neuropsychiatric Interview (MINI-C) and the 17-item Hamilton Rating Scale for Depression (HAMD-17), respectively. The efficacy of MECT was evaluated using the Clinical Global Impressions (CGI) scale and the Visual Analogue Scale (VAS). Participants were assessed at five time points: before the first MECT session, postassessment, at 2-week, 1-month, and 6-month follow-ups. Generalized estimating equations were employed to model the longitudinal trajectories of MINI-C and HAMD-17 scores across repeated assessments. The study included 133 patients with MDD (48 males, 36.1%; 85 females, 63.9%). Longitudinal analysis revealed a significant sex-by-time interaction for HAMD-17 scores ( p < 0.05), indicating that the trajectory of depressive symptom improvement differed between males and females. Although no significant sex difference was found in the trajectory of suicide risk (MINI-C) ( χ² = 5.525, p = 0.238), post-hoc comparisons showed that females derived a greater long-term benefit from MECT, with significantly lower HAMD-17 scores at the 6-month follow-up (adjusted mean difference = 2.47, p = 0.042). Regarding treatment response, females reported significantly higher VAS scores than males at the 6-month follow-up (88 vs. 85, Z = -2.906, p = 0.002). These findings suggest that sex may be associated with differential long-term clinical outcomes following MECT, although causal attribution is limited by the observational study design.