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BACKGORUND Maintenance electroconvulsive therapy (mECT) is underused in the treatment of bipolar disorder (BD). We aimed to study the real-life effectiveness of mECT in BD. METHODS Naturalistic 3-year mirror-image study in individuals diagnosed with BD who underwent mECT at a tertiary hospital. Intra-subject comparisons of psychiatric hospitalization were performed using McNemar test. Days and number of psychiatric hospitalizations before and during mECT were compared through wilcoxon signed-rank test. Mean annual days and mean annual number of psychiatric hospitalizations per patient were compared by means of the rate ratio (RR) estimation through a generalized estimating equation (GEE) model. RESULTS A total of 43 patients were included and 37 required psychiatric hospitalization during the study. The use of mECT showed an effectiveness of 62.2% for preventing psychiatric hospitalizations (p<0.01). We found significant reduction in days and number of psychiatric hospitalizations during mECT compared to before mECT (p<0.01). Comparison of the 3-year period before/during mECT showed a reduction in mean annual days (RR=0.14; 95%CI: 0.07-0.29) and mean annual number (RR=0.24; 95%CI: 0.13-0.43) of psychiatric hospitalizations, without substantial changes for adjusted models for gender and age of onset of the illness. LIMITATIONS The main limitations of this study consisted of the mirror-image retrospective naturalistic study design, the relatively small sample size, and possibly patient selection bias. CONCLUSIONS mECT reduced the number of psychiatric hospitalizations and hospitalization days in BD. The use of mECT outlines a mood stabilizing effect in BD. This naturalistic study supports the effectiveness of mECT in BD across several mood states.