Background: Several studies have shown that repetitive transcranial magnetic stimulation (rTMS) treatment is associated with a significant antidepressant effect that can last for several months. Methods: To investigate the mean remission time and the predictors associated with its duration; we performed a large retrospective, naturalistic study with 204 patients who underwent treatment with rTMS. During the periods from 2000 to 2006, we identified and collected the data on 204 patients who underwent rTMS treatment for major depression and who remitted their depression (defined as Hamilton Depression Rating Scores less or equal to 7). Patients were followed up to 6 months after this therapy. Results: Event-free remission with the end point defined as relapse (Hamilton Depression Rating Scores higher than 8) was 75.3% (73.7) at 2 months, 60.0% (74.5) at 3 months, 42.7% (74.8) at 4 months, and 22.6% (74.5) at 6 months. According to a multivariate analysis, only the age and number of sessions were independent predictors of outcome. Although depression severity and use of tricyclics also showed a significant relationship with remission duration, the model including these variables was not adequate to explain our data. Conclusions: The results of this study suggest that young age and additional rTMS sessions are associated with a ong duration of rTMS effects and therefore future trials investigating the effects of maintenance rTMS treatment need to explore further the implication of these factors for depression remission.

Depression and Anxiety 0:1-7, 2009. © 2009 Wiley-Liss, Inc.