Meta-Analysis of Left Prefrontal Repetitive Transcranial Magnetic Stimulation (rTMS) to Treat Depression

INTRODUCTION: Depression is a common and severe disorder for which new treatments are needed. Repetitive transcranial magnetic stimulation (rTMS) is a promising new treatment. The purpose of this meta-analysis was to determine whether the literature supports the use of left prefrontal rTMS as a treatment option for depression. METHODS: The literature was searched for randomized sham-controlled trials of left prefrontal rTMS to treat depression using PsycINFO, MEDLINE, and CURRENT CONTENTS as well as two previous meta-analyses of rTMS. Using MetaWin, a Hedges' d effect size and nonparametric variances were calculated in order to determine a cumulative effect size. Tests for heterogeneity and publication bias were also calculated. RESULTS: Twelve of fourteen studies (n = 230) were suitable for analysis. The summary analysis revealed a cumulative effect size of 0.53 (95% CI 0.24-0.82). The test for heterogeneity was not significant (Qtotal = 10.65, df = 11, Prob {chi} = 0.47). The fail-safe result using the Rosenthal's method (55.1 non-significant studies) and the Orwin's method (20.0 non-significant studies) revealed that 20 to 55 studies would have to be unavailable in order to change the cumulative effect to a non-significant result. DISCUSSION: The meta-analysis supports the hypothesis that left prefrontal rTMS is an acute antidepressant treatment with statistically significant effect sizes and measurable clinical improvement.