Left versus right repetitive transcranial magnetic stimulation in treating major depression: a meta-analysis of randomised controlled trials

Although the majority of randomised controlled trials suggest that major depressive disorder (MDD, major depression) and treatment-resistant depression can be effectively treated by applying either high- (HF) or low-frequency (LF) repetitive transcranial magnetic stimulation (rTMS) to the left and right dorsolateral prefrontal cortex (DLPFC), respectively, it is not clear which rTMS approach is more effective or safer. This systematic review and meta-analysis was conducted on randomised controlled trials on HF and LF rTMS applied to the left and right DLPFC, respectively, for the treatment of MDD. Eight randomised controlled trials composed of 249 patients were selected to compare the effects of LF (≤ 1 Hz) rTMS over the right DLPFC to HF (10-20 Hz) rTMS over the left DLPFC. The therapeutic effects of both approaches were similar (odds ratio (OR) = 1.15; 95% confidence interval = 0.65-2.03). Dropout analysis based on only two studies was insufficient to draw a conclusion on the tolerability of LF rTMS. The pooled examination demonstrated that both rTMS methods were equally effective therapies for MDD. However, considering that LF right-sided rTMS produces fewer side effects and is more protective against seizures, its clinical applicability shows greater promise and should be explored further.