Predictors of antidepressant response in clinical trials of transcranial magnetic stimulation

Although previous clinical trials have suggested that repetitive transcranial magnetic stimulation (rTMS) has a significant antidepressant effect, the results of these trials are heterogeneous. We hypothesized that individual patients' characteristics might contribute to such heterogeneity. Our aim was to identify predictors of antidepressant response to rTMS. We pooled data from six separate clinical trials conducted independently, which evaluated the effects of rapid rTMS of the left dorsolateral prefrontal cortex in patients with major depression. We investigated 195 patients with regard to demographic, depression and treatment characteristics, psychiatric and drug history. Results showed that age and treatment refractoriness were significant negative predictors of depression improvement when adjusting these variables to other significant predictors and confounders. These findings were not confounded by methodological differences from the six studies, as the results were adjusted for the study site. In conclusion TMS antidepressant therapy in younger and less treatment-resistant patients is associated with better outcome.