Age predicts low-frequency transcranial magnetic stimulation efficacy in major depression

Abstract

Background: Transcranial magnetic stimulation (TMS) effectiveness in major depression has so far been studied mainly with high-frequency (>1 Hz) administration (HF-TMS). However, some available studies with low-frequency TMS (LF-TMS) have provided similar response rates to HF-TMS with better tolerance, but the evidence is mixed and controversial.

Methods: Randomized, controlled, two arm, clinical trial. 34 Major Depression patients were randomly assigned to receive 20 sessions of real or sham TMS of the right dorsolateral prefrontal cortex as adjuvant treatment to pharmacotherapy. The main stimulation parameters were 20 trains at 110% of the motor threshold for 60 s at a frequency of 1 Hz. Blinded external evaluators administered the Hamilton Depression Rating Scale.

Results: Both treatment groups significantly improved, although there were no statistical differences between them. In the real TMS group patients age inversely correlated with improvement of depressive symptoms at the end of the study (r=-0683 p=0.002). The percentage of decrease in scores on the Hamilton Scale was greater in subjects younger than 45 years old vs. others (41.3 +/- 22.6 vs. 15.1 +/- 15.8; t=2.8 df=16, p=0.011). These real TMS subgroups did not differ significantly in their history of previous depressive disorders, or in the refractoriness indicators of the current episode.

Limitations: Small size and highly refractory sample.

Conclusion: Only younger patients benefited from LF-rTMS as adjuvant treatment to antidepressants in this study.