Antidepressant efficacy of high and low frequency rTMS at 110% of motor threshold versus sham stimulation over left prefrontal cortex

Background: While the efficacy of repetitive transcranial magnetic stimulation (rTMS) at 10 Hz over the left prefrontal cortex has been repeatedly demonstrated, it is not clear that the optimal parameters for the treatment of depression have been adequately elucidated.

Objectives: We sought to assess the antidepressant effectiveness of high and low frequency at a higher intensity rTMS compared to sham in patients with moderately treatment resistant depression.

Method: The authors conducted a three-week, double-blind, randomized, sham-controlled study of 24 acutely depressed patients given either active 20 Hz (n = 8) or 1 Hz (n = 8) rTMS (at 110% of motor threshold [MT]) or sham treatments (n = 8) over the left prefrontal cortex. Hamilton Depression ratings were analyzed by ANOVA.

Results: Patients on both frequencies showed greater improvement than on sham, which was associated with minor increases in depression. During open continuation to allow 7 weeks of active treatment in all individuals, additional improvement was observed.

Conclusions: The results seen here using 110% of MT for 3 weeks were more robust than those of previous studies of 1-Hz or 20-Hz rTMS for 2 weeks (at 80% and 100% of MT). The results also raise the possibility that both high and low frequency rTMS over left prefrontal cortex (and not just low frequency over the right prefrontal cortex) exert antidepressant effects, but further work is required to assess what parameters may be most effective in general and for a given individual.