Low-frequency right prefrontal repetitive transcranial magnetic stimulation (rTMS) appears to have antidepressant properties although the effectiveness of this treatment in clinical practice has not been assessed and the optimal stimulation parameters defined. The boundaries of ‘low-frequency’ stimulation are not clear.
A total of 122 patients with treatment-resistant depression were randomized to either 1- or 2-Hz stimulation over right prefrontal cortex (PFC) (one single 15-min train) for 2 weeks. A second 2-week period of treatment was provided for patients showing initial response (>20% reduction in HAMD score).
One hundred eighteen patients received a full 2 weeks of treatment (63 − 1 Hz, 55 − 2 Hz). There was a mean reduction in HAMD scores of 30.1 ± 29.8% in the 1-Hz group and 33.2 ± 31.7% in the 2-Hz group (P > 0.05). Seventy-eight patients received a further 2 weeks of treatment. Over the full 4 weeks, there was a reduction in HAMD scores of 62.2 ± 25.1 (1-Hz group) and 61.3 ± 25.2% (2-Hz group) (P > 0.05). Thirty of 63 (48%) patients in he 1-Hz group and 29 of 55 (53%) patients in 2-Hz group met response criteria (>50% reduction HAMD score) at study end. There was no difference in clinical response between groups.
Despite a heterogeneous sample, a significant proportion (˜50%) of patients met clinical response criteria following treatment. There was no difference in clinical response to 1- or 2-Hz rTMS applied to right dorsolateral PFC. This suggests that 2-Hz right PFC rTMS has antidepressant properties but offers no advantage over 1-Hz stimulation despite a twofold increase in pulse number.