Lack of a therapeutic effect of a 2-week sub-threshold transcranial magnetic stimulation course for treatment-resistant depression.

Stimulation parameters seem to strongly influence the efficacy of repetitive transcranial magnetic stimulation (rTMS) in the management of treatment-resistant depressed patients. The most effective and safest parameters are yet to be defined. Moreover, systematic follow-up data available to document the duration of the therapeutic effects remain sparse. Twenty-one treatment-resistant depressed patients were randomized to either active rTMS (N=12) or to sham (N=9) treatment in a double-blind design. Patients were kept on their medications. Sub-motor-threshold (MT) stimulation (80% MT) was delivered for 10 consecutive work days (20 Hz, 2-s trains, 20 trains). Subjects meeting pre-set criteria for responding were entered into a follow-up phase for up to 5 months. Utilizing the above stimulation parameters, we found no significant difference between groups. Six patients in the active group and one subject in the sham group met criteria for the follow-up phase. The period of time before subjects met criteria for relapse was highly variable ranging from 2 to 20 weeks. Sub-threshold rTMS stimulation for 2 weeks is not significantly superior to sham treatment for treatment-resistant depressed patients. The duration of the therapeutic effects of rTMS delivered to the left prefrontal cortex using the above-described parameters is highly variable.