The effects of repetitive transcranial magnetic stimulation on depressive symptoms and the P300 event-related potential

Changes in the Hamilton Depression Rating Scale and the P-300 auditory event-related potential were assessed in 10 patients with depression before and after a treatment course of five daily sessions of 10 Hz repetitive transcranial magnetic stimulation ( rTMS) over the left prefrontal cortex. The patients were initially randomly allocated either to an active or a placebo rTMS treatment. All patients received both types of treatment separated by an interval of 4 weeks. The median Hamilton score decreased by 7 points following active rTMS and by 1 point after sham ( p = 0.075). Active rTMS was associated with a significant increase in the P300 amplitude compared with sham ( p = 0.02). There was no correlation between changes in P300 measurements and the Hamilton scores after active treatment. We conclude that five daily sessions of left prefrontal rTMS treatment is not of sufficient duration to make a significant improvement in depressive symptoms.