Placebo Effect After Prefrontal Magnetic Stimulation in the Treatment of Resistant Obsessive-compulsive Disorder: a Randomized Controlled Trial

Many patients with obsessive-compulsive disorder (OCD) do not achieve satisfactory symptom improvement with conventional treatments. Here, we evaluate the efficacy of repetitive transcranial magnetic stimulation (rTMS) applied over the right dorsolateral prefrontal cortex (rDLPFC) in patients with treatment-resistant OCD. This was a double-blind randomized trial involving 30 treatment-resistant OCD outpatients, allocated to have either sham or active high-frequency rTMS (over the rDLPFC) added to their treatment regimens for 6 wk, with 6 wk of follow-up. Active rTMS consisted of 30 applications (figure-of-eight coil; 10 Hz at 110% of motor threshold; 1 session/d; 40 trains/session; 5 s/train; 25-s intertrain interval). At weeks 0, 2, 6, 8, and 12, we applied the Yale-Brown Obsessive-Compulsive Scale (YBOCS), Clinical Global Impression (CGI) scale, 14-item Hamilton Anxiety Rating Scale (HAMA-14), 17-item Hamilton Depression Rating Scale (HAMD-17), and 36-item Short-form Health Survey. The primary outcome measure was a positive response (≥ 30% improvement in YBOCS score, together with a 'much improved' or 'very much improved' CGI - Improvement scale rating). One patient in each group showed a positive response (p=1.00). For YBOCS score, there was significant effect of time (F=7.33, p=0.002) but no significant group effect or group×time interaction. In treatment-resistant OCD, active rTMS over the rDLPFC does not appear to be superior to sham rTMS in relieving obsessive-compulsive symptoms, reducing clinical severity, or improving treatment response, although there is evidence of a placebo effect.