Efficacy of pre-supplementary motor area transcranial direct current stimulation for treatment resistant obsessive...

A significant proportion of obsessive compulsive disorder (OCD) patients do not respond to specific serotonin reuptake inhibitors (SSRIs). There is a need to evaluate novel treatment options for OCD.

In this double blinded, randomized, sham controlled study, we investigated the efficacy of add-on transcranial direct current stimulation (tDCS) in reducing the symptoms in SSRI-resistant OCD patients by employing anodal pre-supplementary motor area (pre-SMA) stimulation.

Twenty-five patients with DSM-IV OCD having persistent symptoms despite adequate and stable treatment with at least one SSRI were randomly allocated to receive 20 min of verum (active) 2-mA tDCS or sham stimulation twice daily on 5 consecutive days [anode over Pre-SMA; cathode over right supra-orbital area]. Response to treatment was defined as at least 35% reduction in the Yale-Brown Obsessive-Compulsive Scale (YBOCS) total score along with a Clinical Global Impression - Improvement (CGI-I) score of 1 (very much improved) or 2 (much improved).

The response rate was significantly greater in the verum tDCS(4 out of 12) compared to sham-tDCS (0 out of 13) [Fisher's exact test, p = 0.04]. Repeated measures analysis of variance with tDCS type (verum vs. sham) as between subjects factor showed that there was a significant tDCS-type X time-point interaction with significantly greater reduction of YBOCS total score [F (1,22) = 4.95,p = 0.04,partial-η² = 0.18] in verum-tDCS group.

The results of this RCT suggest that tDCS may be effective in treating SSRI-resistant OCD. Future studies should examine the efficacy in larger samples of OCD and explore other potential target regions using randomized sham-controlled designs, in addition to examining the sustainability of the beneficial effects.

Clinical Trials Registry India (http://ctri.nic.in/Clinicaltrials/login.php): Registration Number- CTRI/2016/04/006837).