Investigating the Efficacy of Transcranial Alternating Current Stimulation in the Treatment of Obsessive-Compulsive Disorder (tACS-OCD)

Transcranial Alternating Current (tACS) is a form of non-invasive brain stimulation that delivers a weak electrical current that alternates at a specified frequency back and forth between electrodes. The tACS device in this trial (BrightStim2) consists of a purpose-built handheld battery driven unit that delivers a current controlled voltage across an active and reference electrode. The active and reference electrodes are placed within commercially supplied saline soaked sponges. We have developed this device within our research team to produce the same effects as existing commercial devices but to be programmable in a manner that the research team can preset the conditions of use with no capacity for the patients to alter this or use the device in a manner outside of our research protocol. To date, there have been hundreds of studies of tACS, including in people with depression, conducted internationally. There have been no issues or problems reported in these studies over and above the known side effects. The BrightStim stimulator was used in our pilot study (ACTRN12620000748910) that assessed the efficacy of tACS in OCD. It has also been used in other experimental studies with involving patients and healthy controls, and has also been demonstrated to produce effects equivalent to those produced with a widely commercially available device in a structured assessment. No safety or other issues/problems arose in any of these studies. Mode of action: polarisation of neurons via mild electrical current Dosage Regime: tACS will be applied targeting the medial prefrontal cortex with a placement of electrodes at the AFz and Iz positions. Individualised alpha frequency (IAF) will be determined for all participants through a pre-treatment electroencephalography (EEG) session and stimulation will occur at this frequency. Each tACS session will last 30 minutes (continuous) with stimulation intensity of 1.5mA. Study Design: The study will be in the form of a randomised, double-blind, sham-controlled parallel two-arm clinical trial with an open-label crossover phase offered to the sham group. This study has been designed according to SPIRIT Guidelines and will follow reporting of results in agreement with the international CONSORT Guidelines. Treatment will occur over a six-week period in both the initial and cross over study phases. During the first three weeks, participants will receive treatment twice daily (intensive treatment phase), 5 days per week (with a break of 2 days each week). In the subsequent three weeks, they will receive treatment once daily, three days per week (consolidation phase). After this, they will be followed up for three months to evaluate whether they have achieved treatment persistent benefits. After this time, in the open label crossover phase, participants who initially received sham will receive active tACS for 6 weeks with intensive (3 weeks) and consolidation phases (3 weeks) as before. The initial active group will continue to be followed up every 3 months for 1 year post-treatment. Administration of intervention: The first treatment of each participant will be administered under direct supervision of an experienced investigator. After training on self-administration, and once each participant has demonstrated that they can implement the stimulation independently, participants will be permitted to administer treatments at home. Additional remote supervision and support will be provided via video and telephone communication. The tACS devices are programmed to save a log of the delivered treatments, which could be accessed by the investigator to monitor adherence. Additionally, participants are requested to maintain a log of all administered treatments.