Investigating the Acceptability and Tolerability of tDCS in Patients with OCD - A Feasibility Study

Abstract

Introduction: Obsessive Compulsive Disorder (OCD) is a neuropsychiatric disorder which often proves refractory to current treatment approaches1. Transcranial Direct Current Stimulation (tDCS), a non-invasive form of neurostimulation, with potential for development as a self-administered intervention, has shown potential as a safe and efficacious treatment for OCD in a small number of trials2. The two most promising stimulation sites are located above the orbitofrontal cortex (OFC) and the supplementary motor area (SMA). The aim of this feasibility study was to inform the development of a definitive trial, focussing on the acceptability, safety of the intervention, feasibility of recruitment, adherence and tolerability to tDCS and study assessments and the size of the treatment-effect. Due to COVID-19 this study was paused in March 2020 and restarted in July 2020, consequently facing the challenges of recruiting and continuing face-to-face research during the pandemic. This abstract presents acceptability and safety of the intervention as well as the feasibility of recruitment, adherence and tolerability of tDCS in patients with OCD. Method: Potential participants were identified from OCD clinics, primary health care services (e.g. IAPTs), charity/support networks, advertisements and trust databases across two sites (Hertfordshire Partnership and Southampton). Individuals were screened, then randomised if eligible, receiving three courses of tDCS (SMA, OFC and sham), randomly allocated and given in counterbalanced order. Each course comprised four sessions of 20-minute stimulations, delivered over two consecutive days, separated by at least a four-week washout period. Participants were evaluated at baseline, 1, 2 and 4 hours after stimulation. Follow-up assessments were conducted via telephone at 24 hours, 7 and 14 days following the last stimulation of each round with a final assessment 28 days after the third round. Intervention-related adverse events (AEs) were also recorded at each time point, using a questionnaire specific to tDCS3. Results: A total of 135 individuals were identified as potentially eligible (through clinics or self-referral), of which 36 consented to eligibility screening. Four withdrew consent/were lost to follow up, so screening was completed for 32. Subsequently, 16 were excluded through ineligibility (n=9), withdrawal (n=2) or loss to follow up (n=1), with the remaining 20 randomised. One participant withdrew prior to intervention round one and another prior to round two, both due to COVID-19 anxiety. All other participants (n=18, 90% of those randomised) completed all three intervention rounds. However, one individual was unable to attend day two of round two due to unconnected ill-health. Across all tDCS types, the most commonly reported AEs were sleepiness (18.7% of sessions), trouble concentrating (13.0%) and headache (12.2%), with other AE types present at <7% of sessions. Itching (0.8%) and scalp pain (1.0%) were reported least often. Discussion: Despite the impact of COVID-19, this study successfully restarted after suspension with few adjustments, meeting the revised target sample with minimal participant drop-out. Reasons for drop-out were unrelated to the intervention itself, with some participants delayed or experiencing pandemic-related anxiety. This study presents a safe intervention which was accepted, adhered to and tolerated by OCD patients, even amid a pandemic.