Effects of transcranial direct current stimulation (tDCS) at different cortical targets on cognition in obsessive-compulsive disorder (OCD): an exploratory analysis

: Transcranial direct current stimulation (tDCS) holds promise as a treatment for obsessive-compulsive disorder (OCD). Patients with OCD show impairment in specific domains of cognitive flexibility and response inhibition. We previously reported that tDCS produced a positive clinical effect on OCD symptoms. Here, we report a secondary analysis of neurocognitive data. In this randomized, double-blind, sham-controlled, crossover, multicenter feasibility study, adults with a diagnosis of OCD according to the diagnostic and statistical manual of mental disorders, fifth edition (DSM-5) received three courses of clinic-based tDCS, targeting the left orbitofrontal cortex (L-OFC), bilateral supplementary motor area (SMA), and sham, randomly allocated and delivered in counterbalanced order. Cognitive assessments were conducted before and 2-h after the first stimulation in each arm. Nineteen adults were recruited. tDCS of both the L-OFC and SMA significantly improved cognitive inflexibility, while sham treatment did not (paired-sample t test, baseline vs. 2-h after stimulation). No significant effect of tDCS was found for motor impulsivity (stop-signal reaction time) in any of the three arms. In a small sample of patients with OCD, a single administration of tDCS to the L-OFC and SMA produced a rapid improvement in cognitive inflexibility but not in motor impulsivity. A definitive randomized, controlled trial of tDCS targeting both the OFC and SMA, including cognitive markers, is indicated.