Therapeutic Effects of Transcranial Direct Current Stimulation in Obsessive-Compulsive Disorder: A Systematic Review

AbstractObsessive-compulsive disorder (OCD) is a chronic and disabling psychiatric condition characterized by intrusive obsessions and compulsive behaviors. Although pharmacotherapy and cognitive-behavioral therapy are first-line treatments, a significant proportion of patients remain treatment-resistant. Transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, has emerged as a potential adjunctive treatment by modulating dysfunctional neural circuits implicated in OCD. This systematic review aimed to critically evaluate the therapeutic efficacy, neural targets, and methodological rigor of multi-session tDCS interventions for OCD. A comprehensive literature search was conducted across PubMed, Scopus, ScienceDirect, and Web of Science up to March 2, 2025. Studies were included if they investigated multi-session tDCS or related transcranial electrical stimulation techniques in adults diagnosed with OCD. A total of 21 studies met the inclusion criteria and were analyzed for stimulation parameters, cortical targets, outcomes, and methodological quality. The review included 21 studies encompassing 672 participants with OCD. Most studies employed conventional tDCS protocols (2 mA, 20–30 minutes, 10–20 sessions), with fewer using HD-tDCS or tACS. Targeted brain regions included the pre-supplementary motor area (pre-SMA), orbitofrontal cortex, and dorsolateral prefrontal cortex (dlPFC), key nodes in the cortico-striato-thalamo-cortical circuit (CSTC) implicated in OCD. Many studies reported significant reductions in OCD symptom severity, especially when stimulating the pre-SMA and OFC. However, findings were heterogeneous, and several trials reported no significant difference between active and sham stimulation. Methodological limitations such as small sample sizes and variable designs were common. Nevertheless, tDCS was consistently well-tolerated across studies. Multi-session tDCS appears to be a promising and safe neuro-modulatory approach for reducing OCD symptoms, particularly when targeting the CSTC circuit. However, the variability in stimulation parameters, study designs, and outcome measures highlights the need for standardized protocols and large-scale randomized controlled trials. Future research should also explore individualized stimulation strategies guided by neurobiological and clinical markers to optimize efficacy.Keyword: Obsessive-compulsive disorder; transcranial direct current stimulation; treatment-resistant OCD; individualized treatment.