Limited efficacy of 3 mA intensified tDCS of the right inferior frontal cortex for OCD treatment: A randomized, sham-controlled study

ObjectiveTranscranial direct current stimulation (tDCS) has been proposed for treating obsessive-compulsive disorder (OCD). While it has advantages such as affordability, home-use application, and fewer side effects compared to other treatment options, its clinical efficacy is not yet established, and previous results have been mixed. This randomized, sham-controlled study investigated the efficacy of a novel intensified tDCS protocol targeting the inferior frontal cortex (IFC), a relevant brain region for inhibitory control, for OCD treatment. MethodsForty patients with OCD received 20 sessions of 3 mA intensified tDCS or sham tDCS in randomized parallel groups. The active treatment included 20 sessions of 20-minute 3 mA stimulation delivered twice per day (in 2 weeks) with 20-min between-session intervals (i.e., intensified). Intervention efficacy and treatment response were evaluated before and after the intervention and at two-week, 1-month, and 3-month follow-ups. Cognitive functions (response inhibition, cognitive flexibility, and sustained attention) were also assessed at these time points. Side effects rating and blinding efficacy were evaluated across groups. ResultsDespite higher-rated side effects in the active tDCS group, blinding of patients was successful. OCD symptoms, anxiety, and depression decreased over time in both groups. Despite a significant post vs. pre-intervention reduction of all clinical measures only in the active tDCS group, no statistically significant differences emerged in the active vs sham conditions. The mean change in the OCD symptoms from baseline to the study endpoint and number of responders ([≥]50% symptom reduction) were 22.38% and 20% (4/20) in the active tDCS and 15.25% and 0.0 (0/20) in the sham tDCS groups. Similarly, cognitive assessments of sustained attention, cognitive flexibility, and response inhibition showed within-group improvements over time but no group-specific effects. ConclusionsThe 3 mA intensified tDCS over the right IFC showed limited efficacy confounded with placebo effects for OCD treatment.