New interventions are needed for obsessive-compulsive disorder. Here we present a randomized single-blinded, two-arm, parallel-group, sham-controlled clinical trial assessing the efficacy of prefrontal cortex stimulation in reducing obsessive-compulsive disorder symptoms and frontostriatal connectivity (ACTRN12616001687482). Conducted at a single academic center, the trial enrolled participants diagnosed with obsessive-compulsive disorder who underwent baseline clinical assessments and neuroimaging. The intervention comprised 20 weekday sessions of neuronavigated continuous theta burst stimulation of the frontal pole or sham. Participants and all staff assessing intervention outcomes were blind to the conditions. We enrolled a sample of 50 individuals (26 active continuous theta burst stimulation) who completed the neuroimaging and clinical assessments at the primary 4 week endpoint. Clinical data at the secondary 6 month endpoint were obtained from 46 participants (23 active). Symptoms of obsessive-compulsive disorder (primary outcome) decreased in both groups (active −4.35, P < 0.001; sham −5.92, P < 0.001), but there was no significant difference between groups (P = 0.33, η_p² = 0.02). Likewise, there was no significant difference between groups in changes of frontal pole connectivity with the striatum (P = 0.09, η_p² = 0.06). Changes in secondary outcomes (symptoms of anxiety and depression and localized frontal pole activity) did not differ between groups. Dropout rates did not vary between groups and the most common treatment-related adverse event in both groups was headache. Our findings suggest that frontal pole continuous theta burst stimulation is no different to sham in reducing obsessive-compulsive disorder symptoms. The absence of changes in brain activity prompts further evaluation of alternative stimulation protocols.

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