Rationale:~Obsessive-compulsive disorder (OCD) is a serious and disabling mental disorder, characterized by obsessions and compulsions and associated with substantial comorbidity and morbidity (Stein et al. 2019). Approximately 50% of patients treated with standard treatments (exposure therapy with response prevention (ERP) with/without medication) fail to respond fully, resulting in chronicity and poor participation in social and educational/occupational domains. We propose to fill the gap between the standard treatments (exposure therapy with/without medication) on the one side and invasive end-stage strategies (brain surgery) on the other side, using a non-invasive alternative: repetitive transcranial magnetic stimulation (rTMS). Despite proven efficacy (Zhou et al. 2017; Rehn et al. 2018; Fitzsimmons et al. 2022), rTMS for OCD is not yet covered by the Dutch insurance system while rTMS for treatment resistant depression is. This multi-center randomized controlled trial, supported by the 'veelbelovende zorg' grant of Zorg Instituut Nederland (ZIN), aims to establish the added value of rTMS applied over the pre-supplementary motor area (preSMA) when combined with ERP in OCD patients, who show no/insufficient response to ERP (alone or combined with medication). In case of proven cost-effectiveness it will lead to the addition of rTMS as insured health care for patients with OCD.~Objective: assess the (cost-)effectiveness of 1Hz rTMS to the pre-SMA as adjuvant treatment to ERP in OCD patients who show no/insufficient response to ERP (alone or combined with medication)~Study design: multi-center placebo-controlled double-blind randomized controlled trial with an intervention phase of 5-7 weeks and a follow-up phase of 12 months~Study population: 250 adult (18 years and older) OCD patients who show no/insufficient response to ERP~Intervention (if applicable): Low frequency (1 Hz) rTMS to the pre-SMA (compared to sham rTMS to the pre-SMA) as adjuvant treatment to ERP, 4 times/week for at least 5 weeks (20 sessions), with optional extension phase of 1 or 2 weeks (maximum of 28 sessions in total)~Main study parameters/endpoints: the pre-versus-post-treatment standardized mean difference (SMD) in severity of OCD (Yale-Brown Obsessive-Compulsive Scale - Y-BOCS), version 2. The post-treatment Y-BOCS score will be obtained at the end of treatment, i.e, after 20, 24 or 28 sessions.~Secondary study parameters/endpoints:~Response (≥35% reduction on Y-BOCS-v2) and remission (Y-BOCS≤12) as established through international expert opinion~Standard Mean Difference (SMD) on the Clinical Global Impression (CGI) severity scale~Clinical Global Impression (CGI) improvement scale~Quality of life (EQ-5D-5L)~Societal costs, measured through the iMTA Productivity Cost Questionnaire (iPCQ) and the iMTA Medical Consumption Questionnaire (iMCQ)~Depression, measured using the Beck Depression Inventory (BDI) at baseline, post-treatment and follow-up. In addition we will administer a visual analogue scale (VAS) for depression at these same time points, plus every week during treatment, to monitor the effects of treatment on severity of depressive symptoms.~Anxiety, measured using the Beck Anxiety Inventory (BAI) and a VAS; following the same procedure and rationale as for depression.~Tolerability of the treatment and side effects, using an in-house questionnaire~Exploratory outcomes and/or influencing factors:~Patient adherence to treatment protocol, as measured using the Patient Exposure and Response Prevention Adherence Scale (PEAS)~Difference between responders and non-responders on circadian rhythm and sleep disorders at baseline as defined by the Holland Sleep Disorders Questionnaire (HSDQ).~Structural brain network characteristics (using T1 and diffusion weighted scans) to predict treatment response / relapse.~Functional resting-state and task-based (during emotional processing) brain network characteristics (using echo-planar imaging) to predict treatment response / relapse.~Variation in the exact stimulation location as ascertained and recorded by neuronavigation in relation to treatment outcome.~Contribution of demographic and clinical variables (sex, age, medication status) and pre-existing comorbidities (i.e. comorbid tics, depression, anxiety, autism) to the variance in treatment outcome.~In OCD patients with comorbid tics: tic severity, measured using the Yale Global Tic Severity Scale (Y-GTSS).~Variation in treatment expectancy (7-items credibility and expectancy questionnaire (CEQ)) and blinding success (1-item question 'in which condition do you think you were?') in relation to treatment outcome.
TETRO is a multi-center placebo-controlled double-blind randomized controlled trial with an intervention phase of 5-7 weeks and a follow-up phase of 12 months in 250 adult (18 years and older) OCD patients who show no/insufficient response to ERP, aiming to establish the cost-effectiveness of low frequency (1 Hz) rTMS to the pre-SMA (compared to sham rTMS to the pre-SMA) as adjuvant treatment to exposure with response prevention (ERP). The treatment consists of 4 times/week rTMS combined with ERP for at least 5 weeks (20 sessions), with optional extension phase of 1 or 2 weeks (maximum of 28 sessions in total).