Jolande Van De Griendt ^1,2* Danielle Cath ^3,4 Agnes A. Wertenbroek ⁵ Cara W. Verdellen ⁶ Judith J. Rath ⁷ Irene Klugkist ⁸ Sebastiaan F. De Bruijn ⁹ Marc J. Verbraak ^1,10

• ¹ Behavioural Science Institute, Radboud University, Nijmegen, Netherlands
• ² TicXperts, Heteren, Netherlands
• ³ University Medical Center Groningen, Groningen, Netherlands, Netherlands
• ⁴ GGZ Drenthe, Assen, Netherlands
• ⁵ Ziekenhuis Groep Twente, Almelo, Netherlands
• ⁶ PsyQ Nijmegen, Nijmegen, Gelderland, Netherlands
• ⁷ LangeLand Hospital, Zoetermeer, Netherlands
• ⁸ Department of Methodology and Statistics, Faculty of Social and Behavioural Sciences, Utrecht University, Utrecht, Netherlands, Netherlands
• ⁹ Afdeling Neurologie, Haga Ziekenhuis, The Hague, Netherlands
• ¹⁰ Pro Persona, Arnhem, Netherlands

Introduction: The aim of this study was to directly compare behaviour therapy (exposure & response prevention; ERP) with pharmacotherapy (risperidone) with respect to tic severity and quality of life in patients with Tourette syndrome or tic disorders. Method: A total of 30 participants were randomly assigned to either ERP (12 weekly 1-hour sessions) or risperidone (flexible dosage of 1-6 mg) with follow-up at 3 and 9 months after end of treatment. Outcome measures included tic severity as measured by the Yale Global Tic Severity Scale, quality of life and side effects. Predefined informative hypotheses were evaluated using Bayes factors (BF), a Bayesian alternative for null hypothesis testing with p-values, that provides a more reliable and powerful method in the case of small samples. A BF larger than one indicates support for the informative hypothesis and the larger the BF, the stronger the support, with a BF between 3 and 10 being considered to provide moderate evidence. Results: Both ERP and Risperidone were found to be effective with respect to tic severity at end of treatment (BF 5.35). At 9 months follow-up, results remained stable (BF 4.59), with an advantage of ERP over Risperidone at 3 months follow-up (BF 3.92). With respect to quality of life, an effect was found for ERP (BF 3.70 at 3 months follow up; BF 3.08 at 9 months follow-up). Dropout rates were higher in the medication condition, mainly due to significantly more side effects halfway during treatment, fading out towards end of treatment. Discussion: Behaviour therapy and medication are equally viable options in the treatment of tic disorders, with a slight preference for ERP based on follow-up results on tic severity and quality of life, and side effects.