Competing interests: KRM-V has non-financial competing interests as a member of the medical advisory board of the Tourette Association America (TAA), the scientific advisory board of the German Tourette Association (TGD), the board of directors of the German (ACM) and the International (IACM) Association for Cannabinoid Medicines, and the committee of experts for narcotic drugs at the federal opium bureau of the Federal Institute for Drugs and Medical Devices (BfArM) in Germany; has received financial or material research support from the EU (FP7-HEALTH-2011 no. 278367, FP7-PEOPLE-2012-ITN no. 316978), the German Research Foundation (DFG: GZ MU 1527/3-1), the German Ministry of Education and Research (BMBF: 01KG1421), the National Institute of Mental Health (NIMH), the Tourette Gesellschaft Deutschland e.V., the Else-Kroner-Fresenius-Stiftung, and GW, Almirall, Abide Therapeutics, and Therapix Biosiences; has served as a guest editor for Frontiers in Neurology on the research topic “The neurobiology and genetics of Gilles de la Tourette syndrome: new avenues through large-scale collaborative projects”, is an associate editor for Cannabis and Cannabinoid Research and an Editorial Board Member of Medical Cannabis and Cannabinoids; has received consultant’s honoraria from Abide Therapeutics, Tilray, Resalo Vertrieb GmbH and Wayland Group, speaker’s fees from Tilray, and royalties from Medizinisch Wissenschaftliche Verlagsgesellschaft Berlin, Elsevier and Kohlhammer; and is a consultant for Nuvelution TS Pharma Inc., Zynerba Pharmaceuticals, Resalo Vertrieb GmbH, CannaXan GmbH, Therapix Biosiences and Columbia Care.