1. National Center of Epidemiology and CIBERNEDCarlos III Institute of Health Madrid Spain
2. Department of Clinical Neurosciences, Royal Free Campus Institute of NeurologyUniversity College London London United Kingdom
3. Departments of Psychiatry and NeurologyPerelman School of Medicine at the University of Pennsylvania Philadelphia Pennsylvania USA
4. Parkinson's Disease ResearchEducation and Clinical Center (PADRECC), Philadelphia Veterans Affairs Medical Center Philadelphia Pennsylvania USA
5. Parkinson's Foundation International Centre of ExcellenceKing's College Hospital London United Kingdom
6. Institute of Psychiatry, Psychology and NeuroscienceKing's College London London United Kingdom