1 Faculty of Life Sciences and Medicine, King's College London, London SE1 9RT, UK. Electronic address: ella.burchill@kcl.ac.uk.
2 Division of Psychiatry, University College London, South London and Maudsley NHS Foundation Trust, London, UK.
3 Division of Pulmonary and Critical Care Medicine and Department of Physical Medicine and Rehabilitation, School of Medicine, John Hopkins University, Baltimore, MD, USA.
4 Edmond J Safra Program in Parkinson's Disease, University Health Network and the Department of Medicine, University of Toronto, Toronto, ON, Canada.
5 Institute of Psychiatry, Psychology, and Neuroscience, King's College London, London SE1 9RT, UK.