1 Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK; South London and Maudsley NHS Foundation Trust, Denmark Hill, London SE5 8AZ, UK. Electronic address: brendon.stubbs@kcl.ac.uk.
2 Department of Rehabilitation Sciences, KU Leuven, Leuven, Belgium; University Psychiatric Center, KU Leuven, Kortenberg, Belgium.
3 Cambridge Centre for Sport and Exercise Sciences, Anglia Ruskin University, Cambridge, UK.