Published on in Vol 9 , No 5 (2021) :May
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/26152, first published
.

1 Department of Psychology, University of Pennsylvania, Philadelphia, PA, US
2 Bold Health Limited, UK, London, GB
3 Population Health Research Institute, St George’s University of London, London, GB