- Correspondence to Professor Nir Eyal, Department of Global Health and Population, Harvard T. H. Chan School of Public Health, FXB Building, 7th floor, 651 Huntington Ave., Boston, MA 02115, USA;
- Received 14 November 2015
- Revised 28 January 2017
- Accepted 6 March 2017
- Published online 10 April 2017.