Received: 24 June 2019
Accepted: 1 November 2019
First Online: 21 January 2020
Ethics approval and consent to participate
: Not applicable (systematic review of previously published data).
: Not applicable (no individual information or data presented).
: Amanda Bunten, Lucy Porter and Natalie Gold work for Public Health England Behavioural Insights (PHEBI). Amanda Bunten is second author of one of the studies included in the review.