Box 6 Included studies and appraisal checklists.

Study design	Appraisal checklists
Randomised controlled trial (n = 3)	SIGN and CASP
Cluster randomised controlled trial (n = 1)	SIGN and CASP
Quasi‐randomised controlled trial (n = 3)	SIGN and CASP
Retrospective case control study (n = 1)	SIGN and CASP
Cross‐sectional study (n = 3)	SIGN and NZGG
Non‐comparative descriptive study (n = 7)	Reviewer checklist
Non‐comparative time series study (n = 1)	Reviewer checklist
Qualitative study (n = 13)	CASP and UKGCSRO

CASP, Critical appraisal skills programme⁴¹; SIGN, Scottish intercollegiate guidelines network⁴²; NZGG, New Zealand guidelines group⁴³; UKGCSRO, UK Government chief social researcher's office.⁴⁴

Reviewer checklist included: purpose, population, response rate, outcome definition and assessment.