Table 1

Categories of research evidence applied to statements (adapted from Buckley et al)73

 ARandomised, controlled trials (RCTs)Data are overwhelmingly from RCT studies, and findings are consistent.
 BRCT (limited data) and high-quality observational dataFew RCTs exist; they have small sample sizes and/or results are inconsistent. AND/OR
Observational studies supported by evidence of causality from laboratory-based or experimental studies.
 CNon-RCTs, observational studiesOutcomes are from uncontrolled, non-randomised and/or observational studies (overwhelmingly cross-sectional).
 DExpert consensusEvidence is insufficient for categorisation in A–C; panel’s expert opinion.