Meta-analysis of randomized controlled trials examining social comparison as a behaviour change technique across the behavioural sciences

Research on social comparison as a behaviour change technique (SC-BCT) has increased substantially. We conducted a random-effects meta-analysis of randomized controlled trials investigating SC-BCTs across the behavioural sciences (PROSPERO: CRD42022343154). We searched MEDLINE, PsycINFO and Web of Science from inception to January 2024. Seventy-nine randomized controlled trials (N = 1,356,521) investigating effects on behaviours related to climate change mitigation, health, performance and service were included. In the short term (mean 3.7 months post-intervention), SC-BCTs produced small effects relative to both passive (Hedges' g = 0.17; 95% confidence interval, 0.11-0.23; k = 37; P < 0.001) and active control conditions (g = 0.23; 95% confidence interval, 0.15-0.31; k = 42; P < 0.001). A greater number of SC-BCT sessions and emphasis on desired (versus undesired) behaviours were associated with larger effects. Moderation effects were observed in only a few analyses, highlighting the need for further testing. SC-BCTs also produced significant small effects in the long term (mean 6.2 months post-intervention). Small effects should be interpreted in the context of low cost and scalability (for example, sending one or two emails). Certainty of evidence, using GRADE criteria, ranged from low to moderate depending on the analysis. More high-quality research is needed.