JMIR Publications

ABSTRACT

Background:

Group chats on platforms such as WhatsApp, WeChat, and Telegram are central to everyday communication in many settings, including across low-middle-income countries and among groups often overlooked by one-to-one or app-based digital health tools. They can rapidly circulate information and sustain peer interaction, with growing observational evidence of their influence on health communication. Yet their effectiveness and underlying mechanisms as intentional health interventions have never been systematically examined.

Objective:

This systematic review and realist synthesis evaluated the effectiveness of group chat-based health interventions and explained mechanisms and contextual conditions shaping their outcomes. It mapped intervention characteristics and effects and identified Context Mechanism Outcome configurations driving behaviour change.

Methods:

We included studies that used group chats as primary delivery channels, spanning randomized controlled trials (RCTs) and other interventional designs. Searches of PubMed, Embase/MEDLINE, Web of Science, and Scopus (2005-2025) and reference screening identified eligible studies. RCT quality was assessed with the RoB 2 tool. For the realist synthesis, Context Mechanism Outcome configurations were extracted and analyzed using reflexive thematic analysis informed by Social Cognitive Theory and synthesized into a final programme theory.

Results:

75 studies met inclusion criteria for the realist synthesis, of which 27 RCTs were also included in the systematic review. Studies were conducted mainly in Asian settings and the United States and targeted maternal and child health, chronic disease management, mental health, and lifestyle behaviours. Among the 27 RCTs, 13 (48%) reported positive effects, 9 (33%) mixed effects, 4 (15%) neutral findings, and 1 (4%) negative effect; 15 (55.6%) had low risk of bias. Improvements were most evident for self management and psychosocial outcomes, with more variable effects on clinical indicators. The realist synthesis identified 12 recurring CMO configurations across five domains: capability and actionability, confidence and motivation, modelling and norms, safe and supportive environment and access, and self regulation and maintenance. These mechanisms were activated or suppressed by facilitation quality, group composition, cultural alignment, technological access, and social norms. The final programme theory depicts group chats as dynamic systems where access, facilitation, and group structure shape how the domains amplify or dampen one another, explaining shifts from low engagement to high trust spaces that sustain behaviour change.

Conclusions:

This review positions group chats as a distinct pillar of digital health rather than an auxiliary feature. Realizing their potential requires treating them as designed social environments, with investment in facilitation, equity oriented access, and attention to norms and power dynamics. The programme theory highlights leverage points for researchers, implementers, and funders to embed group chats within health systems so that existing messaging ecologies are harnessed for scalable and equitable health support. Clinical Trial: PROSPERO CRD420251082787; https://www.crd.york.ac.uk/PROSPERO/view/CRD420251082787