Intended for healthcare professionals

Primary Care

Health related virtual communities and electronic support groups: systematic review of the effects of online peer to peer interactions

BMJ 2004; 328 doi: (Published 13 May 2004) Cite this as: BMJ 2004;328:1166
  1. Gunther Eysenbach (geysenba{at}, associate professor1,
  2. John Powell, senior lecturer2,
  3. Marina Englesakis, information specialist3,
  4. Carlos Rizo, PhD candidate4,
  5. Anita Stern, PhD candidate4
  1. 1Department of Health Policy, Management and Evaluation, University of Toronto, Centre for Global eHealth Innovation, University Health Network, Toronto General Hospital, Fraser Elliott Bldg, 190 Elizabeth St, Toronto, ON, Canada M5G 2C4
  2. 2Wessex Institute for Health Research and Development, University of Southampton, Southampton SO16 7PX
  3. 3Library, University Health Network, Toronto General Hospital
  4. 4Centre for Global eHealth Innovation, University Health Network, Toronto General Hospital
  1. Correspondence to: G Eysenbach
  • Accepted 21 April 2004


Objective To compile and evaluate the evidence on the effects on health and social outcomes of computer based peer to peer communities and electronic self support groups, used by people to discuss health related issues remotely.

Design and data sources Analysis of studies identified from Medline, Embase, CINAHL, PsycINFO, Evidence Based Medicine Reviews, Electronics and Communications Abstracts, Computer and Information Systems Abstracts, ERIC, LISA, ProQuest Digital Dissertations, Web of Science.

Selection of studies We searched for before and after studies, interrupted time series, cohort studies, or studies with control groups; evaluating health or social outcomes of virtual peer to peer communities, either as stand alone interventions or in the context of more complex systems with peer to peer components.

Main outcome measures Peer to peer interventions and co-interventions studied, general characteristics of studies, outcome measures used, and study results.

Results 45 publications describing 38 distinct studies met our inclusion criteria: 20 randomised trials, three meta-analyses of n of 1 trials, three non-randomised controlled trials, one cohort study, and 11 before and after studies. Only six of these evaluated “pure” peer to peer communities, and one had a factorial design with a “peer to peer only” arm, whereas 31 studies evaluated complex interventions, which often included psychoeducational programmes or one to one communication with healthcare professionals, making it impossible to attribute intervention effects to the peer to peer community component. The outcomes measured most often were depression and social support measures; most studies did not show an effect. We found no evidence to support concerns over virtual communities harming people.

Conclusions No robust evidence exists of consumer led peer to peer communities, partly because most peer to peer communities have been evaluated only in conjunction with more complex interventions or involvement with health professionals. Given the abundance of unmoderated peer to peer groups on the internet, research is required to evaluate under which conditions and for whom electronic support groups are effective and how effectiveness in delivering social support electronically can be maximised.


  • Embedded ImageTables A-D and appendixes 1-3 are on

  • Contributors GE and JP have contributed equally to the study and are joint guarantors. GE wrote the first drafts of the protocol and the manuscript including all online tables, coordinated the research, and obtained funding; JP and AS compiled tables 1 and 2; GE and CR developed the extraction database; CR and AS coordinated obtaining the papers. GE, JP, AS and CR participated in the protocol development, screened abstracts, abstracted papers (GE and JP 15 each, AS 11, CR 7), and revised manuscript drafts. ME developed the search strategies and conducted the searches. ME, AS and CR are listed alphabetical, with the order of authors not necessarily reflecting their contribution

  • Competing interests None declared.

  • Note about process While GE has the same departmental affiliation and works (with AS and CR) in the same centre as Alejandro Jadad, guest editor of this theme issue, it was submitted to the BMJ in the normal way, and Jadad neither played any part in the decision making over this paper, nor was he involved in conception or conduct of this study.

  • Accepted 21 April 2004
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