Hoddinott et al. BMC Public Health 2010, 10:800 http://www.biomedcentral.com/1471-2458/10/800 beliefs and behaviours than the individual group participants [9]. Conclusion The evidence for effectiveness and cost-effectiveness of group compared with one-to-one interventions for health improvement is weak or unknown. Health improvement or behaviour change interventions delivered in a group setting are complex adaptive social processes with inter- actions between the group leader, participants, and the wider community and environment. As with any complex intervention, there is a need to understand which aspects of group processes work, for whom, how and in what cir- cumstances. Ecological models of behavioural change may be more appropriate than applying theories of indi- vidual behavioural change in a group setting. This frame- work is the first step towards advocating a more systematic approach to designing, evaluating and report- ing interventions in group settings, which is necessary to improve the currently weak evidence base. Acknowledgements The Chief Scientist’s Office of the Scottish Government Health Directorate provided funding for PH through a Primary Care Research Career Award and AA through a Career Scientist Award. The Health Services Research Unit, University of Aberdeen, is funded by the Chief Scientist Office of the Scottish Government Health Directorates. The views expressed are those of the authors. Author details 1Health Services Research Unit, University of Aberdeen, Health Sciences Building, Foresterhill, Aberdeen AB25 2ZD, UK. 2NHS Education for Scotland, Thistle House, 5th Floor, 91 Haymarket Terrace, Edinburgh, EH12 5HD, UK. 3Centre for Rural Health, University of Aberdeen, The Centre for Health Science, Old Perth Road, Inverness, IV2 3JH, UK. 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