Hoddinott et al. BMC Public Health 2010, 10:800 http://www.biomedcentral.com/1471-2458/10/800 Table 3: What happens within a group (Continued) ○ How cohesive is the group? ○ How much communication between group members occurs? Minimal, mostly non-verbal to in depth engagement? ○ Is communication within the group channelled through the leader, within subgroups or free with multiple conversations? How will the group influence people? This is a contentious area as no single theory can cap- ture the complexity of intra and inter group behaviour. In Table 2, we suggest separating the social and beha- vioural theories that inform the group intervention from the theory of how the group itself is likely to influence the attitudes, beliefs and behaviours of participants. Individual behaviour change theories and techniques have been reviewed [40], but not specifically for delivery in group settings and it cannot be assumed that they are generalisable, as individuals can behave differently when in a group [9]. Group composition may have a causal effect on group outcomes; the group may be the social context which allows other inter-personal psychological phenomena to unfold or group composition may be a consequence of other external factors [41]. How intra and inter group processes influence peo- ple’s attitudes, beliefs and behaviours are reviewed else- where [9], although not specifically in the context of health improvement. In Table 2 we provide some exam- ples of theories which are particularly relevant to health improvement group interactions. Festinger’s Social Comparison Theory [42] proposes that conformity within a group is dependent on three main motivations: dependence on others for information to self-evaluate; achieving group goals and the need for approval and a desire not to seem different. Festinger hypothesises that group participants will try to improve their performance and will differ in whether they compare upwards or downwards, for similarities or dissimilarities. They will select different attributes to compare, which may not always be the expected ones [20]. Downward compari- son where a person wants to know how dissimilar he/ she is from the most undesirable person is more com- mon in the expert patient programme and serves to pro- tect a threatened self-esteem [27]. Festinger hypothesises that high status members are motivated to try and improve the performance of others less capable or they might perform below their capability so that they would not appear too different from the rest. Criticisms are that social comparison theory focuses on intra-group comparisons, whereas temporal comparisons with the past or the future, or comparisons with other groups or non group participants may be of equal importance [9]. Social support theory proposes that information is dis- seminated more effectively between networks of people with strong social ties and this confers health benefits Page 6 of 9 [43]. In groups, strong and weak social connections may differ in their effects and either reinforce existing atti- tudes and behaviours or mediate change. Influence often extends beyond the group to the family, local community or population and this may be intentional, for example in peer education interventions, or unintentional. This poses challenges for outcome measurement and contami- nation, as the cumulative outcome is the sum of the indi- vidual outcomes and the collateral positive or negative health outcomes of others [44]. There is a continuing debate about the relative importance of social support network size and the strength of connections. On-line support groups are becoming increasingly popular and provide large networks of relatively superficial support [28]. Further comparisons between actual and virtual health improvement and support groups are warranted. Bandura’s Social Learning Theory with its emphasis on learning through observation and modelling beha- viour [45] is particularly relevant to behaviours involving action or performing, like breastfeeding or parenting skills [20]. Minorities and majorities both influence group processes and Social Impact Theory proposes a negatively accelerating continuum of influence based on observations that the first social stimulus has the great- est effect, the second less effect and the third less still [46]. What are the health outcomes and target populations? Outcomes from interventions delivered in a group are usually measured at the individual level [1-3], and most studies do not consider interactions between patients in the same group which may lead to correlation of out- comes [13]. Cluster randomized controlled trials where randomization and outcome measurement have occurred at the group level are rare. Occasionally wider population level outcomes are measured, for example the multifaceted STD/HIV Intervention Project (SHIP) where peer educators delivered individual and group interventions resulting in dramatic and sustained improvements in sexually transmitted infections at a population level [36]. As with cluster randomized trials, individuals in a group cannot be considered to be inde- pendent of each other and variation in the outcome is likely to be smaller for participants treated in the same group than for participants treated in different groups. Similarly, if the same group leader delivers the interven- tion to different groups of participants, the outcome may differ less than the outcome for participants treated by different group leaders. This design clustering is an additional consideration when deciding whether to ran- domise individuals or clusters to a group intervention. What happens within a group? Table 3 proposes a series of questions examining the micro-level of interactions between the group leader,