Objectives
Change factors common across psychosocial interventions, including those relating to group treatments, are often not addressed within research into mindfulness-based programmes (MBPs). Here, we present how consideration of these factors can be beneficial for both mindfulness teachers and researchers.

Methods
This article is a selective review of relevant common factors and small group treatment research and practitioner literature. This encompasses emergent and imposed structure, formal change theory, foundational social processes and emergent process, as well as teacher and client effects. Extant qualitative and quantitative research and key practitioner literature into MBPs is included, and implications for mindfulness teachers both from the wider framework of common and group factors, as well as from MBP research itself, are outlined.

Results
Participant expectations and preferences may play a role in supporting good outcomes and course continuation in MBPs, but more research is needed. Participants and practitioners describe the importance of the group crucible, including the experience of common humanity and connection, and group composition may impact this. Group size is under-researched and it is unclear what influence this may have on effectiveness. Surprisingly, research thus far has not found a reliable link between participant outcome and teacher competence, though embodiment is considered key by practitioners, trainers and participants.

Conclusions
Future research should focus on the role of expectations, alliance, the group context and group size as well as finding innovative ways to further understand MBP teacher competence.