Approaches for synthesising complex mental health interventions in meta-analysis

Clinical and statistical heterogeneity are commonplace in meta-analysis of mental health interventions. One possible source of this heterogeneity is the complexity of the intervention being evaluated. Complexity may relate to the intervention, or to the way in which it is implemented; however, the most common interpretation of a complex intervention is one which has multiple, potentially interacting components. In this article we outline different analytical strategies suggested for incorporating intervention complexity in a meta-analysis.