Mixed treatment comparison meta-analysis of complex interventions: psychological interventions in coronary heart disease.

Meta-analyses of psychological interventions typically find a pooled effect of "psychological intervention" compared with usual care. This answers the research question, "Are psychological interventions in general effective?" In fact, psychological interventions are usually complex with several different components. The authors propose that mixed treatment comparison meta-analysis methods may be a valuable tool when exploring the efficacy of interventions with different components and combinations of components, as this allows one to answer the research question, "Are interventions with a particular component (or combination of components) effective?" The authors illustrate the methods using a meta-analysis of psychological interventions for patients with coronary heart disease for a variety of outcomes. The authors carried out systematic literature searches to update an earlier Cochrane review and classified components of interventions into 6 types: usual care, educational, behavioral, cognitive, relaxation, and support. Most interventions were a combination of these components. There was some evidence that psychological interventions were effective in reducing total cholesterol and standardized mean anxiety scores, that interventions with behavioral components were effective in reducing the odds of all-cause mortality and nonfatal myocardial infarction, and that interventions with behavioral and/or cognitive components were associated with reduced standardized mean depression scores.