Establishing how psychological therapies work: the importance of mediation analysis.

This editorial reviews the literature regarding psychological studies that are designed to address the question of not just whether, psychological interventions effect change, but how. The practicalities and implications of assessing mechanisms of treatments are considered with examples from the fields of Cognitive Behavioural Therapy (CBT) and Mindfulness. The potential for elucidating theoretical mechanisms, developing new theoretical models and modifying treatment approaches are described. In addition an overview of different types of statistical methods available to researchers for assessing mediation is given. Structural Equation Modelling (SEM) is a recommended approach. The review concludes with a summary of optimum study conditions adopted by researchers for establishing mediating effects.