Defining and Measuring Mechanisms of Change in Psychological Therapies: The Path Not Taken

Metcalf and Dimidjian (this issue) have provided an important review of the current evidence base for mindfulness‐based cognitive therapy (MBCT) and presented a helpful summary of the proposed mechanisms of change. It is necessary to engage in a continuous dialogue regarding the evidence base for change mechanisms, and the article by Metcalf and Dimidjian highlights an important barrier of concern to the field of treatment outcome research. The present commentary aims to expand the discussion regarding the definition, measurement, and evaluation of “mechanisms of change.” Using MBCT as an example, this commentary addresses the ambiguity surrounding the definition and operationalisation of these mechanisms in research on psychological therapies and how the method of measurement may impact the results obtained in clinical trials. It is argued that a potentially fruitful avenue of future research would involve investigation of techniques, important client‐therapeutic processes, and mechanisms in a single study in order to comprehensively evaluate how change occurs.