Mediated effect of cognitive behavioural therapy on depression outcomes

Introduction Understanding how the intervention works is a primary objective in most pragmatic trials. Although good evidence exists for the effectiveness of cognitive behaviour therapy (CBT), there is little evidence presently that cognitive factors, such as dysfunctional attitudes (DAS) or meta-cognitive awareness (MAQ), mediate the effect of CBT on depression outcomes. Standard regression methods adjusting for such mediators produces biased estimates. Using data from the CoBalT trial, we use a ‘causal inference’ approach to examine the mechanism through which CBT affects depression outcomes.