A distinctive and almost unique feature of cognitive behavioural therapies (CBT) is their claim to be based on specific psychological theories, which relate the origins and maintenance of a psychological disorder to specific interventions. The resulting therapeutic impact of such interventions is thus mediated by some theoretically-relevant change mechanism. Indeed, the ultimate test of the efficacy and veracity of such an intervention is whether or not significant therapeutic change is directly linked to process measures of underlying theoretically-relevant mechanisms. These are very exacting and challenging criteria that few, if any, psychological therapies have yet to achieve.

Although many trials of CBT clearly demonstrate efficacy and therapeutic gain compared to control, placebo or other interventions, only a few interventions also demonstrate predicted, theoretically-relevant changes in process measures of change. It is also the case that many highly proficient CBT therapists might be hard pressed to elaborate in detail the underlying psychological theories and empirical evidence upon which their interventions are based. Hence, the book by Kazantzis and colleagues promises to reveal what these therapeutic theoretically-based mechanisms might be and how they relate to clinical practice. It ought to illuminate theories and provide the underpinnings of clinical practice. Does it achieve such ambitious goals?

The first chapter by Emmelkamp, Ehring and Powers rises to the challenge of the relationship between theory and therapy; they review the theoretical underpinnings of CBT focusing on learning theories, cognitive theories and so-called “third generation therapies”. They contrast the importance of theory for the development of early learning-theory based interventions, with the rise of evidence-based therapies and empirically supported treatment, whereby the proof of efficacy was derived from randomized control trials. They contrast this to theory-based individualized or formulation-based approaches and attempt to review the evidence of process-orientated trials that support both efficacy and theoretically-linked process changes. They conclude that with the possible exception of panic disorder, the evidence of a strong integration between evidence-based and theoretical interventions is slight.

The rest of the book consists of overviews of various different CBT interventions. Indeed, the range of interventions and the diversity of theoretical underpinnings belies the notion of a unified CBT intervention. Generally, each chapter is structured around a review of the philosophical and theoretical underpinnings of a particular therapeutic approach, the empirical support or evidence and some practical illustrations using clinical material. The chapters include: Beck's Cognitive Therapy (Scott and Freeman), Problem Solving Therapy (Nezu, Nezu and D'Zurilla), Rational-Emotive Therapy (DiGiuseppe), Acceptance and Commitment Therapy (Waltz and Hayes), Behavioural Activation (Martell, Dimidjian and Lewinsohn), Dialectical Behaviour Therapy (Lynch and Cuper), Cognitive Analytic Therapy (Ryle), Positive Psychology and Therapy (Park, Peterson and Brunwasser), Mindfulness-based Cognitive Therapy (Dimidjian, Kleiber and Segal), and Emotion-focused/Interpersonal Cognitive Therapy (Safran, Eubanks-Carter and Muran). The success to which the theoretical foundations of particular approaches are revealed and supported by the evidence varies considerably across the different contributions. Nevertheless, the book provides an excellent overview of CBT interventions and demonstrates that CBT is a rich and wide-ranging set of therapeutic interventions. Moreover, it provides for the clinician a practical and clinical context with which the theoretical and therapeutic potentially come together.

My only reservation is that there were not more general chapters such as the introductory one dealing with the relationship between theory and practice. An obvious area would be to look at individual psychological formulations versus diagnostic approaches to treatment. Similarly, a review of transdiagnostic approaches to the treatment of sleep disorders, memory dysfunction, attentional dysfunction, rumination and worry would have also provided a counterpoise to merely reviewing theoretical underpinnings of particular approaches.