'Third wave' cognitive and behavioural therapies versus treatment as usual for depression.

So-called 'third wave' cognitive and behavioural therapies represent a new generation of psychological therapies that are increasingly being used in the treatment of psychological problems. However, the effectiveness and acceptability of third-wave cognitive and behavioural therapy (CBT) approaches as treatment for acute depression remain unclear. 1. To examine the effects of all third wave CBT approaches compared with treatment as usual/waiting list/attention placebo/psychological placebo control conditions for acute depression.2. To examine the effects of different third wave CBT approaches (ACT, compassionate mind training, functional analytic psychotherapy, dialectical behaviour therapy, MBCT, extended behavioural activation and metacognitive therapy) compared with treatment as usual/waiting list/attention placebo/psychological placebo control conditions for acute depression.3. To examine the effects of all third wave CBT approaches compared with different types of comparators (treatment as usual, no treatment, waiting list, attention placebo, psychological placebo) for acute depression. We searched the Cochrane Depression Anxiety and Neurosis Group Trials Specialised Register (CCDANCTR to 01/01/12), which includes relevant randomised controlled trials from The Cochrane Library (all years), EMBASE, (1974-), MEDLINE (1950-) and PsycINFO (1967-). We also searched CINAHL (May 2010) and PSYNDEX (June 2010) and reference lists of the included studies and relevant reviews for additional published and unpublished studies. An updated search of CCDANCTR restricted to search terms relevant to third wave CBT therapies was conducted in March 2013 (CCDANCTR to 01/02/13). Randomised controlled trials that compared third wave CBT therapies with control conditions for acute depression in adults. Two review authors independently identified studies, assessed trial quality and extracted data. Study authors were contacted for additional information when required. We rated the quality of evidence using GRADE methods. Four small studies (224 participants) were included in the review. Little information was provided about the process of allocating participants to groups. None of the studies used independent outcome assessors, and evidence suggested researcher allegiance towards the active treatments. The four studies examined a diversity of third wave CBT approaches (extended behavioural activation, acceptance and commitment therapy and competitive memory training) and control conditions. None of the studies conducted follow-up assessments. The results showed a significant difference in clinical response rates in favour of third wave CBT when compared with treatment as usual (TAU) conditions (three studies, 170 participants, risk ratio (RR) 0.51, 95% confidence interval (CI) 0.27 to 0.95; very low quality). No significant difference in treatment acceptability based on dropout rates was found between third wave CBT approaches and TAU (four studies, 224 participants, RR 1.01, 95% CI 0.08 to 12.30; very low quality). Both analyses showed substantial statistical heterogeneity. Very low quality evidence suggests that third wave CBT approaches appear to be more effective than treatment as usual in the treatment of acute depression. The very small number of available studies and the diverse types of interventions and control comparators, together with methodological limitations, limit the ability to draw any conclusions on their effect in the short term or over a longer term. The increasing popularity of third wave CBT approaches in clinical practice underscores the importance of completing further studies of third wave CBT approaches in the treatment of acute depression, on a short- and long-term basis, to provide evidence of their effectiveness to policy-makers, clinicians and users of services.