Mindfulness‐based cognitive therapy and depression relapse—evaluating evidence through a meta‐analytic lens may indicate myopia

Abstract

For those affected by Major Depressive Disorder (MDD) relapse remains a major problem, with 35% of people with a major depressive episode experiencing at least one relapse.1 Interventions to prevent relapse include maintenance antidepressants, as well as a number of psychosocial interventions, amongst them Cognitive Behavioural Therapy (CBT), Interpersonal therapy (IPT), Behavioural Activation and Mindfulness-Based Cognitive Therapy (MBCBT). MBCBT is a relatively recently developed psychotherapy, consisting of manualised group skills training, based on the principles of CBT and mindfulness-based stress reduction. It was developed specifically for relapse prevention in depression and has been investigated in a number of randomised controlled trials (RCTs). It is recommended as a maintenance treatment for depression in a number of guidelines, amongst them the UK National Institute for Health and Care Excellence (NICE),2 Canadian Network for Mood and Anxiety Treatments (CANMAT),3 and Royal Australian and New Zealand Clinical Practice Guidelines (RANZP).4 In this issue of Acta Psychiatrica Scandinavica, McCartney and colleagues present the results of a pairwise and network meta-analysis of mindfulness-based cognitive therapy for prevention of relapse of depression and time to relapse.5 Any attempt at synthesis of the literature in this field is to be welcomed and will likely have important clinical ramifications. By conducting a network meta-analysis, the authors also attempt to bypass the limitations of including only trials involving direct comparisons, thus enabling further comparisons. This approach may therefore add to existing evidence from pairwise and individual patient data meta-analysis. The headline findings appear to give cause for optimism versus treatment-as-usual (TAU) MBCBT shows a statistically significant difference in preventing depression relapse and, compared to TAU and placebo, an increase in time to relapse (though only one trial contributed to the placebo comparison). This is in keeping with findings of an individual patient data meta-analysis, which showed similar results for reates of relapse.6 Therefore, on the face of it, this meta-analysis provides support for guideline recommendations, and possibly the wider use of this intervention. However, meta-analyses (both pairwise and network) are only as strong as studies included and close examination of evidence contributing to this meta-analysis reveals pertinent limitations in trial methodology. Cuijpers and Cristea neatly outline some of these factors7 which include, though are not limited to, allegiance bias, expectancy effects, choice of comparator (active controls versus waiting list), small sample size and selective reporting. Any novel therapy examined by its proponents is at risk of allegiance bias—for some reason or another, effect sizes are higher in trials conducted by those who have an interest in the novel technique and may have more expertise in delivering the intervention. Examining studies included here, a number of larger trials were performed by original proponents of MBCBT. These trials were generally positive and contributed significantly to the overall results of the meta-analysis. It should be acknowledged that at the time of the original Teasdale trial (in 2000), there was little evidence for psychotherapies in preventing depression, and therefore, this was a novel trial. Nonetheless, readers should be aware that aspects of methodology were not as stringent as one would expect in trials today (eg initial stratification of the sample for randomisation by 2 or more episodes of depression, intention to treat analysis of people with three or more episodes, as opposed to people with two or more episodes,8 Non-significant findings for people with 2 or more episodes may have been the result of decreased statistical power, though this is unclear.9) The follow-up study with Teasdale as main author10 demonstrated a significant difference for people with three or more episodes, though not for two prior episodes. The treatment-as-usual group experienced a 100% relapse rate. In terms of comparators, it should come as little surprise that in the meta-analysis, this intervention showed a benefit compared to TAU, though not in comparison to other active interventions such as minimal antidepressant medication, an active control condition, cognitive psychological education,