Authors' reply to "Recommendations for conducting mindfulness based cognitive therapy trials".

To the Editors: We appreciated very much the commentary by Siddaway and Wood (2013) on our review and meta-analysis “Mindfulness based cognitive therapy for psychiatric disorders: A systematic review and meta-analysis” (Chiesa and Serretti, 2011) and we are grateful for having the possibility to further explore the issues they raised. As the authors of the commentary noted, the main findings of our meta-analysis were that mindfulness-based cognitive therapy (MBCT) as an adjunct to treatment as usual (TAU) could be significantly superior to TAU only and the combination of MBCT and gradual discontinuation of antidepressant therapy could be as efficacious as the continuation of maintenance antidepressant therapy for the prevention of depressive relapses in recovered depressed patients with three or more prior depressive episodes (Chiesa and Serretti, 2011). In addition, we also found that MBCT+TAU could be significantly superior to TAU only for the reduction of residual depressive symptoms in currently depressed patients (Chiesa and Serretti, 2011). However, the authors of the commentary also noted that our critique of the methodology employed in MBCT trials to date did not go far enough and they cautioned against the assumption that “third wave” cognitive therapies, such as MBCT, are unequivocally superior to first or second wave therapies. The present response is aimed at further exploring our conclusions in relationship to the issues raised by the authors of the commentary. First of all, we would like to underscore that in the discussion of our work we did not suggest that “third wave” cognitive therapies, such as MBCT, are unequivocally superior to first or second wave therapies. Rather, we underscored that, taking into account the inadequate sophistication of the control groups, further better designed studies should be aimed at distinguishing between the specific and the non-specific effects of MBCT. Results in this direction can usually be achieved through different study designs. A first possibility is to employ a control group that is specifically structured to include the majority of non-specific “ingredients” of the active treatment under investigation, including, among others, benefits' expectation, teacher's care, group support, contact time with the therapist and amount of home practice, while excluding the claimed active ingredient (or ingredients) of the treatment under investigation, such as mindfulness meditation practice (Chiesa, 2011). If MBCT is found to be superior to such control condition, it can reasonably be suggested that MBCT could provide patients with significantly higher benefits than those expected only in relationship to the non-specific elements of MBCT. It is worth mentioning that, since the publication of our review and meta-analysis, some preliminary results in this direction have been published. As an example, the preliminary results of an ongoing trial from our group suggested that MBCT could be more efficacious than a psycho-educational group designed ad hoc to match as much as possible the non-specific elements of MBCT for the reduction of depressive symptoms in depressed patients with residual depressive symptoms (Chiesa et al., 2012). A second possibility to rule out that the effects of a new treatment, such as MBCT, are only due to non-specific elements is to compare such treatment with an existing treatment that already proved efficacy for the specific condition under investigation (for better details see Chiesa (2011)). Although limited by the small sample size and the lack of an a priori power calculation, the results of a recent randomized controlled trial provided preliminary evidence to suggest that MBCT could be as efficacious as group cognitive behavioural therapy (CBT) to reduce depressive symptoms in currently depressed patients (Manicavasgar et al., 2011). In addition, in a further randomized controlled trial, Segal et al. (2010) found that MBCT+gradual discontinuation of antidepressant therapy could be as efficacious as the continuation of maintenance antidepressant therapy and that both treatments could be more efficacious than placebo for the prevention of depressive relapses in recovered patients with major depression. In sum, the results of some recent randomized controlled trials aimed at exploring the efficacy of MBCT for the prevention of major depression relapses and for the reduction of acute and residual depressive symptoms provided preliminary support for the notion that MBCT could be associated with specific effects in addition to the non-specific effects that are shared by all psychological and pharmacological treatments. However, the results of these studies do not (or do not yet) provide support to the notion that MBCT is superior to other first or second wave cognitive treatments and do not unequivocally provide information about the distinctive features of MBCT. To the best of our knowledge, no trial has yet been published that specifically provided support to the notion that MBCT is superior to established treatments for the treatment of psychological disorders such as major depression. In addition, as the authors of the commentary aptly noted, we agree that, as the investigation of MBCT moves forwards, it will be increasingly important to compare MBCT with different active control conditions that are aimed at testing each specific ingredient of the MBCT program, including, among others, the underlying interactive cognitive system (ICS) theoretical model, the particular contribution of changing the content of cognitions versus changing the function and process of cognitions and the contribution of low arousal affective states. In line with these issues, an important question raised by the authors of the commentary to our review and meta-analysis is whether the ICS information-processing theory that underpins MBCT and purports to specifically explain recurrent episodes of depression (Teasdale et al., 1995) can be adapted to treat a range of acute problems. We also agree with the authors that, because several recent trials investigated the efficacy of MBCT as a treatment for a range of acute problems and sometimes tweaked the MBCT protocol, they could be re-interpreted as dismantling studies that provide important evidence regarding shared and unique therapeutic factors. Similarly, we agree with the authors of the commentary that further challenging issues, including the reasons behind the notion that MBCT could help prevent relapses in patients with three or more previous depressive episodes but not in those with only two previous depressive episodes and the need for investigating the neural mechanisms of MBCT, require further investigation so as to better understand the mechanisms underlying MBCT as well as its strengths and limitations as a means to treat a different set of clinical conditions. In conclusion, we underscore that available studies provide preliminary support to the efficacy of MBCT for the prevention of depression relapses and the reduction of depressive symptoms in patients suffering from major depression. However, future trials investigating the original and the many adapted versions of MBCT should employ stronger methodological paradigms aimed at (1) distinguishing between the specific and the non-specific effects of MBCT, (2) investigating the distinctive features of MBCT in comparison with several related interventions such as Mindfulness based Stress Reduction, CBT or relaxation training, (3) understanding to which extent the ICS model that underpins MBCT can be adapted to treat a range of different acute problems, (4) investigating the psychological and neurobiological mechanisms of action of MBCT and (5) providing evidence as to which adaptations are needed so as to best tailor future MBCT programs and studies to the unique needs, learning styles and temperamental profiles of individuals suffering from different clinical conditions in different phases of their disorder.