The aim of this study was to conduct a preliminary randomized controlled trial to investigate whether MBCT can successfully reduce symptoms of depression in currently symptomatic patients who suffer from a protracted course of the disorder and in whom spontaneous recovery is relatively unlikely to occur. Previous RCTs had excluded such patients on the grounds that MBCT might be inappropriate unless patients were in remission or recovery; though there had been promising results from uncontrolled trials (Eisendrath et al., 2008
; Finucane & Mercer, 2006
; Kenny & Williams, 2007
). Consistent with these studies, our results showed that treatment with MBCT significantly reduced self-reported symptoms of depression from severe to mild levels, while levels of depression remained unchanged in the group that received TAU only. Numbers of patients who met criteria for Major Depression decreased in the MBCT group but remained in the TAU group.
While the current study extends previous research by using a randomized controlled design and blind assessments, there are a number of limitations that need to be taken into account. First of all, and most importantly, this study is based on only a small sample of patients. Because of this, the study is potentially more vulnerable to spurious effects and generalizability of its findings is more uncertain. One potential difficulty that comes with small numbers is that randomization is more likely to fail to produce groups that are comparable in all important respects. The two groups here differed with regard to the proportion of participants classified as currently being in a full chronic episode of depression as compared to suffering from residual symptoms following a full episode. Because of this imbalance, it could be argued that part of the differential changes in symptoms found may be due to participants in the TAU group being less likely to show spontaneous recovery because of the more chronic nature of their depression. While this possibility cannot be completely ruled out, there are several points that speak against it. First, when length of current episode was used as a covariate in analyses of BDI-II changes, results remained significant. Second, previous research on chronic depression has demonstrated that, while diagnostic systems differentiate between chronic episodes of depression and recurrent depression without full inter-episode remission, these two forms share more similarities than there are differences between them in terms of clinical features and risk factors (McCullough et al., 2003
). Consistent with this, the two groups in our study, although different in terms of numbers of those suffering from chronic episodes, did not differ in total length of time they had suffered from depression in their lifetime nor length of the last episode when ongoing residual symptoms were taken as part of the episode.
A second important limitation of the study is that the main findings regarding severity of depressive symptoms are based on self-reports, which are amenable to subjective biases. Ideally, these measures would have been complemented by observer-rated measures of symptom severity. However, while there was no such measure for symptom severity, the study did include structured interviews to assess diagnostic status before and after the treatment phase. Although comparisons of numbers of participants who qualified for a full diagnosis of depression were restricted because some of the participants did not meet full criteria for a diagnosis of Major Depression at pre-assessment, analyses yielded significant effects indicating stronger decreases in number of patients meeting full criteria in the MBCT group (70% no longer meeting diagnostic criteria) than in the TAU group (18%).
The current sample was characterized by a protracted course of the disorder and all of the participants had suffered from suicidal ideation in the past. Both established psychotherapeutic and pharmacological treatments have been found to fail to help a significant number of these patients. For example, in a large recent study of cognitive therapy for severe depression, where many of the patients included reported a recurrent or chronic course of the disorder, rates of response were 58% (DeRubeis et al., 2005
). A large study investigating a treatment specifically designed for chronic depression, the Cognitive Behavioral-Analysis System of Psychotherapy (CBASP), found satisfactory responses after 16–20 sessions of individual therapy in 48% of patients, a rate that increased to 73% in those who received both CBASP treatment in addition to psychopharmacological treatment with the antidepressant nefazodone (Keller et al., 2000
). Given the relatively low intensity of MBCT with only eight weekly sessions and the economic advantage of the treatment being delivered in groups, the rates of response found in our study can be judged as generally encouraging. Direct comparisons of rates of response between this and other studies need to take into account that the current study used a combined criterion requiring both severity levels below a certain threshold level and percentage change as compared to use of a threshold level only.
Despite the fact that, initially, the developers of MBCT had cautioned against its use in currently depressed patients, rates of attendance at classes and the data from participants' records of homework practice suggest that the treatment is both acceptable and manageable for this group. These data were in line with the clinical impressions from the classes. Because of their current symptoms, we had expected that patients would encounter more negative content during their meditations and one particular concern had been that, especially in the early stages of the treatment, participants might get easily overwhelmed by this negative content and find it more difficult to use the meditation techniques to their advantage. In cases where this seemed to be a problem, we offered participants the opportunity to choose their home practice more flexibly, and, when needed, to use practices that provided particularly tangible anchors for their attention such as sensations of the body during yoga stretches or the sensations of the breath during sitting meditations. Another variation offered to participants was to experiment, in sitting meditations, with opening their eyes at times when they found content to be overwhelming and to use this technique to approach difficult content in a stepwise manner. Clinical impressions suggested that only a small number of patients required and made use of these variations of the standard practice.
While results showed significant decreases in severity of depressive symptoms, we did not find significant changes in suicidal ideation. In part, this may be due to lack of power for detecting such differences as a large number of patients entered the study with relatively low levels of suicidal ideation. Taken as they are, though, these findings suggest the need to address suicidal thinking in even more detail. Possible additions could, for example, include a psychoeductional component on the impact of suicidal imagery and the immediacy with which such imagery can occur and impact. Recent research has suggested that suicidal patients, when at their most despairing, often suffer from intrusive mental images of suicide and that the frequency and subjective reality of such images is significantly related to severity of suicidal ideation (Holmes, Crane, Fennell, & Williams, 2007
). Yet, available treatments so far have not included a specific focus on this aspect of psychopathology.
Research on the effects of meditation has been growing over the recent years and studies suggest that regular meditation practice can produce lasting effects on attention, executive functioning (Lutz, Slagter, Dunne, & Davidson, 2008; Slagter et al., 2007; Tang et al., 2007
) and emotion regulation (Nielsen & Kaszniak, 2006
). Systematic training of these functions through meditation may be particularly helpful in patients suffering from chronic depression where vulnerability processes such as rumination are likely to have acquired a habitual and automatic character and are more likely to occur when cognitive control is undermined. This small-scale randomized controlled trial comparing MBCT to TAU represents a logical next step in testing the application of MBCT in chronic depression, following positive reports from clinical audits. Altogether, the findings provide preliminary evidence suggesting that using mindfulness meditation in the treatment of chronic or recurrent depression is feasible and may provide a valuable addition to already established interventions. Further research into the effects of mindfulness meditation will help to tailor the MBCT program more specifically to the needs of this group. The focus here was on immediate effects and future studies need not only replicate the current findings but should also use more extensive follow-ups given the high risk of relapse in the histories of these patients as well as active treatment comparisons in order to control for unspecific effects of the MBCT training.