How does MBCT for depression work? studying cognitive and affective mediation pathways

Abstract

Mindfulness based cognitive therapy (MBCT) is a non-pharmacological intervention to reduce current symptoms and to prevent recurrence of major depressive disorder. At present, it is not well understood which underlying mechanisms during MBCT are associated with its efficacy. The current study (n = 130) was designed to examine the roles of mindfulness skills, rumination, worry and affect, and the interplay between those factors, in the mechanisms of change in MBCT for residual depressive symptoms. An exploratory but systematic approach was chosen using Sobel-Goodman mediation analyses to identify mediators on the pathway from MBCT to reduction in depressive symptoms. We replicated earlier findings that therapeutic effects of MBCT are mediated by changes in mindfulness skills and worry. Second, results showed that changes in momentary positive and negative affect significantly mediated the efficacy of MBCT, and also mediated the effect of worry on depressive symptoms. Third, within the group of patients with a prior history of ≤ 2 episodes of MDD, predominantly changes in cognitive and to a lesser extent affective processes mediated the effect of MBCT. However, within the group of patients with a prior history of ≥ 3 episodes of MDD, only changes in affect were significant mediators for the effect of MBCT.

Trial registration: [corrected] Nederlands Trial Register NTR1084.

Figure 1. CONSORT participant flow diagram.

MBCT = Mindfulness-based Cognitive Behavioral Therapy; CONTROL = waitlist control condition.

Figure 2. Mediation analysis pathway, for the effect of MBCT on residual symptoms of depression.

N.B. All variables are change scores over time. The numbers show the four different levels of analyses.

Figure 3. Graphical display of the resulting significant mediations for the total group and the two subgroups (≤2 MDE & ≥3MDE).

A Mediating mechanisms MBCT for total group. B Mediating mechanisms MBCT for subgroup two or less depressions. C Mediating mechanisms MBCT for subgroup three or more depressions. The numbers in the figure show the percentage of mediation (indirect effect) of that mediator on the next phenotype. The figure can be conceived as consisting of mediation-triangles, where on top of the triangle the percentage of mediation is shown. For example in Figure 2a, the effect of MBCT on IDS-SR³⁰ is mediated for 51% by PSWQ (and the effect of PSWQ on IDS-SR³⁰, is again mediated by PA & NA). Also, the effect of MBCT on PSWQ is for 48% mediated by KIMS. The reported mediations do not account for a unique effect, but overlap with each other, reflecting a series of separate regressions (one for each triangle).