Cognitive mechanisms of MBCT on depressed older adults : the mediating role of rumination and autobiographical memory specificity

Abstract

Rumination and reduced autobiographical memory specificity (AMS) are dysfunctional cognitions commonly found amongst individuals with depression. They are independently associated with a series of detrimental consequences, and together they form a dysfunctional process that reinforces each other in a spiral interaction. This can be particularly problematic in late adulthood because of age-dependent changes that convolute the presentation and inter-relationships of these dysfunctional cognitions with depression. In the search for an effective transdiagnostic intervention for depressed older adults, the theoretical underpinnings of mindfulness-based cognitive therapy (MBCT) appear to address the underlying mechanisms of ruminative tendencies and non-specific memory retrieval. However, empirical support for the efficacy of MBCT in depressed older adults is limited and little is known about how MBCT might work for this specific population.

To better understand the characteristics of dysfunctional cognitions in late adulthood and means to alleviate them, this study has three major objectives: 1) to generate a cross-sectional profile on the presentation of dysfunctional cognitions in older adults, 2) to examine the effectiveness of MBCT in older adults in a randomised controlled trial and 3) to explore the mechanisms by which MBCT alleviates depressive symptoms in older adults.

The cross-sectional profile consisted of 84 participants. All participants completed assessments on depressive symptoms, AMS, rumination, trait mindfulness and cognitive ability. Among them, 57 participants with mild to moderate depressive symptoms were invited to participate in the randomised controlled trial. They were allocated to either the MBCT group or the low-intensity exercise active control group. The participants who attended at least 80% of the sessions underwent re-assessment after the 8-week intervention.

The cross-sectional profile of older adults indicated a strong and positive association between rumination and depression severity, but there was only a small predictive relationship between AMS and depression. The findings of the randomised controlled trial revealed a significant reduction in depressive symptoms in both the MBCT and active control group, but only participants in the MBCT group showed substantial improvements in AMS, rumination and trait mindfulness level. Bootstrapping-based mediation analyses show that the effects of MBCT in alleviating depressive symptoms were only mediated by a reduction in rumination.

In conclusion, rumination remained as a prominent dysfunctional cognition in older adults with depression whilst AMS was increasingly susceptible to age-dependent changes. The promising findings from the randomised controlled trial implicate that MBCT is an effective intervention for older adults with active depressive symptoms, and learning how to disengage from ruminative thoughts played a major role in the cognitive mechanism of MBCT. Current findings extend the growing evidence for the efficacy of MBCT to older adults, and the generation of a cross-sectional profile also elucidates the convoluted inter-relationships of these dysfunctional cognitions in late adulthood. Together they illuminate the specific therapeutic components of MBCT and its applicability for older adults with depression.