Mindfulness Practice, Rumination and Clinical Outcome in Mindfulness-Based Treatment

The MBSR group was recruited from one arm of a larger neuroimaging study comparing MBSR against a Progressive Muscle Relaxation active control group. Participants were right-handed adults recruited from a community based sample. Twenty-four participants fully remitted from unipolar depression were randomized into the two active-treatment groups, including the 14 MBSR group participants. Clinical history and remitted status were confirmed through assessment with an experienced clinical psychologist. All remitted patients had a history of one more past episodes of depression at the time of recruitment, with varied levels of ongoing antidepressant medication and psychotherapy. No participants had prior exposure to formal meditation or relaxation training, with the exception of some yoga classes in the past. MBSR participants attended an MBSR course led by experienced MBSR facilitators at the Centre for Addiction and Mental Health.

In the MBCT condition, participants were excluded if they had a current diagnosis of Bipolar Disorder, Substance Abuse Disorder, Schizophrenia or Borderline Personality Disorder or a trial of ECT within the past 6 months, or currently practiced meditation more than once per week or yoga more than twice per week. A full description of inclusion and exclusion criteria, treatment fidelity, and study details can be found in Segal et al. (2010). In the MBSR condition, participants were excluded if they had a current diagnosis of Bipolar Disorder, Substance Abuse Disorder, Schizophrenia, Borderline Personality Disorder, Post Traumatic Stress Disorder, or any Eating Disorder. Further, they were excluded if they had any current meditation practice or if they engaged in yoga. Given that participants completed fMRI scans, they were excluded if they carried a surgically implanted metal device such as a pacemaker.

In order to demonstrate mediation, the RSQ subscales must be measured during treatment, be significantly altered by treatment, and must temporally precede the outcome—although two time points are used, this is the case with the current data since the RSQ is measured on treatment session eight while the HRSD is measured 2 weeks following session eight. Further, the mediator must also then show a main and/or interactive effect with treatment on outcome; (i.e., the mediator and/or interaction term in the regression should be significant) while treatment need not have a significant overall or main effect on outcome. A main effect of mediation is demonstrated when treatment significantly changes the mediator but the effect of the mediator on outcome does not significantly differ across treatment types. In contrast, an interactive mediation effect occurs when treatment not only significantly impacts on the mediator but also changes the relationship between the mediator and outcome such that it differs across treatments. In the current analysis, both the HRSD and the RSQ are measured at two time points; however, the T2 HRSD was typically administered at least 2 weeks after the T2 RSQ, so the T2 RSQ temporally precedes the T2 HRSD administration.

When examining each group separately, path a was significant for both groups; the frequency of formal mindfulness practice predicted changes in rumination although the coefficients differed (MBCT a = −.49, MBSR a = −.44). No significant associations were found between frequency of formal, informal, and total mindfulness practice, as related to distraction. Path b, examining the relationship between rumination and depression symptom change when controlling for the independent variable, was significant for both groups, demonstrating that decreased rumination predicted decreased depressive symptoms (MBCT b = .43, MBSR b = .38). For path c, depressive symptom change was associated with both the frequency of formal mindfulness practice and total mindfulness practice for both groups (MBCT c = −.53; MBSR c = −.49). Finally, for path c’, the relationship between depressive symptom change and formal mindfulness practice remained significant for both groups (MBCT c’ = −.70; MBSR c’ = −.65).