Background Mindfulness-based interventions are increasingly being implemented worldwide for problems with depression and anxiety, and they have shown evidence of efficacy. However, few studies have examined the effects of a mindfulness-based group therapy based on standard programs for depression and anxiety until follow-up in Japan. This study addresses that gap. Furthermore, this study explored the mechanisms of action, focusing on mindfulness, mind wandering, self-compassion, and the behavioral inhibition and behavioral activation systems (BIS/BAS) as possible mediators. Methods We examined 16 people who suffered from depression and/or anxiety in an 8-week mindfulness group therapy. Measurements were conducted using questionnaires on depression and trait-anxiety (outcome variables), mindfulness, mind wandering, self-compassion, and the BIS/BAS (process variables) at pre- and post-intervention and 2-month follow-up. Changes in the outcome and process variables were tested, and the correlations among the changes in those variables were explored. Results Depression and anxiety decreased significantly, with moderate to large effect sizes, from pre- to post-intervention and follow-up. In process variables, the observing and nonreactivity facets of mindfulness significantly increased from pre- to post-intervention and follow-up. The nonjudging facet of mindfulness and self-compassion significantly increased from pre-intervention to follow-up. Other facets of mindfulness, mind wandering, and the BIS/BAS did not significantly change. Improvements in some facets of mindfulness and self-compassion and reductions in BIS were significantly correlated with decreases in depression and anxiety. Conclusions An 8-week mindfulness group therapy program may be effective for people suffering from depression and anxiety in Japan. Mindfulness and self-compassion may be important mediators of the effects of the mindfulness group therapy. Future studies should confirm these findings by using a control group. Trial registration University Hospital Medical Information Network (UMIN CTR) UMIN000022966. Registered July 1, 2016, https://upload.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000026425

The mechanisms of efficacy in mindfulness-based interventions for depression and anxiety are not fully understood. To clarify these mechanisms, we tested the hypotheses that mind-wandering, daydreaming, cognitive fusion, and experiential avoidance will decrease through mindfulness group therapy, and this decrease will correlate with improvements in depression and anxiety. Participants self-reported depression and/or anxiety (N = 28) took part in an 8-week mindfulness group therapy program. They were assessed using self-report scales at pre- and post-intervention, and at 2-month follow-up. Results indicated that depression and trait-anxiety decreased between pre- and post-intervention with moderate effect sizes, which were maintained at follow-up. Mind-wandering and cognitive fusion also decreased between pre- and post-intervention with small to moderate effect sizes, and maintained at follow-up. The decreases in mind-wandering and cognitive fusion moderately correlated with improvements in depression and anxiety, suggesting that decreases in mind-wandering and cognitive fusion might underlie efficacious mechanisms of mindfulness group therapy.

Self-compassion is regarded as a mediating or moderating variable in mindfulness-based interventions (MBI). However, few studies have investigated the role of self-compassion on MBI. Therefore, we conducted a randomized controlled trial to examine whether (1) MBI decreases depression and trait anxiety, while increasing trait mindfulness, trait self-compassion, self-compassionate behaviors (SC behaviors), and behaviors, along with improving mood; and (2) SC behaviors moderate the effect of mindful behaviors on mood in daily life. Participants were patients with depression and/or anxiety ( N=19) in Japan. Of the 27 participants recruited, 19 participated in the study. Using stratified randomization, we allocated 10 participants to the intervention group, with an 8-week standard MBI, and nine to the waitlist control group. Depression, trait anxiety, trait mindfulness, and trait self-compassion were assessed using questionnaires, while SC behaviors, mindful behaviors, and mood were measured using an ecological momentary assessment—a method used to repeatedly record events and behaviors in daily life. The results revealed that depression, trait anxiety, trait mindfulness, and trait self-compassion did not significantly change. However, SC behaviors, mindful behaviors, and mood significantly improved with MBI. Moreover, the interaction between SC behaviors and mindful behaviors was significantly shown in the pre-intervention, suggesting that SC behaviors moderate the effect of mindful behaviors on mood in daily life.

We thank Prof. Rieko Osu, Waseda University, for her revision of the manuscript.Additionally, we are grateful to Masahiro Fujino, Ph.D., Kyoto University for helping with recruitment of participants. We would like to thank Editage (www.editage.jp) for English language editing. This work was supported by

Mindfulness meditation might improve the flexibility of mind-wandering, that is, the ability to shift attention from mind-wandering. Flexibility of mind-wandering could mediate the relationship between mindfulness and improvement in depression. However, there have been no studies of this relationship because of limitations in measurement methodology. Since the mindfulness-based intervention, which instructs participants to be aware of the occurrence of, and their own engagement in, mind-wandering, might bias self-reports of mind wandering, a measurement method that does not rely on participants’ verbal report is needed. Therefore, we propose a novel method to evaluate the flexibility of mind-wandering, based on mind-wandering intensity estimation by machine-learning using electroencephalography. We estimated mind-wandering intensity using one-second electroencephalogram samples and a machine-learning model developed in previous research. Thus, we observed fluctuations in mind-wandering during a 14-minute meditation and defined the time required to shift attention from mind-wandering as an index of mind-wandering flexibility. We performed two experiments: The first targeted experienced meditators and the second assessed non-meditators before and after participating in a mindfulness-based intervention. These experiments revealed that flexibility of mind-wandering was correlated with the extent of meditation experience. In addition, the magnitude of the decrease in flexibility and severity of depression following the intervention were found to be correlated.