Creswell (2017) reviews the growing number of randomised controlled trials (RCTs) investigating the effects of mindfulness interventions (MIs).  These provide consistent evidence that, compared to treatment as usual (TAU) and no-treatment, MIs improve the management of chronic pain, reduce depressive relapse in at-risk individuals, and improve substance abuse outcomes.  There is some evidence that MIs are more effective than behavioural treatments such as relaxation and health education programs (HEPs.)  There is limited evidence for MI efficacy over gold-standard pharmacological or behavioural treatments.  The review also considers the institutional use of MIs, underlying psychological and neurobiological mechanisms, dose response relationships and risks of MIs.

Openly attending to one’s present moment experience, is a useful working definition of the mindfulness component in a range of MIs which have been studied using RCTs.  Group-based MIs are often 8-weeks long.  These include mindfulness-based stress reduction (MBSR) for treating chronic pain and stress, mindfulness based cognitive therapy (MBCT) for treating depressive relapse and mindfulness based relapse prevention (MBRP) for treating addictions.  Retreats and brief interventions are MIs with a range of intensities, from residential retreats, through brief interventions (2-3 weeks, or a few days), down to single-session experimental inductions.  Internet and smartphone apps are an increasingly common means of delivering MIs to large or hard to reach populations.  Control treatments used to test MI efficacy have included treatment as usual (TAU), wait-lists, an 8-week health enhancement programs (HEP), relaxation, and placebo, including sham mindfulness.

RCTs have demonstrated that MIs can have positive effects on both physical and mental health.  There is compelling evidence that MIs reduce chronic pain (e.g. lower back pain, arthritis) relative to TAU, and some evidence that they are more effective than active controls such as HEP.  There is early evidence that MIs boost immunity and have positive effects on stress-related conditions such as fibromyalgia, IBS, breast cancer and psoriasis, but less is known about the effects of MIs on behaviours such as smoking, unhealthy diets and sleep.  One interpretation of these findings is that MIs improve physical health by reducing stress and increasing resilience.  In terms of mental health, there is strong evidence that MIs can reduce depressive relapse and substance abuse relapse.  MIs can also reduce symptoms of anxiety and post traumatic stress disorder.  In healthy young adults, MIs have been shown to improve sustained attention and working memory, and to reduce rumination.  Limited numbers of RCTs studying interpersonal outcomes show that MIs may improve relationship satisfaction and prosocial behaviours.  More research is needed into the effects of MIs across developmental groups including children, pregnant women and older adults, and into the effects of embedding mindfulness into institutions including schools, workplaces and prisons.

RCTs are also contributing to an understanding of the psychological and neurobiological mechanisms underlying MIs.  The clearest psychological factor underlying the effects of MIs is an increasingly decentered or meta-cognitive relationship towards moment-to-moment experience.  More research is needed to evaluate alternative psychological mechanisms including acceptance, emotion regulation, exposure, reduced rumination, self-concept and behavioural mechanisms.  Evidence supporting neurobiological mechanisms underlying MIs more is limited.  However there is structural evidence that MIs increase hippocampal grey matter, and functional differences underlie accounts by which MIs can act as a stress buffer, improve emotion regulation and reduce subjective pain.

More research is needed to establish precise dose-response relationships and risks associated with MIs.  There is evidence that even very brief MIs produce effects, although effect sizes increase with longer interventions such as MBSR.  Negative reactions to MIs such as agitation, anxiety, or discomfort, are not uncommon but under the right supervision can be therapeutically desirable.  These reactions increase with MI intensity, and participants with existing conditions such as past trauma, or high stress are more at risk of extreme negative reactions.  There is some evidence that MIs can be cognitively depleting.

References

Creswell, J. D. (2017). Mindfulness Interventions. Annual Review of Psychology, 68(1), 491–516.

Link to Original:   https://doi.org/10.1146/annurev-psych-042716-051139