Mindfulness-based interventions for psychiatric disorders: A systematic review and meta-analysis

Highlights

• We examined the relative efficacy of mindfulness-based interventions on clinical symptoms of psychiatric disorders.

• 142 randomized clinical trials were included (N = 12,005 participants). Control conditions were coded on a five-tier system.

• At post-treatment, mindfulness interventions were equivalent to evidence-based treatments and superior to other comparisons.

• At follow-up, mindfulness interventions were equivalent to minimal and evidence-based treatments and superior to others.

• The most consistent evidence for mindfulness-based interventions was seen for depression, pain, smoking, and addictions.

Abstract

Despite widespread scientific and popular interest in mindfulness-based interventions, questions regarding the empirical status of these treatments remain. We sought to examine the efficacy of mindfulness-based interventions for clinical populations on disorder-specific symptoms. To address the question of relative efficacy, we coded the strength of the comparison group into five categories: no treatment, minimal treatment, non-specific active control, specific active control, and evidence-based treatment. A total of 142 non-overlapping samples and 12,005 participants were included. At post-treatment, mindfulness-based interventions were superior to no treatment (d = 0.55), minimal treatment (d = 0.37), non-specific active controls (d = 0.35), and specific active controls (d = 0.23). Mindfulness conditions did not differ from evidence-based treatments (d = − 0.004). At follow-up, mindfulness-based interventions were superior to no treatment conditions (d = 0.50), non-specific active controls (d = 0.52), and specific active controls (d = 0.29). Mindfulness conditions did not differ from minimal treatment conditions (d = 0.38) and evidence-based treatments (d = 0.09). Effects on specific disorder subgroups showed the most consistent evidence in support of mindfulness for depression, pain conditions, smoking, and addictive disorders. Results support the notion that mindfulness-based interventions hold promise as evidence-based treatments.

Introduction

Mindfulness-based interventions have experienced a marked increase in scientific and popular interest in the past two decades. Recent commentaries have, however, raised questions regarding the evidence base for this family of therapies. Farias, Wikholm, and Delmonte (2016) voiced several concerns, particularly the use of non-active control conditions (i.e., waitlist controls) in randomized clinical trials (RCTs) of mindfulness therapies along with a lack of specificity regarding outcomes that these treatments may or may not impact. Others have questioned the degree to which selective reporting of results may introduce systematic bias into the literature, thereby overstating the efficacy of mindfulness-based interventions (Coronado-Montoya et al., 2016).

One recent meta-analysis estimated the effects of meditation-based interventions (including mindfulness as well as other meditative techniques) compared to active control conditions that, analogous to placebos in pharmaceutical trials, provide non-specific treatment ingredients (e.g., expectancy; Goyal et al., 2014). While mindfulness meditation programs showed effects on anxiety, depression, and pain when compared with non-specific treatment controls, there was no evidence that these treatments were superior to specific active controls (i.e., other active treatments).

The current meta-analysis was intended to further interrogate the findings of Goyal et al. (2014). We conducted a comprehensive meta-analysis of RCTs examining the effects of mindfulness-based interventions on disorder-specific symptoms across psychiatric populations. Rather than restrict our sample to certain types of comparison conditions, we aimed to evaluate empirically the degree to which outcomes are influenced by the characteristics of the control group. A more nuanced comparison to type of control condition may provide clinicians important information regarding when a mindfulness intervention should be favored compared to other known interventions. While other comprehensive meta-analyses have suggested that mindfulness-based interventions can impact clinical outcomes (e.g., anxiety, depression; Khoury et al., 2013), and several meta-analyses have examined the evidence for specific psychiatric conditions (e.g., Attention Deficit and Hyperactivity Disorder [ADHD]; Cairncross & Miller, 2016), no published comprehensive meta-analytic review has examined effects on disorder-specific symptoms across psychiatric conditions. Our study sought to examine: (1) the degree to which mindfulness-based interventions compare with a variety of control conditions, including treatments with established efficacy (i.e., evidence-based treatments); (2) for which specific disorders mindfulness-based interventions appear most efficacious, and (3) potential sources of bias.