There was a large, significant effect for anxiety in 10 before-and-after studies (Hedges' g 0.89, 95% CI 0.71 to 1.08 I²=14%), and four waiting-list controlled studies (Hedges' g 0.96, 95% CI 0.67 to 1.24). There were no significant differences between mindfulness-based therapy and traditional cognitive-behavioural therapy or other behavioural therapy (nine studies), or pharmacological treatments (three studies).Īnalysing before-and-after and waiting-list controlled studies separately, at the end of treatment the effect sizes for mindfulness-based therapy were larger for treatment for psychological disorders, than for physical or medical conditions. Attrition ranged from none to 81.5%.įor clinical outcomes, at the end of treatment, mindfulness-based therapy was significantly more effective than psychological education (Hedges' g 0.61, 95% CI 0.27 to 0.96 nine studies I²=83%), supportive therapy (Hedges' g 0.37, 95% CI 0.17 to 0.57 seven studies I²=64%), relaxation procedures (Hedges' g 0.19, 95% CI 0.03 to 0.35 eight studies I²=59%), and imagery or suppression techniques (Hedges' g 0.26, 95% CI 0.10 to 0.53 two studies I²=0). In studies with follow-up, it ranged from three weeks to three years.
The before-and-after studies had a mean quality score of 2.93 (out of 5). The controlled studies had a mean quality score of 4.84 (out of 11).
There were 209 studies, with 12,145 participants 109 were randomised controlled trials (RCTs), 26 were non-randomised controlled studies, 72 were uncontrolled before-and-after studies, and two only reported follow-up data. Disagreements were resolved through discussion, or by contacting the original study's authors. One reviewer selected studies for inclusion and decisions were checked by a second reviewer. Outcomes were measured by a variety of instruments (details in the paper). Many studies included more than one disorder. The most common disorders were mood and cancer (some studies included caregivers), anxiety, pain, alcohol or substance abuse, fibromyalgia, overweight or obesity, social anxiety or social phobia, HIV, post-traumatic stress disorder, and headache. Controlled studies used either a treatment or waiting list, as the control. In the included studies, a variety of mindfulness therapies were used, including mindfulness-based awareness processes, stress reduction, cognitive therapy, relapse prevention and yoga. Studies had to report sufficient information to calculate effect sizes for clinical (physical or psychological) or mindfulness outcomes. Studies were excluded if they compared mediation styles or mediators, examined the non-direct effects of mindfulness, used mindfulness as a component of another treatment, or were based on meditation instruction, induction or retreats. Eligible was any study evaluating the before-and-after or controlled effects of mindfulness-based therapy for physical or medical conditions, for psychological disorders, or for a non-clinical population.