Nineteen trials (491 patients; range 10 to 53) were included in the review. Five were randomised controlled trials (RCTs) and 14 were uncontrolled trials. Follow-up ranged from after treatment to 12 months. Attrition rates ranged from zero to 45.5%.
Mindfulness- and acceptance-based interventions statistically significantly reduced anxiety symptoms (Hedges' g 1.08, 95% CI 0.81 to 1.34; I²=61%; 18 trials) and depression symptoms (Hedges' g 0.85, 95% CI 0.66 to 1.03; I²=17%; 15 trials) after intervention. They statistically significantly improved quality of life after intervention (Hedges' g 0.65, 95% CI 0.36 to 0.93; I²=0; five trials).
The controlled trials showed that mindfulness- and acceptance-based interventions were statistically significantly more effective, at improving anxiety and depression, than controls, but there was evidence of statistical heterogeneity (I²=87% for anxiety and 67% for depression).
Separate analyses indicated that patients with panic disorder and generalised anxiety disorder reported greater improvements (Hedges' g 1.85, 95% CI 1.29 to 2.41) than patients with other anxiety disorders.
There was no evidence of publication bias in the funnel plots and fail-safe N