Eligible for inclusion were randomised controlled trials of face-to-face group interventions, where mindfulness represented a core part of therapy and daily practice was encouraged between sessions. Eligible participants had to be 18 year or older, and had to meet full diagnostic criteria for a current episode of DSM-IV (Diagnostic and Statistical Manual of mental disorders version four or later) or ICD-10 (International Classification of Diseases-10) anxiety or depressive disorder (specific disorders were listed in the paper). Eligible outcomes were psychometrically reliable and valid measures of depression or anxiety. Trials of participants with cognitive impairment or of those engaged in substance misuse were excluded.
Included participants had a DSM-IV confirmed diagnosis of a major depressive disorder or an anxiety disorder (which covered social anxiety, generalised anxiety, post-traumatic stress disorder, health anxiety, or a range of anxiety disorders). Mean ages of participants ranged from 21 to 52 years. Most studies reported some use of psychotropic medication.
Most interventions were Mindfulness-Based Cognitive Therapy or Mindfulness-Based Stress Reduction (eight 2-3 hour weekly sessions plus one whole day session); one study used Person-Based Cognitive Therapy (twelve 90-minute sessions). Active control groups received cognitive behavioural therapy or group psycho-education. Inactive control groups received treatment as usual, aerobic exercise, or were on a waiting list.
Primary outcomes were symptom severity for the target clinical problem. Secondary outcomes were anxiety and depression symptom severity (irrespective of diagnosis).
The authors did not state how many reviewers selected the studies for inclusion.