Four controlled trials were included in the review (n=239): three randomised controlled trials of recovered recurrently depressed patients and one non-randomised trial of patients with residual symptoms of depression. The Jadad scores ranged from 0 to 2 out of a maximum possible 4 points.
For patients with three or more previous major depressive episodes, relapse hazard rates were statistically significantly lower for the mindfulness-based cognitive therapy plus usual treatment group than in the usual treatment alone group in the two better-quality randomised controlled trials. There were no statistically significant differences in relapse or recurrence hazard rates for patients with two previous major depressive episodes.
The other randomised controlled trial was based on a subset of data from one of the previously described randomised controlled trials. It found no significant effect of mindfulness-based cognitive therapy on Hamilton Rating Scale for Depression scores. Patients who received mindfulness-based cognitive therapy in addition to usual treatment experienced a greater shift away from categoric memories and a greater increase in specific memories (indicating a shift away from a cognitive-style thought to be characteristic of depression). The trial also reported no significant differences between groups in latency to respond or omitting to respond in the Autobiographical Memory Test.
The non-randomised controlled trial found no significant difference between groups in change in Rumination Scale scores. There was a greater pre- and post-treatment reduction in Beck Depression Inventory scores in the mindfulness-based cognitive therapy plus usual treatment group compared with the usual treatment alone group.