Distress tolerance as a mediator of mindfulness-based intervention for anxiety and depression: Evidence from two randomized controlled trials

Objective: We aimed to investigate whether distress tolerance mediated the effects of mindfulness-based intervention (MBI) on anxiety and depression with two randomized controlled studies. Method: In Study 1, 374 participants with at least moderate emotional distress were randomized to an intervention group (N = 174) and a waitlist control group (N = 173). Mindfulness, distress tolerance, anxiety, and depression were measured at the pre-test, week 3, week 5, and post-test. In Study 2, 170 participants with emotional disorders were randomized to an intervention group (N = 86) and a control group (N = 84). The same variables were assessed at pre-test, weekly during the intervention, and post-test. Results: In both studies, linear mixed effect models showed that compared to the control group, mindfulness, distress tolerance, anxiety, and depression significantly improved in the intervention group. Parallel process latent growth curve models showed that changes in distress tolerance mediated the effects of the MBI on changes in anxiety and depression. Random-intercept cross-lagged panel models found that distress tolerance temporally preceded depression, but not anxiety. Conclusions: Distress tolerance is a potential mechanism underlying MBIs. Interventions targeting distress tolerance could be embedded in MBIs to enhance the intervention effects for emotional distress.