A Randomized Controlled Trial of an Online Self-Help Mindfulness Intervention for Emotional Distress: Serial Mediating Effects of Mindfulness and Experiential Avoidance

Objectives Internet-based self-help Mindfulness Intervention for Emotional Distress (iMIED) program is a newly developed program targeting essential transdiagnostic factors underlying emotional distress, the effects of which have gained initial support in sub-clinical samples. The current study investigated its effects on the underlying mechanisms by examining mindfulness and experiential avoidance as putative mediators.Method Patients with emotional disorders were recruited online. After interviews, 75 patients were randomly allocated to either iMIED (n = 37) including treatment as usual (TAU) or TAU-only control group (n = 38). Mindfulness, experiential avoidance, and emotional distress (i.e., anxiety, depression, and general emotional distress) were measured before (T0) and after the intervention (T8). During the intervention period, mindfulness was measured weekly (T1-T7); experiential avoidance was measured at Week 2 (T2) and Week 5 (T5).Results Intention-to-treat 2 x 2 repeated-measures ANOVAs showed that, compared with the TAU-only group, mindfulness, experiential avoidance, and emotional distress significantly improved in the iMIED + TAU group (Cohen's d = 0.53-0.79). Latent growth curve analyses showed that more than half of the improvement in mindfulness and experiential avoidance occurred at T3 and T5, respectively. Serial mediation analyses found that mindfulness at T3 and experiential avoidance at T5 sequentially mediated the effects of the iMIED program on emotional distress.Conclusions The current study, using a randomized controlled trial with multiple time-point measurements, demonstrated that the iMIED program offers a scalable approach for the management of emotional distress by increasing mindfulness and decreasing experiential avoidance.