Acceptance lowers stress reactivity: Dismantling mindfulness training in a randomized controlled trial

Training in both monitoring present-moment experience and accepting it reduces biological stress reactivity, whereas monitoring alone does not. In a randomized trial, 153 stressed adults completed one of three 15-lesson smartphone-based trainings: Monitor+Accept, Monitor Only, or an active Coping control. After training, a social stress test showed that Monitor+Accept training lowered cortisol and systolic blood pressure reactivity compared to the other two conditions. Subjective stress levels were moderate across all groups. The findings indicate that acceptance is a key mechanism driving mindfulness-related stress reduction effects on biology.

Study at a glance

Abstract

Objective: Mindfulness interventions, which train practitioners to monitor their present-moment experience with a lens of acceptance, are known to buffer stress reactivity. Little is known about the active mechanisms driving these effects. We theorize that acceptance is a critical emotion regulation mechanism underlying mindfulness stress reduction effects. Method: In this three-arm parallel trial, mindfulness components were dismantled into three structurally equivalent 15-lesson smartphone-based interventions: (1) training in both monitoring and acceptance (Monitor+Accept), (2) training in monitoring only (Monitor Only), or (3) active control training (Coping control). 153 stressed adults (mean age = 32 years; 67% female; 53% white, 21.5% black, 21.5% Asian, 4% other race) were randomly assigned to complete one of three interventions. After the intervention, cortisol, blood pressure, and subjective stress reactivity were assessed using a modified Trier Social Stress Test. Results: As predicted, Monitor+Accept training reduced cortisol and systolic blood pressure reactivity compared to Monitor Only and control trainings. Participants in all three conditions reported moderate levels of subjective stress.Conclusions: This study provides the first experimental evidence that brief smartphone mindfulness training can impact stress biology, and that acceptance training drives these effects. We discuss implications for basic and applied research in contemplative science, emotion regulation, stress and coping, health, and clinical interventions.