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Mechanisms of change in peer coaching for digital ACT: A serial mediation model on program adherence and psychological flexibility's role in reducing distress

Journal of Contextual Behavioral Science (JCBS)
Volume 37, July 2025

Authors

Korena S. Klimczak, Michael P. Twohig, Gretchen G. Peacock, & Michael E. Levin

Key Findings

  • Phone and text coaching's effects on mental health are mediated by program adherence.
  • Phone coaching can boost psychological flexibility independently of program adherence.
  • Text coaching has a small direct effect on psychological distress.

Abstract

Background 

Coaching is a well-supported intervention for improving adherence to online mental health programs. It is currently unclear whether peer-support coaching improves mental health outcomes solely through improving program adherence, or if it can also have a direct impact on mental health. We investigated this using a randomized controlled trial and applying serial mediation models. 

Method 

A total of 230 college students were instructed to use the 12-session ACT Guide program over 10 weeks. They were randomly assigned to additionally receive either peer-support coaching over weekly phone calls, text message conversations, or a no-coaching control group. Coaching followed a standardized protocol. 

Results 

Phone coaching had a significant total effect, but not a direct effect, on psychological distress. Both the phone coaching → psychological flexibility → distress, and the phone coaching → program adherence → psychological flexibility → distress indirect pathways were significant. Text coaching had a significant total and direct effect on psychological distress. The full serial pathway was the only significant indirect effect (text coaching → program adherence → psychological flexibility → distress). 

Conclusions 

We found that peer coaching in both formats significantly increased program adherence, which in turn improved psychological flexibility, consequently reducing psychological distress. Coaching through phone calls had a significantly greater indirect effect on distress and direct effect on program adherence in comparison to the text message format. It is possible that the skills review and ACT-based strategies used in phone coaching directly improve psychological flexibility regardless of the number of modules completed, with text coaching being too brief to elicit this same effect.

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