Encouraging Breath: Increasing Out‑of‑Session DMHI Engagement using a Shape‑Changing Biofeedback Physicalization within a Longitudinal RCT

Paper Title

Encouraging Breath: Increasing Out‑of‑Session DMHI Engagement using a Shape‑Changing Biofeedback Physicalization within a Longitudinal RCT

Publication Info

• Topic area: Enhancing engagement in Digital Mental Health Interventions (DMHIs) through biofeedback-based physicalization.
• Keywords: Digital Mental Health Interventions, biofeedback, shape-changing interfaces, mindfulness, engagement, adherence, interoception, well-being, randomized controlled trial, embodied cognition.

Background and Problem

• Problem / challenge: Adherence to out-of-session DMHI practices is low, with engagement dropping by 96.1% within two weeks. Existing biofeedback designs often fail to sustain meaningful engagement or support long-term adherence.
• Significance: Improving adherence to DMHIs can enhance therapeutic outcomes, reduce mental health treatment costs, and support habit formation in mindfulness practices.
• Motivation and related work: Prior research highlights the potential of biofeedback and shape-changing interfaces for enhancing engagement, but evidence is limited to short-term effects. There is a need for empirical data on their impact over extended periods and in out-of-session contexts.

Solution

• Proposed approach: Ankor, a handheld shape-changing biofeedback physicalization, was integrated into a mindfulness DMHI to enhance out-of-session engagement.
• Novelty:
  1. Introduction of a shape-changing biofeedback device that mirrors users' breathing in real time.
  2. Longitudinal evaluation of its impact on DMHI engagement and psychological outcomes over six weeks.
  3. Empirical evidence on the role of kinaesthetic feedback in fostering sustained adherence and embodied mindfulness skills.
• Procedure and key techniques:
  • A six-week randomized controlled trial (RCT) with 69 participants divided into experimental (Ankor + audio) and control (audio-only) groups.
  • Weekly 15-minute in-lab mindfulness sessions, with optional DMHI use between sessions.
  • Ankor provided real-time tactile feedback by expanding and contracting based on users' breathing, enhancing embodied awareness.
  • Engagement was measured through app usage metrics, self-reports, and physiological data (e.g., heart rate variability).

Results

• Concrete findings:
  • Ankor users initiated 433 DMHI practices compared to 96 in the control group (351% increase).
  • By week 2, 29.4% of Ankor users remained active compared to 2.9% in the control group.
  • Significant improvements in well-being (WEMWBS: 27.3% vs. 19.4% increase) and interoceptive awareness (e.g., attention regulation, emotional awareness).
  • Enhanced physiological engagement, with higher heart rate variability (HRV) changes in the Ankor group.
• Advantage over baselines:
  • Substantially higher DMHI engagement metrics (e.g., access, initiation, completion).
  • Greater embodied mindfulness skills and interoceptive awareness compared to the control group.
• Experiments / evaluation:
  • Participants were assessed at baseline (T1), mid-intervention (T2–T5), and end-of-intervention (T6).
  • Measures included self-reports (e.g., SIMS, FSS, WEMWBS), physiological data (HRV), and app usage logs.
  • Statistical analyses (e.g., GLMs, Z-tests) confirmed significant between-group differences.
• Limitations and future work:
  • Conducted in a controlled setting with a non-clinical sample, limiting generalizability.
  • Uncertainty about whether benefits arose from increased practice frequency or improved practice quality.
  • Potential novelty effects of Ankor not fully disentangled.
  • Future work should explore diverse populations, longer durations, and disentangle specific design elements of Ankor.

Summary

This study demonstrates that integrating a shape-changing biofeedback physicalization (Ankor) into a mindfulness DMHI significantly enhances out-of-session engagement and fosters embodied mindfulness skills. Over six weeks, Ankor users showed a 351% increase in practice initiations and sustained higher engagement compared to the control group. Improvements in well-being, interoceptive awareness, and physiological engagement were also observed. These findings suggest that kinaesthetic feedback can address barriers to DMHI adherence, supporting habit formation and skill acquisition. Future research should explore broader applications and refine the design to maximize long-term impact.