Background: Mindfulness meditation (MM) is a commonly used psychological intervention for pain, mood, and anxiety conditions, but can be challenging to practice with severe symptoms without proper training. The Mindfulness Meditation app (MMA) is a supportive training tool specifically developed for this study to aid in the practice of mindful breathing using a smartphone.

Objective: This study aims to evaluate the psychophysiological effects of the MMA. Specifically, the study will assess parasympathetic functioning using heart rate variability (HRV; primary outcome), pain and mood symptoms, mind-wandering and present moment awareness, and breath focus in groups of undergraduate participants who self-report clinically-relevant symptoms of chronic pain (CP) and depression or anxiety (DA) and condition-free (CF) participants who do not meet either criteria. We hypothesize that use of the MMA by study groups will lead to improved HRV, pain, and mood symptoms compared with groups who do not use the app.

Methods: This study is a two-arm randomized controlled trial (RCT) recruiting through a Web-based research participation pool at York University in Toronto, Canada. We are aiming for minimum 60 participants in each of CP, DA, and CF groups. Upon arriving to the laboratory, participants will be prescreened for classification into groups of CP, DA, or CF. Groups will be randomly assigned by a 1:1 ratio to an MMA (MMA+) condition or MM condition without the app (MMA-) after a brief stress induction procedure. In MMA+, participants will practice mindful breathing with a smartphone and press breath or other buttons at the sound of audio tones if their awareness was on breathing or another experience, respectively. HRV and respiration data will be obtained during rest (5 min), stress induction (5 min), and meditation conditions (12 min). Participants will complete psychological self-report inventories before and after the stress induction and after the meditation condition. Separate linear mixed models will be used to examine HRV and self-report inventories comparing groups and treatment conditions.

Results: Recruitment for the study began in November 2017 and is expected to be completed in winter of 2019-2020. As of July 2019, 189 participants have been recruited. The study's main findings are expected to reveal a positive pattern of HRV responses in the CP, DA, and CF groups, such that a significant increase in HRV (P<.05) is detected in those randomized to the MMA+ condition in comparison with those randomized to the MMA- condition.

Conclusions: This RCT will contribute to the burgeoning health psychology literature regarding the clinical relevance of HRV in assessment and treatment of psychological and medical conditions. Furthermore, possible ways to inform designs of MM training tools delivered by apps and Web platforms for CP, depression, and anxiety conditions' treatment will be discussed.

Trial registration: Clinicaltrials.gov NCT03296007; https://clinicaltrials.gov/ct2/show/NCT03296007.

International registered report identifier (irrid): DERR1-10.2196/14119.