Photobiomodulation, Heart Rate Variability, and Acute Stress

The Effect of Photobiomodulation on Heart Rate Variability in Healthy Adults Subjected to the Maastricht Acute Stress Test (MAST): A Sham-controlled, Within-subject Study

Photobiomodulation (PBM) is a form of light therapy that uses red or near-infrared light to influence biological processes. In prior studies, PBM has been shown to improve various physiological functions, including tissue repair, inflammation, and cognitive performance. However, little is known about its impact on autonomic nervous system regulation. Thus, the goal of this study is to evaluate the effects of PBM on vagal activity, as measured by heart rate variability (HRV), in healthy adults undergoing experimental stress.

Study Overview

• Status: Not yet recruiting
• Conditions: Stress
• Intervention / Treatment: Device: Vielight Vagus; Other: Sham Vielight Vagus

Detailed Description

Photobiomodulation (PBM) is a non-invasive therapeutic technique that uses low-level light, typically in the red or near-infrared spectrum, to stimulate biological tissues. This approach has been increasingly studied for its beneficial effects on wound healing, mood, and sleep quality. Recent research has also highlighted PBM's potential in enhancing brain function, neuroplasticity, and cognitive performance. For example, prior studies have demonstrated that transcranial PBM (i.e., PBM delivered to the head) can help modulate neuronal activity, improve cerebral blood flow, and promote neuroprotective effects for traumatic brain injury and stroke. Given these findings, PBM may also have potential for influencing autonomic function and stress physiology. However, to date, little is known about the effects of PBM on the autonomic nervous system, particularly its influence on vagal activity and heart rate variability (HRV).

This study aims to fill this gap by investigating the effects of transcutaneous cervical plus intranasal PBM on HRV in healthy individuals subjected to experimental stress. Specifically, the Maastricht Acute Stress Test (MAST) will be used, which is a validated stress protocol that has been shown to strongly and reliably induce acute autonomic stress responses. A within-subject design will be employed with four repeated visits per participant to examine the effects of both PBM and sham intervention applied before and after stress induction on vagal activity, as measured by HRV. As the first study to examine PBM's impact on HRV, this research will provide valuable insights into the potential of PBM as a novel, non-invasive approach to modulating autonomic regulation, particularly in the context of stress.

• Study Type: Interventional
• Enrollment (Estimated): 40
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Peter Wayne, PhD; Phone Number: 617-732-6271; Email: pwyane@bwh.harvard.edu
• Study Contact Backup: Name: EunMee Yang, PhD; Phone Number: 617-582-9291; Email: eyang13@bwh.harvard.edu

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• Healthy adults, aged 18-64 years
• Ability to read and understand English
• Willing to comply with the study procedures and attend all scheduled sessions

Exclusion Criteria:

• Taking medications that could significantly influence autonomic function
• Presence or history of any serious cardiovascular, inflammatory, and pain conditions as well as neurological disorders or other conditions that affect the central nervous system
• Pregnant

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Other
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Active Comparator: Real PBM before stress induction; After a 5-minute baseline measurement, participants will receive 20 minutes of real PBM. They will then complete the 15-minute MAST protocol (stress induction) and be monitored for additional 10 minutes to assess recovery from stress.	Device: Vielight Vagus; In this study, PBM will be administered using a transcutaneous cervical plus intranasal PBM device (Vielight Vagus, Ontario, Canada). The transcutaneous component of the device is designed to be placed bilaterally over the lateral aspect of the neck and delivers an irradiance of 810nm at 50mW/cm2, while the intranasal component is designed to be inserted into the nasal cavity and provides an irradiance of 810nm at 25mW/cm2. The pulse frequency will be set to 100 Hz and 50% duty cycle.
Sham Comparator: Sham PBM before stress induction; After a 5-minute baseline measurement, participants will receive 20 minutes of sham PBM. They will then complete the 15-minute MAST protocol (stress induction) and be monitored for additional 10 minutes to assess recovery from stress.	Other: Sham Vielight Vagus; For sham intervention, the same PBM device will be placed on the participants in the same manner, but without emitting light to ensure blinding of the intervention.
Active Comparator: Real PBM after stress induction; After a 5-minute baseline measurement, participants will undergo the 15-minute MAST protocol (stress induction), followed by 20 minutes of real PBM and 10 minutes of post-intervention period.	Device: Vielight Vagus; In this study, PBM will be administered using a transcutaneous cervical plus intranasal PBM device (Vielight Vagus, Ontario, Canada). The transcutaneous component of the device is designed to be placed bilaterally over the lateral aspect of the neck and delivers an irradiance of 810nm at 50mW/cm2, while the intranasal component is designed to be inserted into the nasal cavity and provides an irradiance of 810nm at 25mW/cm2. The pulse frequency will be set to 100 Hz and 50% duty cycle.
Sham Comparator: Sham PBM after stress induction; After a 5-minute baseline measurement, participants will undergo the 15-minute MAST protocol (stress induction), followed by 20 minutes of sham PBM and 10 minutes of post-intervention period.	Other: Sham Vielight Vagus; For sham intervention, the same PBM device will be placed on the participants in the same manner, but without emitting light to ensure blinding of the intervention.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in HRV, as measured by RMSSD	Root mean square of successive differences (RMSSD) is a commonly used time-domain measure of HRV. It is commonly used to assess autonomic regulation, with higher RMSSD indicating greater parasympathetic activity and vagal tone. In this study, RMSSD will be calculated for every 5-minute segments of HRV data from baseline to post-phase. The area under the curve (AUC) will be computed to assess changes in RMSSD values with respect to baseline. This approach will allow for a comprehensive evaluation of changes in parasympathetic activity, in both magnitude and variability over time under different experimental conditions. Paired t-tests will then be used to compare AUCs between PBM and sham interventions, separately for before and after stress induction.	50 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in electrodermal activity (EDA)	Similar to ECG/HRV, EDA data will be measured continuously from baseline to post-phase for 50 minutes, to provide a more comprehensive assessment of the autonomic responses.	50 minutes
Change in blood pressure (BP)	BP will be assessed every 5 minutes during each visit's study procedures.	50 minutes
Change in state anxiety	Participants will be asked to complete the state anxiety subscale of the State-Trait Anxiety Inventory (STAI) two times for each visit, initially before baseline and then during the post-phase period.	50 minutes

Collaborators and Investigators

• Sponsor: Brigham and Women's Hospital
• Collaborators: Vielight Inc.
• Investigators: Principal Investigator: Peter Wayne, Brigham and Women's Hospital

Study record dates

Study Major Dates

• Study Start (Estimated): July 1, 2026
• Primary Completion (Estimated): May 31, 2027
• Study Completion (Estimated): August 31, 2027

Study Registration Dates

• First Submitted: March 13, 2026
• First Submitted That Met QC Criteria: March 13, 2026
• First Posted (Actual): March 17, 2026

Study Record Updates

• Last Update Posted (Actual): June 2, 2026
• Last Update Submitted That Met QC Criteria: June 1, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: Stress; Photobiomodulation; Heart rate variability; Vagus nerve
• Other Study ID Numbers: 2026P000281

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No