The review, led by Marc-Olivier Mainville and Philippe Fournier at Université Laval in Québec City, along with colleagues in Canada and France, set out to map every study that had examined heart rate variability biofeedback in veteran-only populations for these three chronic conditions. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews, the team searched PubMed, Embase, and CINAHL in August 2024, with an updated search in February 2025. Of 69 records identified, only five studies met the inclusion criteria, encompassing a total of just 108 participants. Four of the studies were pilot studies with control groups, and sample sizes ranged from a mere 12 to 35 participants each.

The scientific rationale behind heart rate variability biofeedback is rooted in the autonomic nervous system, the branch of physiology that governs involuntary bodily functions such as heart rate, digestion, and stress responses. Heart rate variability — the natural variation in the time intervals between successive heartbeats — serves as a non-invasive window into autonomic regulation, particularly the balance between the sympathetic system, which drives the fight-or-flight response, and the parasympathetic system, which promotes calm and recovery. In a typical biofeedback session, individuals breathe at their so-called resonance frequency, usually around six breaths per minute, with exhalations slightly longer than inhalations, roughly 5.5 seconds out and 4.5 seconds in. This paced breathing stimulates the baroreflex, a key blood-pressure regulatory mechanism, and enhances vagal activity, which is reflected in increased heart rate variability. Proponents argue that repeated practice can improve emotional regulation, stress resilience, and physiological flexibility.

The connection to veterans’ chronic conditions is more than speculative. Post-traumatic stress disorder has been repeatedly associated with reduced parasympathetic, or vagal, activity, and meta-analytic evidence confirms autonomic dysfunction indexed by heart rate variability in PTSD. Chronic pain shows a similar pattern, with a meta-analysis of studies in pain patients finding decreased heart rate variability that implicates parasympathetic dysregulation. Chronic pain-related activation of the body’s stress response has been linked to reduced heart rate variability power and lower resilience and self-regulatory capacity. Tinnitus, by contrast, presents a murkier picture: evidence linking the phantom sound perception to autonomic nervous system dysfunction remains limited and inconsistent, though some studies have reported associations between autonomic imbalance and tinnitus-related distress.

What did the five studies actually find? Four examined heart rate variability biofeedback in relation to PTSD symptoms, with mixed results. Two reported improvements in overall PTSD symptoms, and one of these found that the benefits persisted 16 weeks after the end of training. One study reported reductions limited to intrusion symptoms — the intrusive memories, dreams, and flashbacks that characterize one cluster of PTSD — while another found that biofeedback was not significantly more effective than standard care. The sole study to measure depressive symptoms alongside PTSD reported meaningful decreases in depression. A single pilot study, conducted at a U.S. Department of Veterans Affairs medical center, examined chronic pain and reported significant reductions in perceived pain, perceived stress, negative emotions, and physical activity limitations following four weeks of weekly biofeedback sessions. All four studies that measured heart rate variability reported that the intervention increased it at rest.

Yet the researchers urge strong caution in interpreting these findings. The studies were small, methodologically heterogeneous, and used wildly different approaches to measuring heart rate variability. Some relied on electrocardiography, others on photoplethysmography or blood volume pulse sensors attached to the finger, wrist, or forearm. The metrics used to quantify variability differed across studies, including the coherence ratio, the root mean square of successive differences between normal heartbeats, the standard deviation of inter-beat intervals, and high- and low-frequency power. Non-ECG methods are more susceptible to peak-detection errors and may artificially inflate or attenuate variability estimates, while lower sampling rates can obscure the high-frequency, vagally mediated components of the signal. In some cases, it was unclear whether changes in treatment groups actually differed significantly from changes in control groups, because the statistical analyses were not fully presented.

There is a deeper physiological puzzle as well. The review highlights that reported increases in heart rate variability may reflect transient responses during paced breathing — reductions in heart rate and short-term shifts in parasympathetic activity — rather than sustained changes in autonomic regulation. Because vagal modulation of the heart’s pacemaker operates rapidly, increases in beat-to-beat variability are more pronounced at lower heart rates and may simply occur as individuals enter a more relaxed state, rather than representing a specific therapeutic mechanism. Notably, none of the five studies examined the statistical relationship between changes in heart rate variability metrics and improvements in clinical symptoms, leaving open the question of whether the physiological changes are a mechanism of action or merely a non-specific correlate of feeling calmer.

The tinnitus gap is perhaps the most striking finding of the review. Despite tinnitus being the most prevalent service-connected disability among U.S. veterans, and despite its frequent co-occurrence with PTSD — one study found that 34 percent of the first 300 patients enrolled in the Veterans Affairs Medical Center Tinnitus Clinic also had a PTSD diagnosis — no studies have ever investigated heart rate variability biofeedback in relation to tinnitus in veterans. Large-scale cohort data involving more than 570,000 Iraq and Afghanistan veterans receiving care through the U.S. Department of Veterans Affairs found that PTSD alone was significantly associated with hearing loss and tinnitus, with veterans in this group having greater odds of tinnitus than those without PTSD, depression, or traumatic brain injury. Several pain-related conditions, including headache, neck pain, and jaw pain, were also associated with tinnitus. In the general population, only a single publication, covering three case studies, reported a potential effect of the technique on tinnitus handicap — and only in one of the three tested patients.

The rationale for exploring the technique in veterans is strengthened by clinical guidelines. The Veterans Affairs/Department of Defense guidelines for managing chronic conditions emphasize the underutilization of non-pharmacological interventions, which may provide symptom relief while reducing the risks associated with polypharmacy — a significant concern in veteran populations, where high rates of multimorbidity and medication use are common. The review also points to evidence that evidence-based PTSD psychotherapies produce measurable changes in psychophysiological responses, including reduced trauma-potentiated startle and altered heart rate reactivity, providing additional rationale for investigating interventions that target physiological processes directly.

Despite the limitations, the review highlights the feasibility of studying heart rate variability biofeedback in veterans with chronic conditions. The intervention is non-invasive, requires minimal equipment, and has not been associated with any adverse effects — none of the reviewed studies reported negative side effects. Several studies reported some level of improvement in the targeted chronic condition, and it is plausible that additional, unmeasured benefits may have occurred, although this remains to be validated. The authors conclude that the current evidence does not allow conclusions regarding the technique’s efficacy as a standalone intervention for PTSD or chronic pain, although it may have potential as an adjunctive or supportive approach. They call for rigorously designed, adequately powered studies to evaluate the feasibility, safety, and potential relevance of the technique in well-characterized veteran populations, including those with tinnitus and co-occurring conditions — and they stress that future research should avoid assuming shared underlying mechanisms across conditions, instead adopting designs that account for clinical heterogeneity, individual differences, and tinnitus subtypes.

Subject of Research: Heart rate variability biofeedback for tinnitus, PTSD, and chronic pain in veterans

Article Title: Heart rate variability biofeedback and implications for tinnitus, PTSD and chronic pain in veterans: a scoping review

Article References: Mainville, M.-O., Lacasse-Rioux, É., Noreña, A. J., Vallet, G. T., & Fournier, P. (2026). Heart rate variability biofeedback and implications for tinnitus, PTSD and chronic pain in veterans: a scoping review. Frontiers in Audiology and Otology, 4, Article 1917408. https://doi.org/10.3389/fauot.2026.1917408

Image Credits: AI Generated

DOI: 10.3389/fauot.2026.1917408

Keywords: heart rate variability biofeedback, veterans, PTSD, tinnitus, chronic pain, autonomic nervous system, vagal activity, non-pharmacological intervention, scoping review, paced breathing, baroreflex, polypharmacy