Ultrasound & biofeedback · graded by use, two uses
HRV Biofeedback
Self-reported anxiety, HRV biofeedback (resonance breathing) training.
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How this letter has changedLatest: October 2026 · Corrected.
The B rested on Goessl et al. (Psychol Med, 2017; PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 28478782), described as consistent randomized evidence; its abstract does not say the studies were randomized. A PubMed search found Lehrer et al. (Appl Psychophysiol Biofeedback, 2020; PMID 32385728), restricted to randomized controlled studies, and a sham-controlled trial, Minjoz et al. (Biol Psychol, 2026; PMID 41905438). Anxiety holds B on those. Stress is graded C because Vann-Adibe et al. (2026; PMID 41310318) found no pooled effect. A sleep-tracker validation study was removed; it never concerned biofeedback.PMID 28478782 PMID 32385728 PMID 41905438 PMID 41310318
The record carried a not-replicated flag while its B rested on a pooled analysis of randomized trials (Goessl et al., Psychol Med, 2017; PMID 28478782). The flag describes a single trial nobody has repeated; a meta-analysis A study that pools the numbers from several trials into one combined estimate. of independent randomized trials is replication The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away. by definition, and what caps this letter at B is the endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score., not the absence of a second trial. Flag removed, letter unchanged. Applied the written grade definition under the editor's standing instruction of October 2026 (Arnold Sandlow, D.C.).PMID 28478782
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HRV biofeedback is training in slow breathing at a personal pace while a screen shows how the heart rhythm responds. A pooled review of 58 studies and a trial against a fake version both found that people said they felt less anxious. Those results come from people rating their own feelings. For everyday stress, the pooled studies disagree. One large review found no clear effect on stress, while an older one found a large effect from studies that may not have used fair comparisons.
The B belongs to one of the two uses graded on this record. The other one carries its own letter.
As studied, and the trials
Lehrer et al. (Appl Psychophysiol Biofeedback, 2020; PMID 32385728) and Minjoz et al. (Biol Psychol, 2026; PMID 41905438). Self-report caps the letter at B.
As studied, and the trials
Vann-Adibe et al. (Appl Psychophysiol Biofeedback, 2026; PMID 41310318) found no significant effect on stress; Goessl et al. (Psychol Med, 2017; PMID 28478782) found a large effect from studies not stated to be randomized. Mixed: C.
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See the full evidence record →Graded on Self-reported anxiety.
Why this gradeThe reasoning, and what the grade does not cover.
Grade B on self-reported anxiety. A meta-analysis of randomized controlled studies (Lehrer et al., 2020; PMID 32385728) and a sham-controlled trial (Minjoz et al., 2026; PMID 41905438) agree.
WHY NOT Aself-reported anxiety caps the grade.
WHAT THIS GRADE DOES NOT COVERperceived stress, where the pooled results disagree and the use is graded C; wearable accuracy; and clinical cardiovascular outcomes.
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Each use, with its trials
This record carries a separate letter for each thing it has been measured on. The headline grade is the best of them, and it does not transfer to the others.
Lehrer et al. (Appl Psychophysiol Biofeedback, 2020; PMID 32385728) and Minjoz et al. (Biol Psychol, 2026; PMID 41905438). Self-report caps the letter at B.
Vann-Adibe et al. (Appl Psychophysiol Biofeedback, 2026; PMID 41310318) found no significant effect on stress; Goessl et al. (Psychol Med, 2017; PMID 28478782) found a large effect from studies not stated to be randomized. Mixed: C.
The evidence, in fullFour papers, each linked to its PubMed record.
Lehrer et al. (Applied Psychophysiology and Biofeedback, 2020; PMID 32385728): meta-analysis restricted to randomly controlled studies, 58 included; HRV biofeedback beat both inactive and active controls, with the largest effects on anxiety, depression and anger. Minjoz et al. (Biological Psychology, 2026; PMID 41905438): 47 adults, HRV biofeedback against sham biofeedback; psychological distress improved. Goessl et al. (Psychological Medicine, 2017; PMID 28478782) pooled 24 studies, 484 participants, not stated to be randomized, and found a large reduction in self-reported stress and anxiety. Vann-Adibe et al. (Applied Psychophysiology and Biofeedback, 2026; PMID 41310318): remote HRV biofeedback, 18 studies; no significant effect on stress. Grade B on self-reported anxiety, which caps at B.
Resting HRV (RMSSD) using a validated device (Polar H10, Whoop, Oura) at baseline and monthly. The PSS-10 or STAI at baseline and 8 weeks for stress and anxiety endpoints. Resonance frequency breathing is occurring during sessions: this varies between 4.5 and 7 breaths/minute and must be identified individually.
Evidence notes: meta-analysis, randomized trial
Endpoint graded: Self-reported anxiety (self_report)
Last reviewed: October 2026
Educational use only · Not medical advice · EBL grades published human evidence and does not recommend treatment. Stopping a prescription is a decision for your physician.
Primary evidenceFour papers, each linked to its PubMed record.
Lehrer et al. (Applied Psychophysiology and Biofeedback, 2020; PMID 32385728): meta-analysis restricted to randomly controlled studies, 58 included; HRV biofeedback beat both inactive and active controls, with the largest effects on anxiety, depression and anger. Minjoz et al. (Biological Psychology, 2026; PMID 41905438): 47 adults, HRV biofeedback against sham biofeedback; psychological distress improved. Goessl et al. (Psychological Medicine, 2017; PMID 28478782) pooled 24 studies, 484 participants, not stated to be randomized, and found a large reduction in self-reported stress and anxiety. Vann-Adibe et al. (Applied Psychophysiology and Biofeedback, 2026; PMID 41310318): remote HRV biofeedback, 18 studies; no significant effect on stress. Grade B on self-reported anxiety, which caps at B.
Products carry no letter. The letter belongs to the therapy as the trials studied it, and no trial tested these products unless the entry says so. Listed alphabetically; payment does not affect order.
HRV coherence biofeedback trainer. Multiple human RCTs Randomized controlled trial: people are assigned to the treatment or a comparison by chance, so the groups differ only in what they received. It is the design that can show cause and effect. support HRV biofeedback for stress resilience, autonomic balance, and well-being, including a JAMA Network Open RCT in coronary artery disease patients and the HRV-ER trial using brain imaging. Graded B: consistent human RCT evidence with physiological/biomarker A measurable sign in the body, such as a blood test value, used to track a condition or the effect of a treatment. endpoints (HRV metrics), not hard endpoints An outcome that matters directly to a person and is counted without judgment, such as death, heart attack, stroke or fracture.. Best for stress, autonomic regulation, and recovery protocols. PMIDs: 41118163 (JAMA Network Open RCT), 36109422 (HRV-ER imaging trial).
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How EBL searched for the trials (1 search)
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("heart rate variability biofeedback"[tiab] OR "HRV biofeedback"[tiab] OR "resonance frequency breathing"[tiab]) AND (anxiety[tiab] OR stress[tiab]) AND (meta-analysis[pt] OR randomized controlled trial[pt])Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →