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Research Library
What the studies say, one question at a time
The Notes at the back of the book cover every study the book leans on. This library goes further: the research the book didn’t need, the trials published since, and the questions readers keep asking. Every entry was checked against the paper itself, sample sizes left in.
How to read the labels
A meta-analysis pools many trials; a randomized trial assigns people by chance; a lab study measures a mechanism in a few volunteers. The sample size sits next to every study because it changes how much weight a finding can carry. None of this is medical advice; read Before you begin first.
Calm, stress and mood
Which breathing practices actually reduce stress, and what makes them fail?
A 2023 review of 58 trials found most worked, and the ones that didn't shared four avoidable mistakes.
ScienceDoes breathing with a heart-rate monitor (HRV biofeedback) help anxiety or depression?
Three meta-analyses say yes, with large effects for anxiety and medium for depression, though many trials lack a strong comparison group.
PromisingWhy does breathing training help panic, and does it have to be slow?
In panic disorder, the trials point at carbon dioxide, not breathing rate: raising CO2 back to normal is what tracked the improvement.
PromisingCan a breathing practice help PTSD?
Two veteran trials of a breathing-based meditation (SKY) found real reductions, including one head-to-head where it held its own against a standard therapy.
PromisingCan a breathing practice help depression?
Two small trials of structured yogic breathing in diagnosed depression showed meaningful drops, one in people who hadn't responded to antidepressants.
PromisingCan a breathing pattern create an emotion, not just calm one down?
In a classic two-part experiment, yes: people who breathed in the pattern of joy, anger, fear or sadness, without knowing why, reported feeling it.
The body
Does slow breathing lower blood pressure?
Yes, modestly: about 5 points systolic across 17 trials, with a caution about who paid for the early studies.
MixedDoes slow breathing reduce pain?
A little, and only when it is relaxed rather than effortful; mindfulness beats breathing alone in the biggest comparison, and a four-minute cyclic sigh eased pain in a real waiting room.
PromisingDoes slow breathing before bed help insomnia?
A small study says twenty minutes of paced breathing shortened time to fall asleep and cut awakenings; the first-line treatment for insomnia is still CBT-I.
ScienceDoes breathing retraining help asthma?
It improves quality of life in a 655-person trial and a Cochrane review, and does nothing measurable to lung function. Both halves matter.
PromisingDoes slow breathing work differently as you get older?
One study says it may work better: a single session raised vagal activity more in adults over sixty than in the young, and lowered anxiety in both.
PromisingDoes a few minutes of slow breathing sharpen thinking?
Three trials say yes for working memory and decision quality, from two minutes to eight weeks of practice.
Techniques and methods
Does a longer exhale do anything a slow breath alone doesn't?
Yes, in two lab studies: the exhale-to-inhale ratio changed how relaxed people felt and how their heart rhythm responded, independent of pace.
PromisingIs box breathing better than a plain long exhale under pressure?
In the one direct comparison, box breathing calmed the body a little more at rest, but the long exhale produced better performance on the task.
PromisingWhat is "resonance frequency" breathing, and does the exact rate matter?
It's the pace, near six breaths a minute, where your heart rhythm swings most; one study found breathing at your own rate beat breathing one breath a minute faster.
MixedWhat does the research say about the Wim Hof Method?
A 2024 systematic review of eight trials: a real effect on inflammatory markers, mixed results for performance, and nothing yet on the health outcomes people buy it for.
Last reviewed October 2026. The book’s own sources, chapter by chapter, are in the Notes. Missing a study that should be here? Use the contact form.
From the book
This page is part of the companion site for The Joyful Exhale: Breathing Under Pressure by Eric Bradley, a Los Angeles studio singer and voice actor with more than thirty years behind the microphone.
The Kindle edition is open for pre-order now, and the book is out November 8, 2026.
Cite this page: Eric Bradley, “Breathing research library: what the studies say,” The Joyful Exhale, https://joyfulexhale.com/research/