The book's Chapter 8 explains that the urge to breathe tracks carbon dioxide, and that chronically over-breathing drives CO2 low and makes the body feel like something is wrong. A series of trials from Alicia Meuret's group tested that idea directly in people with panic disorder, using a small device that measures end-tidal CO2 so patients could see it and learn to bring it up.
In the first trial, 37 people with panic disorder were randomized to four weeks of this training or a delay. Panic severity, agoraphobic avoidance, anxiety sensitivity, and disability improved in the treated group with moderate-to-large effects, and held at follow-up. A second analysis of 35 patients found that changes in CO2, and not changes in breathing rate, partly mediated the drop in fear of bodily sensations; earlier CO2 predicted later fear, not the reverse. A third trial of 41 patients compared the breathing training against cognitive training and found both worked about equally on symptoms, but only the breathing training corrected CO2 from low to normal, and CO2 change preceded the symptom change in that arm.
Two things follow. First, "breathe slower" is not quite the instruction; "breathe less, and let the CO2 come back" is closer, which is what a long, unforced exhale does. Second, these are small trials of a specific protocol with a monitor. The book's CO2 Alarm page explains the mechanism and the gentle, no-device version. Panic disorder itself is treated by professionals, and the book says so.
The studies
Meuret AE, Wilhelm FH, Ritz T, Roth WT. Feedback of end-tidal pCO2 as a therapeutic approach for panic disorder. Journal of Psychiatric Research 42(7), 2008, 560–568. Read the abstract
- Sample
- 37
- Design
- Randomized to four weeks of capnometry-assisted breathing training or delayed treatment.
- Found
- Significant improvement in panic severity, avoidance, anxiety sensitivity, disability and respiratory measures in the treated group, moderate-to-large effects, maintained at follow-up.
- Limits
- Preliminary, small, delayed-treatment control.
Meuret AE, Rosenfield D, Hofmann SG, Suvak MK, Roth WT. Changes in respiration mediate changes in fear of bodily sensations in panic disorder. Journal of Psychiatric Research 43(6), 2009, 634–641. Read the abstract
- Sample
- 35
- Design
- Longitudinal mediation analysis within the breathing-training treatment.
- Found
- CO2, not respiration rate, partially mediated reductions in anxiety sensitivity; earlier CO2 predicted later fear and not the reverse.
- Limits
- Single-arm mediation analysis.
Meuret AE, Rosenfield D, Seidel A, Bhaskara L, Hofmann SG. Respiratory and cognitive mediators of treatment change in panic disorder: evidence for intervention specificity. Journal of Consulting and Clinical Psychology 78(5), 2010, 691–704. Read the abstract
- Sample
- 41
- Design
- Randomized to four weeks of breathing training or cognitive training.
- Found
- Both reduced panic severity comparably; only breathing training normalized CO2, and CO2 change preceded symptom change in that arm.
- Limits
- Small; four-week protocols.
Where this lands in the book
Techniques
Rooms
Two rules, no exceptions
Never practice any technique on this site while you are driving, operating machinery, or doing anything that needs your full attention. The slow ones can make you drowsy, faster than you’d expect. And never practice a breath-hold, bellows breath, or any vigorous breathing in or near water. Read Before you begin for the doctor’s list and the rest.
Verdict scale: Science means trials or meta-analyses with consistent findings; Promising means real trials that are small, few, or unreplicated; Mixed means the studies point both ways; Mechanism means it shows how something works in the body, not that it helps in life. Checked against the published abstracts in October 2026. Not medical advice.