Intense breathwork cut blood flow to the brain’s grey matter by about 45%, a small study finds

Blood flow to the brain’s grey matter dropped by about 45% at its lowest point when 30 experienced breathwork practitioners breathed intensively inside an MRI scanner, a small study from Germany has found. The scans, taken at each person’s peak of the session, showed the sharpest fall in the layer of the brain that does most of its processing. Christian Schmitz of the Central Institute of Mental Health in Mannheim led the work.

Tech news in one quick read: Get the most interesting stories in startups, tech and programming, each with a short TLDR, in one daily email from TLDR.

Subscribe to TLDR →

We may earn a commission if you sign up.

Most participants described a strong altered state, with feelings of boundlessness and a loosening of the sense of self. Their experience looked a lot like a psychedelic one, though a weaker version of it.

Thirty practitioners, one scanner session, no control group

The volunteers were aged 26 to 64, half of them women, and most had practiced breathwork for one to three years, usually less than monthly. Anyone with a psychiatric or neurological disorder, or who had used psychedelics in the previous three months, was excluded. Earth.com’s account of the study says each participant breathed continuously in the scanner, with music playing, for between 36 and 96 minutes, rating the intensity of the experience every 12 minutes against their strongest past session.

Medical staff supervised throughout, and monitoring continued for at least an hour afterward.

Resting-state brain network scans were taken before and after the session, not during it. The design had no comparison group, so there is no way to separate the effect of the breathing from the effect of lying in a scanner listening to music for more than an hour. The researchers acknowledge that gap openly in their own description of the work.

Carbon dioxide loss and the narrowing of brain vessels

The explanation for the fall in blood flow is chemical. Fast, prolonged breathing blows off carbon dioxide, and a lower level of that gas makes the vessels supplying the brain constrict. In the Mannheim data, flow in grey matter fell from about 30 to about 16 mL per 100 grams of tissue per minute at the peak, which works out to roughly 45%. News-Medical’s report on the findings, which were presented at the ECNP Congress in Munich on Oct. 11, gives different absolute values but the same roughly 45% average drop.

Earlier research had tied drops of 50 to 60% to signs of insufficient oxygen in the brain, and the average here approached that range without crossing it. A 2025 study of similar breathwork measured a 41.6% fall, and the Mannheim authors say the two results agree. Carbon dioxide in the exhaled breath was not measured in this study, which leaves the mechanism inferred rather than demonstrated.

An altered state that tracked network changes, not blood flow

The average peak rating was 3.5 out of 4, and the most common answer was the top score. Questionnaires pointed mainly to a sense of boundlessness and reduced alertness, with milder visual effects. Scores were lower than the ones typically reported after a moderate-to-high dose of LSD or psilocybin, according to the paper in Progress in Neuro-Psychopharmacology and Biological Psychiatry.

How large the blood-flow drop was did not predict how intense a person found the session. The authors suggest a threshold effect may be at work, in which blood flow has to fall past a certain level for the experience to begin and then stops mattering. Default mode network connectivity, a set of regions tied to self-related thinking, showed no overall change at rest. People whose connections weakened the most did report more intense experiences, but that link appeared under one data-cleaning method and not another, so it is tentative.

The reading the Mannheim team draws is that the altered state may come from changes in how brain regions communicate rather than from reduced supply alone. ScienceAlert has separately covered experimental evidence that breathwork can induce altered states. Schmitz said many people who practice intensive breathwork report profound changes in perception and self-experience, and that the experiences appear linked to more than the marked changes in cerebral blood flow.

What outside experts and the authors caution

Hana Adolphi, the study’s co-coordinator at the institute, described breathwork as a legal, inexpensive and non-pharmacological intervention, and said larger studies are needed to determine whether the brain changes have clinical relevance. She also said the study was relatively small and its findings preliminary. Guy Fincham of Brighton and Sussex Medical School noted that the study was uncontrolled and drew only on experienced practitioners.

David Nutt of Imperial College London framed breathwork as a non-pharmacological bridge to research on psychedelics, a view echoed in PsyPost’s write-up. Because the network scans came after breathing stopped, brief changes during the session may have been missed.

The open question is whether the same effects appear in people new to breathwork, and whether a roughly 45% fall in grey-matter flow carries any risk in people with undiagnosed vascular problems. Larger randomized studies with beginners would be needed to answer either.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

Tech news in one quick read: Subscribe to TLDR →

We may earn a commission if you sign up.