Intensive breathing, as used in breathwork practices, significantly reduces cerebral blood flow and alters the interaction between key regions of the brain. This conclusion was reached by researchers at the Central Institute of Mental Health in Germany. The study was published in the journal Progress in Neuropsychopharmacology and Biological Psychiatry.

Hyperventilation—that is, intentionally rapid or deep breathing—is increasingly being used for therapeutic purposes. Practitioners report experiencing states typically associated with psychedelics: altered perception, emotional release, the dissolution of the "self," and a sense of unity. The mechanisms underlying these sensations remain poorly understood.

The experiment involved 30 healthy adults with an average age of 45 who already had experience with intensive breathing. During an MRI scan, they performed a self-guided "circular" breathing technique—continuous breathing with no pauses between inhalation and exhalation.

At peak exertion, blood flow in the brain's gray matter decreased by an average of 45,5% compared to baseline levels, while heart and respiratory rates increased. The authors note that this is below the critical threshold of 50–60%—the point at which oxygen deprivation in the brain has been documented—yet it approaches that threshold and significantly exceeds the reduction typically observed during clinical hyperventilation.

At the group level, no significant changes in the functional connectivity of the default mode network (DMN)—which is disrupted by LSD and psilocybin—were observed. However, participants who reported more pronounced altered states of consciousness showed signs of greater changes within this network. Since this finding depended on the specific data-processing method used, the authors consider it preliminary.

The reduction in blood flow did not correlate with either changes in the DMN or subjective ratings of altered states. On average, participants rated the intensity of their experiences at 3,47 on a four-point scale. In the post-session survey, they generally reported a sense of unity, changes in perception, and a diminished sense of self.

According to researchers, a reduction in blood flow does not, by itself, explain altered states of consciousness, though it may create the physiological conditions for them; meanwhile, a reorganization of the interactions between different brain regions likely plays a more direct role in the depth of these experiences. The authors note the study’s limitations—namely, a small sample size consisting of experienced practitioners and the absence of a control group. Further research is required to confirm these findings.