[eigenschwarz]

In response to this there is vasoconstriction of the cerebral vasculature. No one knows if mild damage is being done to the brain from this.

Somewhat related (not exact same mechanism, but similar), there is evidence elite free-divers are harming their brains [1]. It is easy enough to find literature about the appearance of SB100 protein with too long apnea training (eg. [2]).

However, breath-holding/apnea is not the same as breathwork. The fact of the matter is, there will be no definitive proof one way or the other until someone directly probes cerebral O2 levels for an acute and chronic intervention of breathwork. Again, as someone who has indeed done psychedelics and meditates, I am open to alternative modalities, but I will personally wait for the science over anecdotes.

[1] https://pubmed.ncbi.nlm.nih.gov/29053942 [2] https://pubmed.ncbi.nlm.nih.gov/19574501/