The researchers responsible for the study disconfirming the claim suggest that earlier studies may have been hampered by a small, self-selected, particularly needy participant base and by the fact that any intervention can succeed at first.
Mindfulness meditation can change the brain but only if it is a lifetime, intense practice:
Tibetan Buddhist monks who have spent most of their lives meditating (tummo meditation), often from childhood, can control their metabolism to some extent by mindfulness. But they would be the first to tell us that it takes many years of dedication and training:
“For decades, claims that meditating Buddhist monks could greatly raise their temperature or slow their metabolism were assumed to be exaggerations that would yield to a scientific explanation.
“The claims did yield to a scientific explanation. The scientific explanation turned out to be that the monks can do exactly that.”
The monks’ skills, since corroborated, include control of brain waves. But again, they spend much or most of their lives meditating. It would be more surprising if that fact had no effect on their brains than if it does.
Thus the takehome point should not be that mindfulness meditation is debunked but that changing lifetime habits of thought and their signatures in the brain is not a matter of an eight-week course. A fundamental shift in orientation and habits over many years is likely required to produce, say, signatures in the brain.
Denyse O’Leary, “Study: Eight-week mindfulness courses do not change the brain” at Mind Matters News (May 22, 2022)
Takehome: Tibetan Buddhist monks who can control their metabolism and brain waves have spent their lives meditating. Brain changes are consistent with that fact.
You may also wish to read: Researchers: Buddhist monks’ bodies decay very slowly at death According to traditional meditation lore, they are in a meditative state (thukdam) until their consciousness is clear; only then does the body begin to decay. Neuroscientist Richard Davidson and colleagues found no evidence of brain activity accompanying the stasis in decay for maybe a week in such monks. (Note: slow decay may be, in part, due to a very ascetic lifestyle.)