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Interesting study.

Yoga and chronic pain have opposite effects on brain gray matter

Chronic pain is known to cause brain anatomy changes and impairments, but yoga can be an important tool for preventing or even reversing the effects of chronic pain on the brain, according to a National Institutes of Health (NIH) official speaking at the American Pain Society's annual meeting.

M. Catherine Bushnell, PhD, scientific director, Division of Intramural Research, National Center for Complementary and Integrative Health, NIH, explained in a plenary session address that many chronic pain patients show associated anxiety and depression as well as deficits in cognitive functions. In addition, brain imaging studies in rats and humans have shown alterations in gray matter volume and white matter integrity in the brain caused by the effects of chronic pain.

"Imaging studies in multiple types of chronic pain patients show their brains differ from healthy control subjects," said Bushnell. "Studies of people with depression show they also have reduced gray matter, and this could contribute to the gray matter changes in pain patients who are depressed. Our research shows that gray matter loss is directly related to the pain when we take depression into account," said Bushnell.

Gray matter is brain tissue with numerous cell bodies and is located in the cerebral cortex and subcortical areas. The impact of gray matter loss depends on where it occurs in brain. Decreased gray matter can lead to memory impairment, emotional problems and decreased cognitive functioning.

Bushnell said there is compelling evidence from studies conducted at NIH/NCCIH and other sites that mind-body techniques, such as yoga and meditation, can counteract the brain anatomy affects of chronic pain. "Practicing yoga has the opposite effect on the brain as does chronic pain," said Bushnell.

She said the studies show yoga practitioners have more gray matter than controls in multiple brain regions, including those involved in pain modulation. "Some gray matter increases in yogis correspond to duration of yoga practice, which suggests there is a causative link between yoga and gray matter increases," Bushnell noted.

Assessing the impact of brain anatomy on pain reduction, Bushnell said gray matter changes in the insula or internal structures of the cerebral cortex are most significant for pain tolerance. "Insula gray matter size correlates with pain tolerance, and increases in insula gray matter can result from ongoing yoga practice," said Bushnell.

"Brain anatomy changes may contribute to mood disorders and other affective and cognitive comorbidities of chronic pain. The encouraging news for people with chronic pain is mind-body practices seem to exert a protective effect on brain gray matter that counteracts the neuroanatomical effects of chronic pain," Bushnell added.


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It's an interesting hypothesis, sadly there have been no randomised trials of yoga, utilising grey matter imaging as an outcome measure, for chronic pain patients, or anyone else for that matter.

The aforementioned study is this one:
Yoga Meditation Practitioners Exhibit Greater Gray Matter Volume and Fewer Reported Cognitive Failures: Results of a Preliminary Voxel-Based Morphometric Analysis

There have been similar hypotheses for Mindfulness, such as the following non-randomised pilot study (and the 6 other non-randomised studies that were reviewed in that paper),
Mindfulness practice leads to increases in regional brain gray matter density. - PubMed - NCBI

In non-randomised trials, there can often be very strong participation biases between cases and controls.

There are lots of reasons for variance of levels of grey matter within populations and merely controlling for age and education should not be considered 'well controlled'.

Socioeconomic status and the cerebellar grey matter volume. Data from a well-characterised population sample. - PubMed - NCBI

I have also seen unexplained drift of grey matter levels in longitudinal studies, making changes difficult to pin on any particular reason, unless the changes have been observed in a randomised control study.

It's definitely worth doing a proper randomised trial of this, but I've seen these sorts of hypotheses fail many times in the past, so I wouldn't hold my breath for a positive result.
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