[dumbneurologist]

this is not meaningful work, because there is no "brain health" outcome in the papers they reviewed that is clinically relevant.

For example: "Increase in right hippocampal GM density among yoga group." Why is this a good thing? Let's not even talk about the physical inappropriateness of using "density" to discuss MRI results.

Using meaningless-but-easy measurements as a surrogate / proxy for meaningful-but-hard measurements is an entire field called "biomarkers". It's incredibly challenging in neurology, and we don't have many good, validated biomarkers. If you want to use "MRI density" (sic), or "fMRI activation", then first you need an entire study to prove that the biomarker is valid. This a subtle point, but it's as if you're counting lines of code to determine the best programming language: yes, it's a measure, but how does it relate, and what does it mean?

We all (including doctors) want things that are natural, wholistic, and give us a subjective sense of well-being (like exercise and mindfulness) to be magically effective. But that doesn't change the need for rigorous science in order to know that it's the case.

And the formula is always the same: a double-blind, placebo-controlled trial within a representative population using a directly meaningful outcome.

This review failed the "meaningful outcome" part, even if (and I personally don't care to look further) they got the rest of pieces right.

[jvanderbot]

It's not a total wash:

"The studies reviewed also implicate the role of yoga in functioning of the dlPFC and the amygdala (see Fig. 4). Gothe et al. [24] found that yoga practitioners demonstrated decreased dlPFC activation during the encoding phase of a working memory task in comparison to the controls. Froelinger et al. [30] also found yoga practitioners to be less reactive in the right dlPFC when viewing the negatively valanced images on the affective Stroop task. Task-relevant targets activate the dlPFC, whereas emotional distractors activate the amygdala [49]. Exerting cognitive control over emotional processes leads to increased activation in the dlPFC, with corresponding reciprocal deactivation in the amygdala [50, 51]. The studies suggest that when emotional experience occurred within the context of a demanding task situation, yoga practitioners appeared to resolve emotional interference via recruitment of regions of the cortex that subserve cognitive control. Plausibly, these findings may indicate that yoga practitioners selectively recruit neurocognitive resources to disengage from negative emotional information processing and engage the cognitive demands presented by working memory and inhibitory control tasks demonstrating overall neurocognitive resource efficiency." [discussion, ¶5]

To a literate outsider, this does not seem like hand-wavey bullshit and seems to establish the signal->source->implication chain you request. This just happened to be where I was in the article when I read your comment.

[appleflaxen]

none of these things are directly important. it's hard to recognize, because they sound very advanced and scientific, but it amounts to how bright a spot is on a brain scan. why is brightness there intrinsically good? well... it's not. I know the authors then project the actual measurements into some kind of hand wavy interpretation about how that affects the individual, but it's just hand waving.

no medication would ever be approved by the FDA using these outcomes, nor should they be (unless the community first establishes that it's a biomaker of some kind).

[jvanderbot]

Fair enough. But isnt their statement (and citation) that exerting emotional control directly correlates with measured increases in a particular region ... exactly what we want to see? If all people exerting emotional control exhibit red ears, and yoga practcioners have less red ears when under stressful focused tasks, it does seem reasonable that less emotional control is required. That logic is sound, right?

[dumbneurologist]

On a tangent: how do you know if the outcome is directly meaningful? that part is easy: ask yourself if you, personally, care. If I told you "an hour of Yoga will make your hippocampus more dense on an MRI" you should

1) ignore me, because that isn't even internally consistent

2) ask yourself why that's a good thing.

Compare that to

"your brain scan in 10 years will show less atrophy", or

"your brain scan in 5 years will show less chronic microvascular injury", or

"your scores in attention and daytime sleepiness will improve", or

"your life expectancy will increase by 4 years"

Those are directly meaningful, because you don't need a doctor to tell you why they are good things (or you do because it's jargony, but a doctor could explain it in one sentence)

[ditonal]

I dont think we all want to be things that are natural to be effective. People want pills to be magically effective. Antidepressants fail to outperform placebo once you remove publication bias, there is no first principle scientific basis for them working, yet they are massively prescribed and advocated for and the “chemical imbalance” myth repeated ad nauseum. Meanwhile, meditation and yoga get massively more skepticism because they’re not pills.

The biggest mistake of our current mental health zeitgeist is sharp skepticism of mindfulness and yoga while accepting the magic of pills on pure faith.

[kaitai]

1) Meaningful outcomes are really hard, and research is piecemeal. As a researcher, I know I have to publish intermediate and smaller results, because I can't get grants for bigger studies without a track record of publication. This is the way science is done today. Without an angel to just give $15 million for a study of an idea with no track record, you have to build the justification for longer-term studies paper by paper.

2) Placebo-controlled trials are not appropriate at all times. You can't placebo-control yoga. What's placebo yoga? For acupuncture, they placebo-control by putting needles in random places; for pill studies, you get a pill of indeterminate content. For yoga.... well, you know you're doing it. That may be part of the benefit. No getting around that.