It would be nice to see the effects of yoga on health borne out by science, and so far the results are encouraging. However, the research is rudimentary so far.
Most studies are short term with few subjects, usually beginners, and every yoga and meditation practice that is tested is different, and may be different than the one you or I practice. The subjects are generally self-selected, so right there it is difficult to rule out other causation for the effects. There is no way to generalize the effects of yoga.
This topic is of particular interest to me as I work with a special population: children and adults with special needs such as autism spectrum disorder (ASD). It would be great if I could point to studies that show that yoga reduces challenging behaviors in people with autism, such as obsessions, repetitive behavior, hand flapping, rocking, routines, self-injury, aggressive behavior, etc. I would love to have scientifically validated evidence that yoga has improved their digestion, another common issue for people with ASD.
Unfortunately, each case has so many aspects that cannot be factored out: medication, dietary changes, school and travel routines, behavioral, music, occupational and physical therapies they may be receiving, etc. In addition, many people with ASD have medical or physical involvement such as cerebral palsy, GI tubes, colostomy bags, allergies, etc. The cases I work with are often non-verbal, have delayed reactions to instructions or have difficulty following verbal or physical cues, such as imitation. Some cannot be taught how to consciously control their breath, even blowing out a candle.
What I can tell the parents and caregivers of the clients is that studies show that yoga helps the general population with reducing stress, physical benefits such as improving respiration, digestion, circulation, muscle tone, balance, coordination, body awareness, flexibility, etc. If it helps the average person, of course it helps people with ASD.
For people with ASD, stress is a certainty: imagine not being able to understand and not being understood, having sensory overwhelm, having medical apparatus that cannot be explained, of not being able to explain or communicate pain and discomfort, likes and dislikes clearly. When I am able to help a client be quiet and still in savasana for 6-12 minutes at the end of a session, it is a big deal to the parents and it is sometimes the only respite the clients have where their minds are not racing and their senses are not overloaded and their bodies are not constantly and involuntarily moving.
But I can’t determine if the effects are long lasting, or if they can try savasana on their own when I am not around. They can’t tell me “what’s happening now” in the present moment. More to the point, I cannot do anything mentalist with these clients, which would seem to be the basis for the eight limbs of yoga. They cannot practice meditation, sometimes limited pranayama, no yamas and niyamas, no chanting, no surrender to God. All they have is tapas: asana practice with me.
And yet, even though as far as I know, they cannot “focus on their breath” or “set an intention” for their practice, or engage in “witness consciousness” I believe they are getting something from yoga. In a mystical way, I believe I am connecting with them through prana and lovingkindness and giving them perhaps their only “religious” experience — an opportunity to connect with their higher selves, with spirit, whether they know it or not. I will never have evidence for this.
The only questions worth answering for me are, does doing a yoga session change my state of being? Does teaching a yoga class change the state of being for my students? Do I and they wish to do yoga the next time it is scheduled? Those are questions that I can clearly see answered with both general and special populations.