A German study found that yoga was superior to conventional motor training in a small population of children with attention-deficit hyperactivity disorder (ADHD).
An Australian study published in the Journal of Attention Disorders, concluded that yoga "may have merit as a complementary therapy for boys with ADHD already stabilized on medication."
Heather Peck, PhD, a school psychologist at the Bethany Community School in Bethany, Conn., and her colleagues at the University of Connecticut, performed a study last year on children with attention problems -- although not clinically diagnosed with ADHD.
After taking a yoga class in school, the children had improved attention that was comparable to that of their peers who didn't have attention disorders.
"We found significant effect sizes," Peck said. "Their levels of attention came up close to those of the rest of the kids in the class."
Sat Bir Khalsa, PhD, a neuroscientist at Harvard who researches the effects of yoga on sleep disorders, said the therapy promotes focus, which could help explain why it appears to be so effective in children with attention problems.
"What could be better for someone with ADHD than improving their awareness and attention skills?" he asked.
Bray found that it did improve lung function "to some degree," but it had a bigger effect on quality of life.
She said that improvements in posture may have played a role in promoting better breathing and airway function, but the relief of anxiety shook off a tremendous burden of the disease.
"You're surmising that you've changed a mental state," she said, emphasizing this idea is strictly an interpretation.
"No one really knows" what the potential mechanisms of yoga in improving asthma may be, she said. "We need studies to replicate our work."
Harvard's Khalsa agreed with Bray's interpretation.
"Many disorders have a strong stress component, and I think yoga acts on that," he said. It also "increases resilience and stress-coping capabilities" if practiced long enough.
Or it may work -- as in the case of ADHD patients -- by making them more aware of their condition.
"If you're depressed, how can you treat it if you're not aware of it?" he asked. "Yoga ... creates education between your mind and your body that wasn't there before. And education is the first step in any kind of intervention."
He said yoga bears some semblance to cognitive behavioral therapy.
"A lot of stress is due to dysfunctional thinking," he said. "Cognitive behavioral therapy trains you to be aware of those negative thoughts ... and to replace them with more neutral, rational thoughts. Yoga does something similar, but on a deeper level."
Some researchers say yoga may, indeed, have physiological effects.
Dr. Ted Gansler, director of medical content for the American Cancer Society, said some studies have shown evidence of beneficial effects on the immune system. Others still in the works have noted effects on biomarkers including cortisol levels, which play a role in stress, and cytokine production, which plays a role in inflammation.
Khalsa said the associations with decreased cortisol levels make sense, since yoga seems to work primarily by reducing stress.