Emotional responses are generated in the limbic system, he said, and many people with a troubling disease often become conditioned into being "hyper-responsive" to their environment, which often involves high levels of cortisol.
"They interpret everything as a stressor," he said. "Yoga, on the other hand, engenders the relaxation response, and has the opposite effect on the limbic system."
But some researchers question whether yoga's benefits come from the fact that it is also exercise -- something that is "clearly beneficial" in most diseases, particularly cancer, Gansler said.
A 2008 study in Cancer Epidemiology, Biomarkers & Prevention found that women who exercised after receiving a breast cancer diagnosis had both reduced overall mortality and mortality from breast cancer, compared with those who didn't exercise.
Another study, published in the Journal of Clinical Oncology, found that exercise reduced the risk of cancer recurrence and mortality among survivors of late-stage colon cancer.
Whether the benefits of yoga come from exercise or relaxation "is a question that hasn't been addressed in studies," Gansler said.
Few medical organizations have developed any kind of policy statement or guidelines as to whether physicians should recommend yoga to their patients. Most of their members seem neither to condone nor condemn the practice.
Sarita Dubey, MD, an American Society of Clinical Oncology official and oncologist at the University of California San Francisco, said she believes yoga "does support patients mentally and physically while they endure the challenges from their cancer and cancer treatments."
But Moadel said she doesn't see much support for yoga in the medical community just yet.
"I think there's a lack of understanding about it," she said. "They may worry that patients think it's an alternative medicine versus a complementary modality."
Few of her patients are referred to Montefiore's program by physicians. Most find it through word of mouth or advertising.
"I would like to educate them more about how it's helping patients," she added.
Khalsa said negative perceptions among medical professionals may change as the "next generation" of researchers appear to embrace yoga. The fact that yoga research has been published in top journals such as Cancer and the Journal of Clinical Oncology may be proof of that.
Gansler said most physicians realize that a treatment with no harmful effects and a decent cost-benefit ratio "just makes sense."
"The cost is minimal, if anything," he said. "And there's minimal danger, unless you really overexert yourself.
"Yes, the evidence is imperfect," Gansler added. "But it's still very promising that it has a good impact on quality of life and control of some symptoms."
Although the call for more research has been sounded, Khalsa said it may be a challenge because there isn't much funding for yoga studies.
In order for yoga to gain more credibility in the medical community, the literature needs to grow, he said.
"Research on yoga for therapeutic benefits really is in its infancy, and to look at how many studies are ongoing and being published, the temptation is to think that's a reflection of how good yoga is," he said. "And it may not be. We certainly need more research."