When I became interested in the Yoga Philosophy of Ancient India, I also became aware of the "New Age" Yoga of the west, people who call themselves full time or part time Yoginis, who set up shop to prey upon people who are gullible enough to believe that Yoga is superior to a wholesome lifestyle change.
Look at this headline from Canada..
Ganja Yoga classes open in Toronto
The study above demonstrated that at 6,12,26 weeks Yoga was no better than conventional stretching to relief back pain or decrease the consciousness of the pain.
The earlier study mentioned did make note of the fact that Mindfulness did add to the relief when it is added to Yoga Practice.
The same was confirmed by the study at York University.