CAM is almost impossible to research. For example, to answer the question 'does yoga work to reduce back pain?' you have to ask what kind of yoga? What kind of back pain? Additionally, what does it mean to "work" — to help someone avoid surgery, hold a job or need less medication?
Some things — the body meridians that acupuncturists say they follow, or energy forces that healers say they manipulate — cannot be measured, and many scientists question their existence.
CAM is not simply a new array of therapeutic tools that need to be evaluated; it presents other ways to think about disease and therapeutics, and consequently new ideas about how research should be strategically developed. Therefore the structure of CAM research should be different, in subtle but important ways.