In a word, yes! According to Astin and other researchers from the Harvard Medical School and the California Pacific Medical Center:
Their review of the research finds considerable evidence of efficacy for mind-body therapies in the treatment of coronary artery disease , headaches , insomnia, incontinence, improving postsurgical outcomes, chronic low back pain , and disease and treatment-related symptoms of cancer , as well as moderate evidence of efficacy for mind-body therapies in the areas of hypertension and arthritis .
Many studies show great potential for improved health outcomes. For example:
The best way to find evidence is to search PubMed  for a specific mind-body therapy or practice.
Although mind-body research is constantly evolving, some characteristics of these therapies make them more difficult to study than, say, standard drug treatments. This can influence the attitude of the mainstream medical world towards these therapies. It also raises interesting questions about the nature and reliability of all medical research. For example, mind-body therapies and practices:
Sometimes it is also difficult for researchers to interpret outcomes from mind-body therapy research because:
have probably heard about drug trials where some of the participants
are given a new drug and some are given a placebo - a substance that
looks like the drug, but has no active ingredients. The drug company is
hoping that their drug will show more benefit to patients than the
placebo. While it might seem obvious that the drug would show more
benefit, in some cases (particularly in some cultures), the placebo
effect is so strong that that the difference is slight. What this means
is that the patient's expectation of a desired outcome actually causes it to occur, not the drugs.
Many mind-body therapies deliberately employ this so-called placebo effect to initiate the self-healing capacities of the individual. In this context, the placebo is not an unintended or negative outcome. Rather, it is another example of how the mind (which creates meaning) can impact the body.
In an extensive review of the clinical research, top researchers Walach and Jonas concluded that the placebo effect is real and that healthcare providers should seek to use it to benefit their patients.
to this study on stress and aging, there is much important research on
the mind-body connection. The PDF available on this screen lists key
studies, historical and current on the physiology of the mind-body
connection. (It does not list research on specific mind-body practices.)
Click for PDF listing key studies. 
Astin, J., Shapiro, S., Eisenberg, D., Forys, K. (2003). Mind-Body Medicine: State of the Science, Implications for Practice . The Journal of the American Board of Family Practice, 16, 131-147.
E.S., Blackburn, E.H., Lin, J., Dhabhar, F.S., Adler, N.E., Morrow,
J.D., and Cawthon, R.M. (2004). Accelerated telomere shortening in
response to life stress. Proceedings of the National Academy of Sciences. December 7, 2004: 101(49), 17312-17315.
Kabat-Zinn, J., Lipworth, L., & Burney, R. (1985). The clinical use of mindfulness meditation for the self-regulation of chronic pain. Journal of Behavioral Medicine, 8(2), 163-190.
McCraty, Atkinson, and Lipsenthal (2001). Emotional Self-Regulation Program Enhances Psychological Health and Quality of Life in Patients with Diabetes. HeartMath Research Center, Boulder Creek, Calif.: Institute of HeartMath.
Pelletier, K. (2000). The Best Alternative Medicine. New York: Simon and Schuster.
Walach, H. and Jonas, W. (2004). Placebo Research: The Evidence Base for Harnessing Self-Healing Capacities in Towards Optimal Healing Environments in Health Care. Corona del Mar, Calif.: Samueli Institute.