1. Pain Relief
Among people with chronic low back pain, doing yoga for just 12 weeks led to greater improvements in back function than usual care,  and yoga for 6 months has been linked to significantly less disability, pain, and associated depression. It’s not only back pain that stands to benefit, either.
Yoga has been found to benefit many types of pain, including that from fibromyalgia , arthritis , joint pain , and neck pain .
2. Anxiety and Depression
Yoga may be an alternative to drugs for relieving depression 
Yoga may reduce stress, anxiety, and depression, improve sleep patterns, and enhance overall well-being and quality of life 
A review of yoga as a therapeutic intervention shows it’s an effective form of management for mild anxiety 
Yoga increases the levels of gamma-aminobutyric acid (GABA) in the brain, which may offer natural “anti-depressant” benefits 
And according to the Harvard Mental Health Letter:
"... for many patients dealing with depression, anxiety, or stress, yoga may be a very appealing way to better manage symptoms. Indeed, the scientific study of yoga demonstrates that mental and physical health are not just closely allied, but are essentially equivalent. The evidence is growing that yoga practice is a relatively low-risk, high-yield approach to improving overall health."
3. Increase Flexibility and Balance
As you get older, your flexibility and balance can suffer, increasing your risk of potentially serious falls and fractures. Engaging in yoga is an enjoyable way to enhance muscular strength and body flexibility.
One review of studies involving people in their 60s and 70s found that yoga led to moderate improvements in gait, upper/lower body flexibility, lower body strength, and weight loss, with researchers concluding, "Yoga may engender improvements in some components of fitness in older adults." 
Through improvements in balance, posture, and flexibility, yoga can help keep you nimble and active at any age.
4. Improved Heart Health
Research into the connection between yoga and heart health is still ongoing, but trials that have been done suggest it can benefit heart disease in a number of ways, including:
Reducing high blood pressure
Improving symptoms of heart failure
Easing heart palpitations
Lowering other heart disease risk factors, such as high cholesterol levels, blood sugar and stress hormones
Enhancing cardiac rehabilitation
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12. Harvard HEALTHbeat May 10, 2011