 Yoga, as practiced by millions of Americans, is often recommended as therapy for a variety of medical conditions, but does it work, and for what? My last video, I talked about how yoga practitioners tend to report better health status, but they also tend to be wealthier, and confounding factors like that make it hard to draw claims about yoga efficacy. For example, when population studies have taken factors like education or income into account, the yoga effects often evaporate. You can't really tell if something is good or bad until you put it to the test. Unfortunately, only about a quarter of the published studies examining the effects of yoga on health or well-being outcomes were randomized controlled trials, and of those, half compared yoga to basically just doing nothing. In that case, if you find benefit, you don't know if it's the yoga itself or whether any kind of exercise would have achieved the same or even better effect. Now look, any kind of physical activity is good, but is there more to yoga than exercise? For example, any kind of exercise, whether low intensity such as yoga or high intensity such as aerobics, may help with menstrual pain compared to not doing anything. In studies on alcoholics, aerobic exercise alleviated depression and anxiety symptoms more than yoga, presumably just because of the greater exercise intensity. Typical yoga is probably best described as a light intensity physical activity. For example, here's the metabolic equivalence of some typical yoga poses. The average may be 2 or 3. Compare that to walking at a typical speed, which is about 3. So in general, walking burns about as many calories as yoga, and brisk walking would burn even more. There's all sorts of crazy claims about how so-called hot yoga expands up to like 1,000 calories, but no, you burn about the same calories at room temperature, so 90 minutes would just be more like 300 calories. But isn't yoga so much more than just a workout? Let's see how the data pans out. Multiple sclerosis, for example. We know that exercise can be beneficial in many health conditions, including neurological disorders, and it may not be surprising that yoga, which involves a series of poses, postures, movements, and breathing patterns that could improve balance, muscle strength, and flexibility, should be found beneficial to patients with, say, multiple sclerosis. Let's see if that's actually true. No benefit for overall quality of life, or physical quality of life, or psychological quality of life. Also, no benefit for sexual function or cognitive function, and this was all comparing yoga to doing nothing. A similar failure to find much improvement in quality of life for people living with chronic diseases in general was noted with only one in seven trials, finding a clinically significant benefit. Researchers did find yoga helped fatigue in patients with MS, but not any better than regular exercise. Same with chronic low back pain. Yoga might decrease pain and improve function compared to not really doing anything, but have the same effect on pain and disability as any other exercise or physical therapy. So if you like yoga and want to make that your exercise of choice, great, but it doesn't appear to have any unique benefits for back pain. Same with insomnia. Yoga works compared to nothing, but not to physically active controls. And for cancer patients, mostly breast cancer patients, walking was found to be more effective than yoga and improving sleep. For markers of systemic inflammation in breast cancer survivors, six months of yoga had a similar effect as six months of non-yoga exercise. Same with cancer-related fatigue and quality of life for women with breast cancer, better than nothing, but no better than other types of physical activity. Finally, for breast cancer survivors, the effectiveness of yoga interventions in breast cancer-related lymphedema, an abnormal accumulation of fluid for which there's no effective treatment, and adding yoga does not seem to help. There are some conditions for which yoga really does appear to pull ahead of the pack, though. For example, chronic nonspecific neck pain. Based on 10 randomized control trials, not only was yoga better for neck pains than control groups in general, which included doing nothing, yoga also seemed to beat out active controls of other types of exercises. The authors tentatively conclude that yoga can relieve neck pain intensity, improve pain-related disability, increase range of motion, improve quality of life, and boost mood among neck pain sufferers.