 Should doctors recommend their patients do yoga? As you've seen in my last videos, the difficulties associated with recommending yoga stem from the low quality of scientific evidence available regarding its effects. Oddly, this lack of evidence is partly due to a common failure among researchers to define what they actually study. They just say yoga without defining what they mean. And different types of yoga differ greatly in what they demand in terms of physical strength, depth of meditation, breathing control, and spiritual component. Yet it's very common for reports of studies not to define which type they used. This not only makes it hard to compare results between studies, it also makes it very hard to translate any findings to the bedside when counseling patients. Yoga is broadly defined as a mind-body practice composed of physical postures, breathing techniques, and meditation. And so if researchers say they put yoga to the test, you'd assume all three components would be present. However, some studies use meditation only and call it yoga, with no postures or breathing. Others only examine breathing exercises and call it yoga. Others consider yoga only postures, and still others say they're studying forms of yoga without any of the three components. And so if a study shows no benefit, does that really mean yoga as commonly practiced didn't help? And if a study does show benefit, what exactly do you tell patients to do to achieve it? We can take some comfort in the fact that a review entitled Is One Yoga Style Better Than Another attempted to compare the effects of the more than 50 different yoga styles used in hundreds of trials, and they concluded that there was no apparent winner in terms of whether the results turned out positive. So to a certain extent they may be interchangeable. I've talked about the need to have active control to see if there's some benefit to yoga beyond just the exercise component, but such controls may still not deal with confounders such as socialization. Yoga usually involves going to classes, so you can imagine if you were studying the effects of yoga on something like depression. I mean, does breaking routine, getting out and meeting other people have any effect independent of the yoga? Sadly for a depression, yoga doesn't even seem to have a benefit compared to doing nothing. Yoga does appear to be helpful with anxiety, but not for people anxious to the extent that they're actually diagnosed with an anxiety disorder. And all the anxiety benefit from yoga appears to just be from the physical activity since there appears to be no benefit compared to other types of exercise. So unfortunately, yoga does not appear to be effective for mood and anxiety disorders. I'll review on the effects of yoga on depressive symptoms in people with mental disorders in general, including conditions like PTSD or schizophrenia, found no significant effect compared to things like social support that offer the same kind of attention or to doing nothing, but did find an effect compared to so-called weight list controls. See, unlike in studies of drug effects where a placebo sugar pill is relatively straightforward, the selection of a control condition is much more complex for behavioral interventions like yoga. And one common solution is a passive control such as a weight list. Basically people are randomized to either yoga or onto a weight list where they'll still get yoga but have to wait a while. Now that's better than having no control group at all since it still controls for the passage of time, meaning whether or not your condition would have just gotten better naturally on its own, but doesn't really control for the placebo effect. If instead you were just told you were entering a study to see if some exercises may help and then unbeknownst to you, randomized to do yoga versus some sort of sham yoga, then you would have the same kind of expectation, either way. But if you know going into it, you're going to get yoga now, which may help, or yoga in six months, and you end up in the weight list control, this may spuriously amplify the difference in treatment effect because people assigned to the weight list may expect to not get better without active treatment. For example, here's a study for yoga on urinary incontinence. Women were randomized to six weeks of yoga or a weight list control group. After six weeks, the incontinence frequency decreased by 70% in the yoga therapy versus only 13% fewer episodes in the control group. But it's possible that the women in the yoga group reported some benefits due to what's called an expectation bias because they expected yoga to be helpful. So based on the body of evidence, one might say there's insufficient good quality evidence to judge whether yoga is useful for women with urinary incontinence. What we'd like to see are studies comparing yoga to time and attention control interventions, some alternative to yoga that entail the same amount of time and attention so people don't even know they're in a control group. Now the question arises, who cares if the benefits from a yoga intervention are due to the placebo effect or expectation bias? A benefit is a benefit. As long as people are getting better, who cares? But it would be nice to know if yoga really helps or not, and here we go. Women with urinary incontinence were randomly assigned to a yoga group or to a rigorous time and attention control group involving nonspecific muscle stretching and strengthening exercises. There are two different types of urinary incontinence. Urgency incontinence, defined as an involuntary loss of urine associated with a sudden strong desire to urinate, or stress incontinence, where an activity such as sneezing triggers an involuntary leak. Three months of yoga didn't seem to significantly help overall incontinence, but it did seem to help with stress incontinence, decreasing by an average of 61% in the yoga group versus only 35% in controls with no significant changes in urgency in incontinence.