Although there is some evidence that yoga may offer medical benefits, in general, this evidence is not strong. There are several reasons for this (including funding obstacles), but one is fundamental: Even with the best of intentions, it is difficult to properly ascertain the effectiveness of an exercise therapy like yoga.
Only one form of study can truly prove that a treatment is effective: the
double-blind, placebo-controlled trial.
However, it isn’t possible to fit yoga into a study design of this type. While it might be possible to design a placebo form of yoga, it would be quite difficult to keep participants and researchers in the dark regarding who is practicing real yoga and who is practicing fake yoga!
Some compromise with the highest research standards is, therefore, inevitable. Unfortunately, the compromise used in most studies is less than optimal. In these trials, yoga has been compared to no treatment. The problem with such studies is that a treatment—any treatment—frequently appears to better than no treatment, due to a host of factors. (See
Why Does This Database Rely on Double-blind Studies?
for more information.) It would be better to compare yoga to generic forms of exercise, such as daily walking, but thus far this method has not seen much use.
Given these caveats, the following is a summary of what science has found out about the possible medical benefits of yoga.
Possible Benefits of Hatha Yoga
, has been advocated as a means of increasing strength, balance, and physical function in seniors. However, there is as yet little scientific proof that yoga offers such benefits or that it is superior to generic exercises such as walking.
There is little doubt that yoga, like any form of stretching, will increase flexibility if it is practiced consistently and over a long period of time.
Hatha yoga is also said to relieve
tension and stress
In one study of 65 women with depression and/or anxiety, a 2-month yoga program specifically designed to address these emotional conditions significantly reduced anxiety (but not depression) compared to enrolled woman who were waiting for the program to begin.
Another study found that participation in a 6-week yoga program was associated with reduced anxiety, depression, and stress in women having radiotherapy for breast cancer.
Adding to this evidence, 32 women who had undergone breast cancer surgery were randomized to receive just physical therapy or physical therapy plus a yoga program (called Yoga in Daily Life).
At the end of the 3-week trial, the women in the yoga program reported less psychological distress. A trial of 122 healthy pregnant women demonstrated that daily yoga practice incorporating deep relaxation significantly reduced self-perceived stress scores compared to standard prenatal exercises.
And lastly, a large 2012 review of 35 studies involving 1,794 people found evidence to support the use of yoga to decrease stress and anxiety, although the overall quality of these studies was poor.
Weak evidence hints that hatha yoga may offer modest benefits for people with
chronic obstructive pulmonary disease
For example, in one controlled study, 59 people with mild asthma were randomly assigned to practice yoga and attend a general class or simply to attend the general class.
The results showed slight improvements in asthma in the treated group compared to the untreated group. However, even these modest benefits did not last; assessment two months later showed no difference between the groups. Furthermore, as noted above, studies in which the participants in the control group do not receive placebo treatment are inherently unreliable.
A small 2009 study of 29 adults with
COPD suggests that a 12-week yoga program may be associated with slight improvement in timed walking distance and self-reported functional ability in these patients.
A special breathing technique called yogic-style Buteyko breathing may reduce medication use and subjective symptoms, though it does not appear to actually improve lung function.
Yoga has been evalulated for its beneficial effects in a variety of chronically painful conditions, such as
low back pain
In one study, 42 people with
carpal tunnel syndrome
were randomly assigned to receive either yoga or a wrist splint for a period of 8 weeks.
The results indicated that use of yoga was more effective than the wrist splint. However, participants in the control group were simply offered the wrist splint and given the choice of using it or not; it would have been preferable for them to have received a more believable placebo, like other forms of meditative exercise.
In a small trial involving 53 women with
, those that participated in an 8-week yoga program experienced an improvement in their symptoms, including fatigue, pain, stiffness, and tenderness.
In a review of 16 studies, researchers investigated the potential benefits of yoga in improving pain and pain-related disability in a range of conditions, including headache, back pain,
irritable bowel syndrome
, dialysis, muscle pain,
carpal tunnel syndrome
All of the studies (12 of which were randomized trials) found positive evidence to support the use of yoga.
Yoga had positive effect on chronic low back pain in a randomized trial of 80 patients. Patients randomized to treatment with a yoga program showed improvement in pain, depression, and anxiety symptoms compared to patients in physical therapy. The program was carried out in a residential setting over seven days and included technique, counseling, and educational lectures.
In a randomized, controlled trial, 8 weeks of daily supervised yoga was modestly more effective than a similar amount of supervised physical exercise in relieving
(eg, hot flashes), decreasing psychological stress, and improving cognitive abilities among 120 perimenopausal women.
Fatigue is a common side effect of
. In one small trial, 31 women who were still experiencing fatigue 6 months after breast cancer treatment were randomized to yoga intervention or health education.
On average, those in the yoga group reported feeling less fatigue.
At least one study supports yoga's usefulness for
congestive heart failure
A small trial involving 54 adolescents with
found that adding 8 weeks of yoga twice weekly to standard therapy was associated with improved eating disorder-related thoughts and behaviors.
Yoga has also been studied for
. In one small trial, patients who supplemented their regular treatment with a yoga program lasting 4 months
had improved symptoms, were able to function better, and reported a better quality of life compared to those who did physical therapy.
To date, only weak evidence has been reported regarding the possible usefulness of yoga for
Hatha yoga has also been promoted as a treatment for
(seizure disorder), but a review of all published scientific trials concluded that there is as yet no meaningful evidence that it is effective.
A review of 11 randomized trials of 800 people with moderate to high risk of cardiovascular disease found some potential benefits for yoga. Yoga for a minimum of 3 months was successful in lowering diastolic blood pressure, triglycerides, and raising high density lipoproteins (the good cholesterol) when compared to little or no intervention. However, the trials were small and of low quality, making it difficult to draw absolute conclusions about yoga's effects on blood pressure and cholesterol or how it translates to overall heart health.
Another review analyzed the benefits of yoga when combined with conventional
treatment in 120 studies with 6,693 people. In the 48 randomized trials, specific yoga techniques were associated with significant blood pressure decreases. The studies suggest a correlation between yoga and lower blood pressure, but the study populations were extremely variable, making it difficult to draw specific conclusions.
Some evidence suggests that hatha yoga is