Recently, the founder of Bikram yoga was in the news for alleged sexual assaults which he has denied.

Other than the possibility of a unwated sexual advances by one’s yoga instructor (a risk which seems to be small), it appears to be generally safe to learn yoga. Or is it?

A PubMed (a popular search engine used by the medical community for scientific literature) search (performed today, 6 April 2015) for the terms “yoga” and “adverse events” yielded just one review article entitled ‘Adverse events associated with yoga: a systematic review of published case reports and case series‘, authored by Cramer H, Krucoff C, and Dobos G.

The authors searched the medical literature for adverse events associated with yoga, and reported that, between 1969 to 2012 (the authors published their scientific paper in 2013), there appears to be just 76 unique cases of adverse events associated with yoga.

Of the 76 cases, 66 [86.8%] had no preconditions that were associated with the adverse events while 9 case reports described an aggravation of existing preconditions (e.g. glaucoma, osteopenia, asthma).

The yoga practice that was most often associated with reported adverse events was Pranayama or yoga breathing with 4 reported cases, followed by Hatha yoga (an umbrella term for physical yoga practices) and Bikram yoga with 3 cases each. Siddha yoga meditation and Vinyasa yoga (a yoga practice that involves flowing sequences of yoga postures synchronized to the breath) were practiced in 2 and 1 cases, respectively. The other case reports or case series did not report the specific yoga practice.

Regarding specific yoga postures, the headstand (Sirsasana) was practiced in 10 cases [13.2%], the shoulder stand in 3 cases [3.9%], variations of the lotus position (Padmasana) in 3 cases, forceful breathing techniques in 3 cases, voluntary vomiting (Kunjal Kriya) in 2 cases, and postures that included putting 1 or 2 feet behind the head in 2 cases. Kneeling posture (Vajrasana), locust pose (Salabhasana), bridge pose (Setu bandha), seated forward bend (Paschimottasana), and downward-facing dog (Adho mukha savasana) were practiced in 1 case each.

Among the adverse events reported, twenty-seven (35.5%) affected the musculoskeletal system; 14 (18.4%) the nervous system; and 9 (11.8%) the eyes.

Fifteen cases (19.7%) reached full recovery; 9 cases (11.3%) partial recovery; 1 case (1.3%) no recovery; and 1 case (1.3%) died.

The authors concluded from their study that, “As any other physical or mental practice, yoga is not without risk. However, given the large number of practitioners worldwide, only relatively few serious adverse events have been reported in healthy individuals. Therefore, there is no need to discourage yoga practice for healthy people.”

One limitation of the study is that there could be gross underreporting of yoga-related adverse events in the medical literature.  This is reflected in the figure shown below (which is available in the paper published by the authors) where one can see substantially more case report/studies in recent years (2004-2012) than in previous ones, and based on this trend, it seems likely that more cases might surface in future.

Indeed, of the 37 reports of yoga-related adverse events in the medical literature, the overwhelming majority (n=19) originated from the USA, as compared to only 5 from India, the country that yoga originates from. As for the remaining reports, 1 came from Canada, 2 from the UK, 1 from Germany , 1 from Switzerland, 2 from Italy, 1 from Denmark,, and 1 each from Nepal, China, Taiwan, South Korea, and Australia.

In summary, while it seems assuring that there has not been a substantial number of yoga-related adverse events reported in the medical literature, this could be due to under-reporting of events, and more studies should be conducted to establish the safety of yoga.