Bikram Yoga Reduces Depressive Symptoms in Clinical Trial

As yet another bead of sweat dripped from the end of my nose and landed in my lap, I briefly opened my eyes and gasped at my reflection in the mirror. I looked as though I had been caught up in a torrential storm; I was drenched. This was my first experience of a hot yoga class, and boy was it tougher than I’d naively anticipated. Alas, there was little time to pause for contemplation on my soddened appearance before the instructor guided us into our next “asana”, or yoga posture.

When I left the studio and its sweltering heat, it dawned on me that I felt different from when I had arrived. Lighter? Calmer, or a little less weighed down by my seemingly never-ending stream of thoughts? I wasn’t sure, but I knew that whatever “different” was, it felt good. A few days later, I went back to the studio again. And then again, and again.

Now a fully-fledged member of said studio and a qualified yoga teacher, I no longer grimace at the thought of getting sweaty in a confined space with several other strangers. Ironically, the heat of the studio has become a sanctuary of sorts.

As a yoga student and teacher, I have witnessed first-hand the positive effects that a yoga practice can have on an individual. At the same time, as a trained scientist, I have had to navigate my own feelings of scepticism surrounding some of the claimed “benefits” of yoga.

High-quality research in the arena of “how yoga affects the body and brain” is often hard to come by for a whole host of reasons that largely center around the nature of the practice – it is highly subjective. The experience is shaped by the individual, their experience of the teacher, the style or tradition being taught and the setting, among other factors. Crafting a scientific study that robustly measures the impact of yoga – which can be replicated – is far from an easy feat. That’s not to say that scientists aren’t trying their very best to do it.

Investigators at Massachusetts General Hospital recently published the results of a randomized, controlled eight-week trial investigating the effects of Bikram yoga in people with moderate-to-severe depression.

The study, reported in the Journal of Clinical Psychiatry, was led by Dr. Maren Nyer, director of Yoga Studies at the Depression Clinical and Research Program at Massachusetts General Hospital and an assistant professor of psychiatry at Harvard Medical School.

Bikram yoga reduced depressive symptoms by at least 50%

Nyer and colleagues randomly assigned 80 participants, the majority of whom were female, into 2 groups. The first group of 33 participants received 90-minute sessions of Bikram yoga, practiced in a 105 °F room. The second group of 32 participants was assigned to a waitlist, eventually receiving the intervention after the wait period was over. Some participants across the groups were taking antidepressant medications, while others were not. 

The Bikram yoga sessions were held across two studios in Boston by Original Hot Yoga certified teachers. Participants were prescribed two 90-minute sessions per week and could choose which studio they attended. Ultimately, the intervention group completed an average of 10.3 classes over the 8-week study period.

The researchers used the clinician-rated Inventory of Depressive Symptomatology (IDS-CR) scale to measure depressive symptoms, which was administered at baseline and weeks 1, 3, 5 and 8. This was the primary outcome measure, but the team also administered other self-report surveys throughout the study, including but not limited to The Hamilton Depression Rating Scale (HDRS) and The Exercise-Induced Feeling Inventory (EIFI).

After eight weeks, the yoga intervention group showed a significant reduction in depressive symptoms when compared to the waitlist participants. Sixteen of the yoga participants had a ≥50% decrease in symptoms, compared to 6.3% of the waitlist participants. Many of the participants receiving the yoga intervention presented with such low IDS-CR scores that their depression was considered to be in remission. A total of three mild adverse events, including headache, back pain and knee pain were reported in the yoga intervention group across the course of the trial.

In study exit interviews, participants were also asked to rate how much they enjoyed the Bikram yoga on a scale of 1–10, the average score for which was 7.17. The average score for how much they enjoyed the after-effects of the practice was 8.33.

Nyer and colleagues’ study offers new insight into the potential effects of alternative therapies for depression, which currently impacts five percent of the global adult population. Technology Networks recently interviewed Nyer to dive deeper into the study rationale, its findings and limitations.

Molly Campbell (MC): Why do you think it’s important to explore the effects of yoga practices on mental and physical health? 

Maren Nyer (MN): People are using yoga, and the benefits are not fully captured or explored with large-scale rigorous testing that would allow for insurance companies and medical providers to start to view yoga as a real treatment, either adjunctive to other established treatments or as a standalone treatment.

You could explore different pathways for different conditions and types of yoga, but for our purposes, we study depression. The rates of depression have increased 25% since the pandemic. There is a shortage of mental health treaters and the treatments we have do not always work or fully work.

For example, an antidepressant may help someone reduce overwhelm and function well enough to work and get through their day, but they may not feel totally “well” or “vital.” Yoga is exciting in that it offers mind–body benefits that can potentially treat conditions that commonly co-occur. For example, Dr. Robert Saper showed that a certain sequence of yoga is as effective for low back pain as physical therapy. Imagine a person with depression and low back pain, and being able to treat both at the same time?

The other thing about yoga is that, from personal experience, I feel it offers a pathway to experience more optimal states such as joy, appreciation, contentment and vitality. Sometimes our mental health treatments aim to reduce symptoms but do not offer a pathway to achieve the more positive states. 

MC: Why did you choose to study Bikram yoga specifically, given that there are other styles of yoga – such as vinyasa and yin – that are now taught under heated conditions?

MN: I started doing Bikram yoga in graduate school. I had done a standard non-heated yoga and it never clicked, even with good teachers. However, the heat really matched my own intensity and started to reduce my anxiety, stress and worry and improved my concentration, sleep, focus, determination and energy. I wanted to recommend it to my clients at the time, but there was nothing in the literature discussing heated yoga except two case reports that were both reporting negative effects of the practice.

By some stroke of serendipity, I ended up with two amazing mentors, Dr. David Mischoulon and Dr. Maurizio Fava, who were experts in exploring innovative and complementary treatments for depression.

We paired with the local yoga studios, specifically led by Ms. Jill Koontz, a certified instructor and studio owner, and were able to do a small open trial that was the precursor the current NIH/NCCIH-funded study. All yoga sessions were kindly donated from the yoga studios for both studies.

It ended up that my own personal experience with the heat had some backing in science. As we were running this current study, research by Dr. Charles “Chuck” Raison (the last author in this study) was published in JAMA Psychiatry that showed these very large effect sizes for treating major depressive disorder with one session of whole body hyperthermia in temperature ranges similar to Bikram yoga.

MC: Why is it generally challenging to measure the benefits of an intervention such as yoga on human health, whether that’s physical or mental health?

MN: It is very hard to develop a control group to blind the participants. I haven’t figured out a way to blind participants to what condition they are getting, meaning that there are expectancy effects that are difficult to control.

I think yoga on some level is an energetic, emotional, physical, spiritual and mental practice. As such, our primary outcome about depression captures a little sliver of the human experience/the improvements that a yoga practice could make on a human’s physiology, mind, energy, etc.

I think yoga does much more than alleviate symptoms of depression, but we have these models for viewing mental health and/or physical health and have to fit our outcome measures into funding mechanisms and use scientifically rigorous measures. If we want insurance companies to pay for yoga, for example, we have to study conditions that are established and known to cause great burden. So, I think there are confines on how we view mental and physical health in the medical world and then our measurements can be limiting. This doesn’t mean the research we are doing is not important, but it is confined/structured/defined by these forces.

MC: Your study included participants who were both on and off treatment with antidepressants. How did you account for this in your analyses, and did you observe any differences in the effects of Bikram yoga across these participants?

MN: Since this is a new area of study, we wanted to allow for people on stable antidepressant medications who were still meeting our baseline level of depressive symptom severity, and those off of antidepressants.

We did this because it helps with recruitment since entry criteria are more flexible and it allows us to explore populations with different baseline treatments at the same time to see if we can detect differences in how they respond.

We did not find any differences in how these two populations responded to the treatment. Interestingly, Dr. Raison’s whole-body hyperthermia study recruited patients not taking medications, which followed indications from a small open trial he published in the American Journal of Psychiatry where the three people who were taking antidepressants did not respond to the whole-body hyperthermia. We did not see this in our study, but our study combined yoga and heat, which may account for differences in response.

MC: Were the same teachers used for the same participants in each class, or did this vary? And do you think this could impact the primary outcome?

MN: The teachers varied depending on what classes people took. There were a lot of classes offered per week with a variety of teachers, so we did not control for that or even code that in our data. It is an interesting question, we just didn’t look at it in this study.

My hunch is that participants got a good variety of teachers, which may dilute any individual effects from the instructors’ personality or teaching style, etc. The study was conducted at two local studios, both of which had numerous classes per week with a lot of different instructors. I do think the instructor can make a big difference in the experience of the class. That would be a great question to start to capture more data to be able to explore.

MC: The sample of participants in your study included more minority participants than is commonly seen in the yoga literature. Can you talk about this in more detail, and why it is important?

MN: We truly got lucky in that we had a more diverse sample than is normally seen in clinical trials. I wish I could say that we did something special. We did not, apart from including advertising targeted at various segments of the population, which is our usual practice.

My hypothesis is that the non-medication-based study was appealing to more diverse populations who generally may feel distrustful/alienated towards the medical establishment or reluctant about medications in general.

It is so important to get more diverse samples into our research – and that is in all ways – socioeconomically, geographically, racially, etc. If we just have studies of white individuals, we can’t be sure that these results hold for those who are not in that demographic and there are equity and access issues inherent in just studying these populations. Yoga studios are usually in more affluent areas, and as such, there are access issues involved as well. The large-scale data suggest that yoga users in the USA are primarily well-educated white women. We need to make yoga more accessible to more diverse populations, especially marginalized populations. We have written an article that is under review about this issue.

MC: Can you talk about the IDS-CR scale used to measure the primary outcome in this study? Are there any limitations to its use?

MN: Our primary outcome was clinician-administered, which is the gold standard for depression trials. The issue is that we don’t have anything that doesn’t involve a clinical interview at this time to get data on whether someone is depressed.

There are ways to look at, say, vocal tone or data captured from a cell phone or wearable devices that can be associated with depression. At this time that does not replace a clinician-administered interview. There are no definitive biomarkers for depression. We did look at biomarkers in this study such as inflammatory biomarkers, RNA expression, heat shock proteins and salivary cortisol. There are many ways to explore physiological measures associated with depression and the improvement in depression – such as neuroimaging, heart rate variability, inflammatory biomarkers, etc. So, there are a lot of exciting ways to use wearable devices, cell phones and biomarkers to answer interesting questions.

MC: Bikram yoga is renowned for being quite rigorous. Do you think it’s possible that other styles of yoga – when practiced in the heat – could deliver a similar effect? 

MN: I think that would be a great study to do. The issue for me is that I really want to study the heated aspect. I personally need the heat in Bikram yoga to feel the benefits that I seek. That doesn’t mean that is true for everyone.

There is an empirical question as to whether the heat needs to be Bikram level (105 °F) vs. the heat in some of these other heated yoga styles, which I think is usually more in the 90 °F range.

The instruction is also so different in the different styles, meaning there are countless studies to be done to see what works and for whom. At this point, we just don’t know. I always tell people to do what feels good and intuitively right for their body, whether that is heated (at various degrees of heat and/or rigor) or non-heated yoga or something else. The exercise literature tells us that if people do not enjoy what they are doing, they won’t do it. So just make sure whatever you do feels right to you and your body and is feasible.

MC: Are you following up with the participants to measure the impact of the intervention beyond eight weeks?

MN: We gathered one month follow-up data. We haven’t analyzed it yet. It is a little complicated because the “free study yoga” stopped. We did try to gather data on whether people continued yoga and where, and we need to analyze and publish those data. Whether people continue is a really interesting question, as is how long the results last if you stop practicing.

MC: Is there anything that you would like to add?

MN: Remember that if you think you’re depressed, don’t try to self-treat. Get an evaluation from a medical or mental health professional who can make an accurate diagnosis and recommend appropriate treatment approaches.

Dr. Maren Nyer was speaking to Molly Campbell, Senior Science Writer for Technology Networks.

Reference: Nyer M, Hopkins L, Nagaswami M, et al. A randomized controlled trial of community-delivered heated hatha yoga for moderate-to-severe depression. J Clin Psychiatry. 2023. doi: 10.4088/JCP.22m14621