In a randomized controlled clinical trial including adults with moderate to severe depression, an intervention with heated yoga sessions delivered over an 8 week period was associated with clinically significant reductions in depressive symptoms.

Approximately one-third of patients respond to an initial trial of an antidepressant medication.  Switching to a different antidepressant is often successful; however, side effects are common, including weight gain, fatigue and sexual dysfunction, and may contribute to medication discontinuation.  What options are available to the large number of people who do not respond to or do not tolerate traditional antidepressants?  In a study funded by the National Center for Complementary and Integrative Health, Maren Nyer, PhD, Director of Yoga Studies and colleagues for the Depression Clinical and Research Program at Mass General Hospital evaluated the feasibility, acceptability, and efficacy of heated yoga as a treatment for moderate-to-severe depression.

In this 8-week randomized controlled trial (RCT), 80 participants with moderate to severe depression were randomized to heated yoga or a waitlist control.  According to the study’s inclusion criteria, participants on a stable dose of antidepressant (for at least r weeks) could participate. Participants in the yoga group were asked to attend two 90-minute sessions of Bikram yoga practiced in a 105°F room per week.  Depressive symptoms were measured using the Inventory of Depressive Symptomatology — Clinician Rated (IDS-CR).  Waitlist participants completed the yoga intervention after a waiting period of 8 weeks.

• • The analysis included 65 participants (mean age 32.7 ± 11.7 years; 81.5% female): 33 in the yoga group and 32 in the waitlist group. 
  • The mean IDS-CR score at baseline was 36.9 (± 8.8) in the yoga participants and 34.4 (± 6.7) in the waitlist participants. 
  • Participants attended an average of 10.3 (± 7.1) total classes over the course of the 8-week intervention period. 
  • Yoga participants experienced a significantly greater reduction in depressive symptoms measured using IDS-CR scores compared to waitlist participants (P < .001). 
  • More yoga participants (59.3%; n = 16) than waitlist participants (6.3%; n = 2) experienced a 50% of greater decrease in depressive symptoms. 
  • No serious adverse events were reported.

The researchers noted that depressive symptoms were reduced even in participants who received only half of the prescribed number of yoga sessions.  Based on the findings of this study, the researchers concluded that approximately one heated yoga session per week over 8 weeks was associated with a significantly greater reduction in depressive symptoms than a waitlist control. Furthermore, the proportion experiencing a reduction in symptoms was much higher in the yoga group compared to the control group (59.3% vs. 6.3%).  The response rate seen in this study is similar to what is observed in trials of antidepressants; however, the proportion of participants who experienced a reduction in symptoms without specific treatment was much lower than typically seen in placebo-controlled trials of antidepressants. 

Is it the Yoga? Or the Heat? Or Both?

Further studies are needed to determine the specific contributions of each element — heat and yoga — to the clinical effects observed in this study.  There is a growing body of evidence indicating that yoga-based interventions may have positive effects in alleviating depression. Despite the promising potential of yoga as a treatment for depression, the research has yielded mixed results (Nauphal et al, 2019).  In the current study from Nyer’s team, the effect size was large (Cohen d=1.04) for the reduction of depressive symptoms in adults with moderate to severe depressive symptoms. The finding are consistent with a previous study of heated yoga in women with mild-to-moderate depressive symptoms.  

With regard to hyperthermia as an intervention for depression, previous studies have documented that a single session of whole-body hyperthermia may have antidepressant effects.  Researchers hypothesize that thermosensory pathways projecting from the skin to specific subcortical and cortical regions of the brain may affect neural activity.  In humans, heating of the skin to 41°C (or 105.8°F) activates the mid-orbitofrontal cortex, the pregenual anterior cingulate cortex, and the ventral striatum, areas of the brain involved in the regulation of mood and perception of pleasure.  

While we do not yet know exactly how heated yoga exerts its antidepressant effects, this study indicated that heated yoga represents a promising new non-pharmacologic intervention demonstrating feasibility, acceptability, and efficacy.

Other researchers participating in this study included Lindsey B. Hopkins, PhD; Megha Nagaswami, BA; Richard Norton, MA; Chris C. Streeter, MD; Bettina B. Hoeppner, PhD, MS; Chloe E. C. Sorensen, BA; Lisa Uebelacker, PhD; Jill Koontz, MEd; Simmie Foster, MD, PhD; Christina Dording, MD; Naoise Mac Giollabhui, PhD; Albert Yeung, MD, ScD; Lauren B. Fisher, PhD; Cristina Cusin, MD; Felipe A. Jain, MD; Paola Pedrelli, PhD; Grace A. Ding, BA; Ashley E. Mason, PhD; Paolo Cassano, MD, PhD; Darshan H. Mehta, MD, MPH; Christina Sauder, MS; Charles L. Raison, MD; Karen K. Miller, MD; Maurizio Fava, MD; and David Mischoulon, MD, PhD.  

Nauphal M, Mischoulon D, Uebelacker L, Streeter C, Nyer M. Yoga for the treatment of depression: Five questions to move the evidence-base forward. Complement Ther Med. 2019 Oct; 46:153-157. 

Hot yoga potent antidepressant in study (Harvard Gazette)

Hot yoga could help treat depression symptoms, Mass General study finds (CBS News Boston)

Heated yoga may reduce depression symptoms, according to recent clinical trial (Science Daily)