**5. Yoga and Immunity Function**

For some time there has been mounting interest in exploring the potential effects of yoga therapy on human immune systems during exposure to stress. In one prominent study assessing the association between exam-taking among students in medical school and their immune system responses, yoga was introduced as a potential mitigating factor. After screening for acute and chronic illnesses, with a sample size of 60 first-year medical students, cohorts were randomly divided equally between a control group and a test group enrolled in a yoga therapy regimen for 12 weeks during the medical examination period (Gopal et al. 2011, p. 26). The yoga curriculum was enforced for at least 35 min daily in the active study group and consisted of yogic prayer for 2 min, *suk¸sma vyayama ¯* (micro exercises) for 6 min, *sthula vy ¯ ayama ¯* (macro exercises) for 4 min, *asanas ¯* (postures) for 12 min, *pra¯n. ay¯ ama ¯* for 4 min, and *dhyana ¯* (meditation) for 5 min. The results of this study positively correlated yoga activity and immune health. The control group experienced a decrease in the levels of interferon gamma (a cytokine that plays an important role in immune response) as well as a significant increase in the serum cortical, heart rate, blood pressure, and respiratory rate. The experimental group did not experience a decrease in the core immunity functions and did not experience an increase in the physiological parameters that mark reduced immune response. The results of the study suggest that yoga helps resist the autonomic changes and impairment of cellular immunity seen in stressful situations (Gopal et al. 2011, p. 26).

A second, more recent study evaluated the effects of yoga on stress, sleep, diurnal cortisol, and malignant cell count on patients with metastatic breast cancer. The screening criteria ensured that the population of women selected for the study had to have at least a high school education and be diagnosed with stage IV breast cancer within 6–24 months. It consisted of a sample size of 91 women randomized into the experimental group with an integrated yoga-based stress reduction program (*n* = 45) and a control group with education and supportive therapy sessions (*n* = 46). The yoga intervention spanned a three month period that consisted of a set of *asanas ¯* (postures practiced with awareness), breathing exercises such as *pra¯n. ay¯ ama ¯* (voluntarily regulated nostril breathing), meditation, and yogic relaxation techniques with visuals, and the yoga intervention focused on attention diversion, awareness, and relaxation as the prominent principles to alleviate stressful experiences. The sessions included ten minutes of lectures and discussions on philosophical concepts of yoga and the importance of these in managing stressful experiences on a daily basis. The sessions were then followed by twenty minutes of warm-up by practicing easy yoga postures, breathing exercises, and yogic relaxation. The final 30 min of the sessions consisted of guided meditation based on awareness by focusing on sounds and chants from Vedic texts as well as touch and sound sensation exercises intended to produce both stimulating and calming therapeutic experiences during the sessions (Rao et al. 2017, p. 253). Participants attended the sessions of the yoga intervention at least two times per week for twelve weeks. The results showed a significant decrease in symptom distress, sleep deprivation, and waking cortisol levels. The primary stress hormone cortisol also significantly decreased compared to the control group (Rao et al. 2017, p. 253).

A third study examining some of the more stress-reducing effects of yoga therapy correlated the function of the endocrine, immune, and nervous systems to stress levels, specifically in environments where human beings experience hormone-level, cytokinelevel, and neurotransmitter-level fluctuations as a result of acute stress, lowering immunity (Venkatesh et al. 2020, p. 9). The authors discovered that salivary human β-defensin 2 (HBD-2) levels increased after subjects engaged in stretching for 90 min in the context of yogic practice, a finding heralded as a breakthrough discovery because HBD-2 is an antimicrobial peptide that is expressed in epithelial cells of the oral cavity and respiratory

tracts, an effect found to be decisive in lowering hormone stress levels measured in all three systems mentioned above (Venkatesh et al. 2020).

Finally, a fourth study of 19 randomized control trials consisted of a meta-analysis and systematic review (sample size of 1300). The study attempted to draw conclusions on the effectiveness of yoga therapy on people diagnosed with HIV. The study looked primarily at the serum CD4 counts, which is a test measuring the presence of white blood cells known as T-cells that are some of the main tools the body uses to fight off bacteria and viruses (Jiang et al. 2021). It found that yoga therapy was functional in significantly elevating CD4 counts (i.e., lymphocyte counts that, dependent on specific serum levels, indicative the effects of HIV have weakened) as well as in reducing stress, depression, and anxiety, while also improving the quality of life for those battling with HIV. These successful results from yoga therapy are apparent immediately post-intervention and long-term follow-up post-intervention (ibid., pp. 505–19). These same debilitating symptoms, stress, depression, and anxiety, are, as we have discussed, at issue when one is suffering from COVID-19.
