Traditional yogic systems that involve breathing exercises (Pranayama), yoga postures (Asanas), chants and meditation have been known to reduce physical and mental stress, enhance lung functions, and immunity (Hakked et al., 2017). Mindful meditation for a single day is able to decrease the gene expression of histone deacetylase genes (HDAC 2, 3, and 9) and pro-inflammatory genes (RIPK2 and COX2) in experienced meditators (Kaliman et al., 2014). Interestingly, Yoga practice has shown to decrease the oxidative stress markers and up-regulate the expression of telomerase genes, such as telomerase reverse transcriptase and telomerase RNA, suggesting increased cellular viability and reduced cellular aging (Duraimani et al., 2015). Studies have shown that Yoga therapy/meditation can improve health and well-being of a diseased individual by reducing stress besides boosting the immune response (Thirthalli et al., 2013; Danhauer et al., 2019; Tang et al., 2020; Venkatesh et al., 2020). Mindfulness-based cognitive therapy can significantly reduce stress, depression and anger, when administered in-person, or virtually (Schanche et al., 2020; Kuo et al., 2021; Orosa-Duarte et al., 2021; Strauss et al., 2021). Similar to Yoga, mindfulness-based techniques also have immune modulatory effects (Reich et al., 2017; Andrés-Rodríguez et al., 2019).

Some studies suggest the role of yogic controlled breathing in reducing the stress levels, controlling mood fluctuations such as anxiety and depression, and at the same time improving quality of life by motor co-ordination, cognitive performance, heart rate variability, and more (Bernardi et al., 2000; Sharma et al., 2014; Gonçalves et al., 2016; Erdoğan Yüce and Taşcı, 2020). Systolic and diastolic blood pressure is improved immediately after practicing Pranayama (Pramanik et al., 2009; Bhavanani et al., 2011). It is notable that practicing Yoga, especially breathing techniques, may be beneficial to control anxiety, stress and to some extent modulate immune response. However, validating such technique in a clinical set up is obligatory.

Enhanced anxiety and stress levels were reported worldwide in Coronavirus Disease 2019 (COVID-19) pandemic amongst health care workers (HCWs), quarantined individuals (suspected cases), convalescent individuals and COVID-19 positive cases due to sudden rise in cases and inability to manage COVID-19 with medication available in the early stages of pandemic (Luo et al., 2020; Ornell et al., 2020; Pfefferbaum and North, 2020; Halperin et al., 2021). Psychological stress has been reported to increase during the lockdowns, quarantine periods and after stay-at-home orders (Ozamiz-Etxebarria et al., 2020). Anxiety and stress have also increased among people due to recent vaccination drive; some are anxious while waiting for their first or second vaccine shot while others have doubts on efficacy of vaccines, which are still under trial. Psychological stress is a known factor which is detrimental to immune modulation and stress can diminish the immune response post vaccination (Glaser et al., 1998; Segerstrom and Miller, 2004; Pedersen et al., 2009; Madison et al., 2021). It is widely believed that stress associated with COVID-19 may worsen the severity of infection and may render otherwise healthy individuals susceptible to COVID-19 (Cohen, 2021).

Novel coronavirus disease of 2019, often referred as COVID-19 was declared pandemic in March, 2020 (Cucinotta and Vanelli, 2020). Since the virus was reported, there are 119,220,681confirmed cases of COVID-19, including 2,642,826 deaths worldwide as of 5:13 pm CET, 14 March 2021 (WHO, 2020b). COVID-19 is caused by SARS-CoV-2 (novel coronavirus), which has 82% genome similarity with Severe Acute Respiratory Syndrome (SARS) causing virus, SARS-CoV (Chan et al., 2020). SARS-CoV-2 spreads rapidly than SARS-CoV and replicates actively in upper respiratory tract (Hou et al., 2020; Sungnak et al., 2020; Wölfel et al., 2020; Ziegler et al., 2020).

Pneumocytes in lungs are invaded by SARS-CoV-2 leading to collapse of the air sacs (Zhao et al., 2010). An immune response is induced as macrophages and neutrophils rush to the site, initiating inflammation that lead to pneumonia (Wang et al., 2020; Zeng et al., 2020). Death in severe cases occurs because of pneumonia and acute respiratory distress syndrome, where deposition in alveoli and small blood vessels around alveoli is formed impairing the gaseous exchange (Welty-Wolf et al., 2002; Levi et al., 2003; Moore et al., 2020; Tian et al., 2020). Hence, managing the immune response could be one of the treatment strategies for COVID-19.

Although with low mortality rates, there is accelerating rise in number of deaths because of rapid transmission and various mutated strains of SARS-CoV-2 (Fang et al., 2021; Leung et al., 2021; Ozono et al., 2021), resulting in stress among people. The treatments that are or were practiced for COVID-19 include Hydroxychloroquine, Remdesivir, Lopinavir-Ritonavir combination with or without interferon, Dexamethasone and convalescent plasma therapy (Antinori et al., 2020; Grein et al., 2020; Hung et al., 2020; Okour et al., 2020; Valk et al., 2020). Remdesivir is the only United States Food and Drug Administration (FDA) approved drug, which can be used in combination with Baricitinib for faster recovery (Kalil et al., 2020).

COVID-19 is a public health emergency; hence, FDA has issued Emergency Use Authorization (EUA) to a few vaccines, which are under trial. In December 2020, two vaccines, i.e., Pfizer-BioNTech COVID-19 Vaccine and Moderna COVID-19 Vaccine were granted EUA from FDA. Pfizer-BioNTech COVID-19 Vaccine was the first to receive EUA from WHO followed by Astra Zeneca/Oxford COVID-19 vaccine, manufactured by the Serum Institute of India and SKBio (WHO, 2020a). Two prominent vaccines namely, Astra Zeneca/Oxford COVID-19 under the local name of Covishield and Covaxin, developed by Bharat Biotech, India are being administered in India.

Precautionary measures such as N-95 or regular masks, hand-washing, use of sanitizers and social distancing can be effectively supplemented with vaccination and immune enhancing measures such as a good diet, physical exercises, yogic breathing exercises, and meditative techniques including mindfulness. We hypothesize that Yoga, especially the breathing technique, maybe instrumental in COVID-19 management as an adjunct approach. In this article we have discussed the psychological and physiological improvements achieved by practicing Yoga, including Pranayama, or meditation or both and tried to emphasize its role in COVID-19 management.

Yoga uses the traditional wisdom of using breathing for self regulation. Isha Foundation, established by Sadhguru, a yogi, has developed and propagated the practice of simple yogic breathing practices including Isha kriya or long duration breathing technique, Simha kriya or short duration breathing technique, and Shambhavi Mahamudra Kriya (Table 2). A kriya is a yogic action or an inner technique, like controlling the breath. The most remarkable characteristic feature of these kriyas is that they are easy to learn and practice with simple instructions. They are free and app guided. Isha kriya is recommended to be done on empty stomach. Practicing Isha kriya calms mind and body, reduces stress, anxiety, and depression, energizes body, improves health and it is said to empower an individual in handling unpleasant situation around himself/herself. Recent interest is emerging on the efficacy and understanding the biological/physiological/psychological mechanisms of Isha Kriya. Although more research is required, the available literature points out that there is no side effect of Isha kriya (Narayanan et al., 2020); practicing it regularly, twice a day, is more fruitful for health. Interestingly, mood disturbances can be reduced in HCW by single-time Isha kriya practice shown in a pilot study examining the mood changes before and after practice in stressed HCW from surgical grand rounds and an anesthesia conference (Rangasamy et al., 2019). Isha followers often claim that individuals practicing Isha kriya are less susceptible to common cold and flu. However, it needs to be investigated.

Simha kriya, another kriya developed by Sadhguru, is said to boost the immune system, increase lung capacity, purifies body and the mind. It can even help identify individuals with respiratory problem as they are unable to perform Simha kriya after 4–5 days of regular practice. However, there are yet no direct studies reported in the literature.

Shambhavi Mahamudra Kriya is the most studied among the three kriyas, yet it has not been adequately investigated. It is a combination of Pranayama, yogic postures and meditation, again not prescribed in Yogic literature. A few studies have suggested that increase in the heart rate variability, sympathetic tone and vagal afferents balance is associated with Shambhavi Mahamudra Kriya (Selvaraj et al., 2008; Peterson et al., 2017). Though additional studies are warranted, one of the studies provides enough evidence of the relaxation with decreased stress and increased well-being (Sinha et al., 2013; Peterson et al., 2017). Due to COVID-19 pandemic interest in such techniques has re-emerged especially with regard to the efficacy and understanding the biological/physiological mechanisms of Isha Kriya.

In contrast to above kriyas, Sudarshan kriya (SKY), evolved by Art of Living, is well studied and has shown to reduce stress and improve autonomic nervous system, immunity and well-being (Sharma et al., 2003; Brown and Gerbarg, 2005; Zope and Zope, 2013; Chandra et al., 2017; Mathersul et al., 2019). SKY can improve depression and can be beneficial for Post-traumatic stress disorder (Janakiramaiah et al., 2000; Katzman et al., 2012; Seppälä et al., 2014). SKY is beneficial in maintaining oxygen saturation in the practitioners at extreme high-altitude environment and thus reduces the risk of developing high-altitude related disorders (unpublished data). A recent study has shown reduction in stress, anxiety and depression among HCWs during COVID-19 pandemic after SKY intervention (Divya et al., 2021).

Such modifications based on yogic knowledge, require longitudinal randomized trials in comparison to established techniques for efficient integration (Nagendra et al., 2019; Nagarathna et al., 2019a). These breathing techniques are taught by different Yoga schools in India like Isha foundation, Art of Living and other such schools. The followers of these foundations constitute large numbers, either using these breathing techniques or obtaining training in the same. Therefore, it is easy to recruit a sufficient sample size and test such techniques as compared to the basic Yoga techniques. These kriyas often face barriers as there is an attempt for their application as a health care technique by general population (Mishra et al., 2020a, c).

Practicing Isha Kriya regularly, twice a day, is advocated to be fruitful for health. Isha foundation states that individuals practicing Isha kriya are less susceptible to common cold and flu. Hence, the combination of Isha kriya and Simha kriya are often apprised as important non-pharmacological strategy to manage COVID-19. Researchers recommend breathing techniques in COVID-19 management by boosting the immunological response, strengthening respiratory system and improving the immune response (Feng et al., 2020; Khawam et al., 2020). The combined practice might improve COVID-19 by reducing stress, improving immunity, increasing lung capacity, reducing inflammation, and improving wellbeing. However, no proven stress reduction or immune enhancement by administrating yogic breathing such as Isha kriya has been shown. Unlike SKY, despite reported benefits from Isha kriya practitioners, comprehensive controlled trials haven’t been undertaken.

We have earlier reported that pre-diabetics are more stressed than diabetic patients and a yoga intervention, i.e., Diabetes Yoga Protocol, which include breathing exercises, can slow down, if not halt, the conversion of pre-diabetic condition to diabetics by altering the stress responses (Mishra et al., 2020b). Thus, successful management of the co-morbidities may reduce the risk of COVID-19. The aforementioned simple kriyas are designed by Sadhguru to include effectiveness of modulated breathing in everyday routine and can thus reduce the risk of co-morbidities such as diabetes, hypertension and may be COVID-19. A doctor from United Kingdom suggested simple breathing technique, which is popular online, for getting relief from COVID-19 by encouraging gaseous exchange and oxygenation; this technique does not prevent or cure COVID-19 (Hamzelou, 2020).

As it is often argued among Yoga scholars that Isha kriya and Simha kriya may be useful for COVID-19 patients, a randomized pilot study is imperative to study the role of Isha kriya and Simha kriya with the biological/physiological therapeutic efficacy. In order to further evaluate the efficacy of Isha kriya and Simha kriya in COVID-19 a randomized case-control trial is in progress (Trial registration no. CTRI/2020/10/028195).

The first report of immunosuppressive effect of psychological stress was approximately 50 years ago (Herbert and Cohen, 1993). A meta-analysis of 293 independent studies spanning 30 years has revealed that immunity is affected by acute and chronic stressors (Segerstrom and Miller, 2004). While acute stress suppresses some aspects of adaptive immunity and enhances some parameters of natural immunity, chronic stress suppresses cellular as well as humoral immunity. Brief but significant stressors, ranging from student examination to current COVID-19 pandemic, have potential to suppress the cellular immunity. Loneliness has also been shown to enhance stress and inflammation under acute stress conditions (Jaremka et al., 2013; Ozamiz-Etxebarria et al., 2020). Such observations may be seen in individuals who are quarantined, COVID-19 positive, convalescent or those suffering from loneliness (during lockdown), increasing their risk of suffering from severe COVID-19 infection.

Asthma, the respiratory and common allergic disease of 21st century, is associated with psychological stress, anxiety and sadness and has a bidirectional association with panic (Lehrer et al., 2002; Hasler et al., 2005). Negative emotions such as anger and hostile behavior have negative effect on physiology including decline in lung function (Kubzansky et al., 2006). These can be avoided by Yogic interventions.

Studies have shown that psychological stress can increase risk of diabetes, upper respiratory infection and cancer, and has role in progression of cancer (Cohen et al., 2002; Afrisham et al., 2019). Presence of chronic diseases, especially respiratory disorder together with stress may enhance the degree of COVID-19, which may be further aggravated by presence of obesity. Respiratory function is decreased in obese due to decreased lung volume and accumulation of cytokine producing adipocytes (Mafort et al., 2016). It is to be noted that stress and obesity are interrelated because stress can lead to obesity (overeating response) or vice-versa (van der Valk et al., 2018). Nevertheless, both stress and obesity have adverse effect on respiratory function, which may increase the risk and severity of COVID-19. Yogic breathing is an important tool to improve oxygen saturation (Mason et al., 2013).

Furthermore, psychological stress is associated with enhanced susceptibility for viral infections (Perez et al., 2012). Natural killer cells tend to decrease under stress (Ma et al., 2013), which provides immunity until seroconversion and availability of IgG and IgM antibodies to neutralize SARS-CoV-2 in middle or later stages of COVID-19 (Xiang et al., 2020). Apparently, wound healing is also impaired under stress as indicated by increased expression of genes related to cell cycle arrest, apoptosis, and inflammation in wound site neutrophils (Roy et al., 2005).

Age is another risk factor of COVID-19 as immunity decreases with age (Nicholson, 2016). Hence, it is evident that presence of psychological stress in HCWs, quarantined individuals and COVID-19 positive cases may considerably hamper their ability to withstand COVID-19, both mentally and physically. Thus, Pranayama and other breathing techniques may play a substantial role in managing stress and improve immunity that might be beneficial in managing COVID-19 response, especially when patient is obese or aged and/or has chronic respiratory or other disorders. Moreover, use of mask is also an added challenge to a large number of people who are not able to breathe; thus, such yogic breathing can help.

We hypothesize that simple and controlled breathing techniques, such as Isha kriya or Simha kriya, may have role in managing COVID-19-related stress and immune response, which might be helpful in prevention or treatment as an additional and indirect approach. However, the direct involvement of Isha kriya or Simha kriya in psychological and physiological effects needs to be verified. Of note, standard precautionary measures and available drugs and vaccines are the major contributors in COVID-19 prevention and treatment.

Yoga may be instrumental in managing COVID-19 related stress and regulate immunity and inflammation. However, it is important to note that the key factors to control COVID-19 are prevention of the contagion, by following standard norms such as use of N-95 or regular masks, hand-washing, use of sanitizers and social distancing. Moreover, vaccines are readily available and administered in almost all countries and trials are about to complete thereby the severity of this pandemic might reduce in coming time. However, emergence of new strains of SARS-CoV-2 is of concern, as the presently available vaccines might be unresponsive toward these strains. Yoga practices, which enhance immune system, apparently reduce inflammation and related stress (either associated with infection or loneliness during quarantine), and may aid in management of COVID-19 patients, convalescent cases and HCWs, require validation through randomized clinical trial.

Immunity is adversely affected by increased stress. Psychological stress is often reported among the COVID-19 positive patients and those recovering from it, quarantined individuals and HCWs (Luo et al., 2020; Ornell et al., 2020; Pfefferbaum and North, 2020; Halperin et al., 2021). Therefore, it becomes crucial not only to improve immunity but also to reduce stress. Breathing techniques are known to improve the lung functions, oxygen saturation and improved cardiovascular functions. Liuzijue exercise that includes controlled breathing was able to improve pulmonary function and quality of life in discharged COVID-19 patients (Tang et al., 2021). The best precautionary approach to cope up with COVID-19 is by enhancing immunity and lung functions. However, lack of specific Yoga modules or kriyas precludes extrapolation of controlled trials and their consequent translation. Several ongoing randomized control trials, including our study, aims to investigate the efficacy of various breathing techniques in COVID-19 (Lai et al., 2020; Weiner et al., 2020; Zhang et al., 2020). Figure 1 summarizes the effects of Yogic breathing techniques.

COVID19 outbreak and immediate requirement of precautionary measures and treatment has resulted in exploration of breathing techniques, including those outside the field of yogic texts. This may also act as a tool to manage COVID-19, especially in mild and moderate cases. However, drugs and vaccine are required to efficiently treat COVID-19. Such breathing techniques are easy to access during the lockdown, including the HCWs, the quarantined and COVID-19 positive patients, through digital platforms. The yoga scholars at Post Graduate Institute of Medical Education and Research, Chandigarh, India have spearheaded such a digital interface with educational programs that prompt scientific analysis of mindfulness programs via Facebook page, “Yoga Scholar PGIMER”¹. The Isha kriya breathing technique was discussed by Sadhguru in one such program².

Yogic breathing practice such as Isha kriya and Simha kriya are said to be simple to learn and do not require special training and supervision to execute. The combined practice only takes 15–20 min. Hence, Isha Kriya and Simha kriya must be evaluated for their efficacy through controlled trials.

Publicly available datasets were analyzed in this study. This data can be found here: https://www.neuroscienceresearchlab.org/.

MR wrote the first draft. BS, PA, and AA contributed to conception and design of the review. PM edited and critically reviewed the manuscript. All authors contributed to manuscript revision, read, and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.