**3. Intervention of yoga in stress, anxiety and depression**

Yoga as therapy or therapeutic yoga has been defined as application of yoga postures and practice to the treatment of health conditions [34]. Evidence from a growing body of research supports the notion that yoga may bring about positive effects not only in one's physical but also mental health through the downregulation of the hypothalamo–pituitary adrenal (HPA) axis and the sympathetic nervous system (SNS) [35].

#### **3.1 Methodology of yoga intervention**

Since the aim of this review is to look into the impact of yoga specifically on stress, anxiety and depression in this contemporary society, only findings from articles that were published from 2014 to 2021 were reviewed and included. A combination of databases including PubMed, MEDLINE and PsychInfo were used to identify these articles with the help of keywords and phrases such as "intervention of yoga," "anxiety," "stress," and "depression." The search was streamlined to include only studies that were conducted with adults as participants, irrespective of gender or creed. Those that were conducted with children or teenagers below the age of 18 were excluded completely. In addition, studies that included adults suffering from multiple diseases and/or mental health issues, such as psychosis, obsessive – compulsive disorder and health-related aspects of physical fitness were not included in the discussion here. Studies that included pregnant and post-partum participants were also omitted as it is not unusual for this category of participants to undergo depression and anxiety during that period. In terms of the intervention, only studies that integrated classical yoga were included. Hence, the discussion is substantiated with findings from nine studies conducted between 2014 and 2021.

*Intervention of Yoga in Stress, Anxiety and Depression DOI: http://dx.doi.org/10.5772/intechopen.101619*

*CG: control group; CBT: cognitive behavioral therapy; GAD: generalized anxiety disorder; MIG: mindfulness intervention group; RCT: randomized controlled trial; TAU: treatment as usual; and YG: yoga group.*

#### **Table 1.**

*Summary of the intervention and findings of the selected studies.*

The design of all the studies varied considerably from pre-test/post-test to quasi-experimental and randomised controlled trials (RCTs). One of the RCTs was a stratified-randomised controlled with repeated measures [36]. The sample size incorporated in all these studies was relatively small, ranging from 18 [37] to a maximum of 226 [38]. While this review is not limited to qualitative and quantitative studies, the instruments used in each study varied rather significantly. In all these studies, the intervention of yoga was heterogeneous. Studies that had incorporated transcendental meditation or mindfulness meditation (or any other forms of meditation) or pranayama as stand-alone practices are not included in this discussion.

Only studies that assimilated aspects of classical hatha yoga specifically asana, pranayama, prathyahara, dharana and dhyana were included, though the duration of each class and frequency of sessions varied considerably. One study had administered Kundalini yoga; however, it had incorporated all the aspects of classical hatha yoga, hence the findings of that study were included in this review [38]. It is interesting to note that another study had incorporated chanting as part of the intervention [39].

#### **3.2 Outcomes**

On a positive note, most of the studies reviewed (2014–2021), if not all, exhibited appreciable outcomes; intervention of yoga, with or without pharmacotherapy, appeared to be effectual in reducing the symptoms of these mental health disorders [36–44]. A summary of the intervention and findings is provided in **Table 1**. Even though the duration of each and every study reviewed in this chapter varied considerably, that is, from 4 weeks to 6 months, there are implications that the practice of yoga advocates changes in the neural pathways of the human brain, resulting in favorable effects to the brain activity. Evidence has shown that, when compared to controls, there is less activation in the dorsolateral prefrontal cortex of yoga practitioners [45]. It appears that if there is consistency in the practice of yoga, the alpha, beta and theta brainwaves are activated; these have been linked to improvement in not only memory, but also mood and anxiety.

### **4. Discussion**

All the studies reviewed in this chapter incorporated the fundamental limbs of Patanjali yoga, that is, asanas, pranayama, prathyahara, dharana and dhyana. The first two limbs in yoga, that is, yama and niyama, are therapeutic in nature as both entail code of ethics that work at not only intrapersonal (yama), but also interpersonal (niyama) levels [46]. Yama includes practices such as ahimsa (non-violence), satya (non-stealing), asteya (non-lying), brahmacharya (non-excessiveness) and aparigraha (non-greediness). Niyama, on the other hand, encompasses traits such as saucha (cleanliness), santosha (contentment), tapas (sacrifice), swadyaya (selfstudy) and Ishwara pranidana (surrendering to the higher power). It is imperative to note that while none of these studies reported the inclusion of yamas and niyamas as part of the intervention, it is believed that these two limbs may have been interleaved into the yoga sessions in an informal manner [47].

It is common to prompt students in a timely manner specifically during the asana session to practise ahimsa, for example. While mindfully challenging oneself to perform a strenuous or a dynamic pose is encouraged, using unwarranted force recklessly to get into the pose is not. For obvious reasons, just like in any sporting activities, adding excessive pressure at certain joints in the body can and will bring

#### *Intervention of Yoga in Stress, Anxiety and Depression DOI: http://dx.doi.org/10.5772/intechopen.101619*

about unforeseen injury to the practitioner. More importantly, while the pose is being held (being in the pose), students are persistently reminded to bring their awareness to the deep joy and pleasurable feelings that they are experiencing at that moment regardless of whether they are in the full pose or in a modified version. This act of experiencing joy while being in a particular position brings us to one of the niyamas, that is santosha. Hence, in this manner, the other yamas and niyamas are introduced and expounded during a yoga session at the academy where classes are conducted.

In the studies that have been reviewed in this chapter, the instructors assigned to the yoga sessions may have implicitly incorporated the yamas and niyamas but may have inadvertently failed to report the minutiae and hence, the details of the latter were not highlighted in the papers published. Just like in any study, implicit details are imperative for informed choices to be made. If the specifics of the yoga intervention for each study had been reported, it would have been instrumental not only to the researcher and the reader, but also to the participant who may be keen on exploring the philosophical roots of the yogic practice [47].

It is noteworthy that despite the insignificant sample size, heterogeneity in the sample population, varied duration of the intervention and wide-ranging styles of yoga taught, all studies reviewed demonstrated positive results in reducing the scores in depression, anxiety, and also stress.

In one study, where both the yoga group (YG) and the control group (CG) underwent pharmacotherapy during the intervention, the YG not only experienced a significant decrease in ruminations, but also found solace in the practice; participants used yoga as a strategy to help cope with ill-thoughts and other symptoms of depression in daily life [40]. This could be due to the impact of one of the components in the yoga practice, i.e., yoga nidra (guided meditation) that may have enhanced the self-regulatory capacities in the participants. On the hindsight, participants of this study acknowledged that the practice of yoga had intensified their confidence and that the practice had become an internal motivator for continued participation.

Similar results were seen in another study that engaged sudharshan kriya yoga (SKY) [39]. There was hardly any difference in the scores between the two groups (one group did SKY with pharmacotherapy, while the other group did SKY sans pharmacotherapy), purely suggesting that SKY may be effective not only as a stand-alone therapy, but also as an adjunct therapy for patients undergoing medical treatment. This study was exceptional as it had incorporated chanting in the yoga session. Chanting appears to have a healing effect not only on the physical and emotional, but also on the mental and spiritual body. It provides the drifting mind with a focal point. Though the chanting aspect was brief in this study, previous research has revealed that chanting has the potential to bring about deactivation in the amygdala, parahippocampal and hippocampal brain regions [46]. By stimulating the auricular branches of the vagal nerves, chanting creates vibrations at the cellular level. It is these vibrations that create neuro-linguistic effects which induce tranquility in the body and mind. Those suffering from depression tend to have a noisy mind – one that is cluttered with heaps of unnecessary thoughts. It is believed that the sounds of the mantra have the ability to mask the negative voices in the brain. Only when these ruinous thoughts are eradicated, can the mind have room for positive contemplations.

Similarly, the eight-week yoga intervention study which was conducted on 18 patients diagnosed with anxiety in the US showed a significant reduction in depressive symptoms (*p* < 0.05) [37]. However, in the stratified RCT study that engaged college students in the USA, yoga and mindfulness practices were seen to be equally effective in reducing not only depression and anxiety, but also stress, even though

the self-compassion scores were more significant for the mindfulness practice group [36]. The intervention in the study also lasted 8 weeks.

In a study conducted amongst a subsyndromal population in Australia, a six-week yoga intervention was found to be effective in reducing depressive and anxiety symptoms in both groups of participants, the YG and the CG [41]. There was reduction in psychological stress and rumination, an increase in resilience, and an improvement in mental well-being. It is interesting to note that findings of this study revealed that the yoga participants, on their own accord, had reduced medication dosage and frequency of visiting the counsellor. Though the reasons for these actions are indistinct and warrants deeper investigation, the yoga intervention mode appeared effective in managing the issue at hand of these participants. Pharmacological interventions for depression and anxiety usually produce a delay of approximately 4 weeks before exerting significant mood effects over placebo; it may take up to 12 weeks to achieve full anti-depression effects with medication [48]. Hence, time is definitely a parameter for consideration in yoga intervention. However, in this Australian study, it was suggested that a 30 min yoga practice over 5 days per week should suffice for all and sundry.

Similar positive outcomes of practicing yoga were observed in a depressive and withdrawn community who participated in a randomized controlled trial in San Francisco [42]. Unlike other studies, participants in the YG in this study not only asked for more yoga sessions, but also sought permission to attend the theoretical sessions on yoga history that were specifically held for the CG. It appears that these participants were definitely eager to do yoga for the benefit of their own mind-body health, but at the same time, interested in understanding the physiology behind this ancient science. Specific asanas such as dhanurasana (bow pose), ardhakati chakrasana (half waist wheel pose), ardha chakrasana (half wheel pose), Bhujangasana (cobra pose), setu bandhasana (bridge pose), sarvangasana (shoulder stand) and matsyasana (fish pose) employed in this study were found to be effectual in helping the participants manage their depressive moods and anxiety. It is interesting to note that most of these asanas are heart/chest openers. It appears that in the process of expanding the chest and rib cage to oxygenate the lungs efficiently, these asanas have helped in managing symptoms of depression such as grief, anger and frustration.

The findings from an Iranian study which was carried amongst 52 women suffering from some form of mental health disorders albeit free from pharmacotherapy, was equally positive; the intervention of yoga as a stand-alone therapy brought upon a reduction in anxiety, depression and also stress levels (p = 0.001) in the participants who did 12 sessions of yoga over a four-week period [43].

While most studies showed promising outcomes, one study hardly showed any significant statistical difference between the YG and the CG even though there was evidence of a reduction in depressive symptoms and better social functioning in the YG [44]. These positive effects could have been merely an after effect due to the relaxation techniques included in the yogic regime. Relaxation techniques in yoga are known to downplay the sympathetic activity and balance the autonomic nervous system responses.

Finally, in one recent three-arm controlled single blind clinical trial, where participants were randomized over a period of 12 weeks to either the kundalini yoga (KY) or cognitive behavioral therapy (CBT) while the CG was subjected to stress education, it was found that the KY group and the CBT group had shown significant reduction in generalized anxiety disorder symptoms. That said, the findings also revealed that CBT appears to be more effective than yoga, and it was concluded that the former shall remain the first line of treatment for anxiety disorders [38].

However, in most, if not all, of the studies reviewed in this chapter, they were subjected to limitations. For example, a few of the studies were predominantly a female sample [40, 43]. While there is a greater tendency for women to suffer from depression compared to men [49], the sample size in these studies was disproportionately represented. Also, most of the studies were limited by the insignificant sample population and heterogeneity. Due to the absence of controls in certain studies, it was challenging to establish whether the results obtained were due intervention of yoga or another factor. RCTs are known to be intervention research of high standards, but most of the studies reviewed here were challenged due to several reasons. Either the randomization was inappropriate, yoga styles in terms of postures, breathing and meditative techniques were too varied and/or incongruence in teaching methods.

Despite the limitations, it appears that participants who have benefitted from these yoga sessions may now have an extra tool at hand to help them manage stress, anxiety and depression. Since there were no adverse effects reported in any of the studies, yoga appears to be a safe practice.