The results suggest a significant decrease in psychological morbidity such as anxiety state and trait, depression, treatment-related symptoms and improvement in the quality of life in the yoga group as compared to the controls following surgery. There was also a significantly lower decrease in CD56 % in the yoga group as compared to the controls and lower levels of serum IgA in the yoga group as compared to controls postoperatively. However, there was a significant decrease in CD4, CD8 and CD56 % in the control group alone following surgery. Although studies have shown various stress reduction interventions to modulate serum IgA levels and lymphocyte subsets in individuals, the fact that yoga helped decrease IgA levels postoperatively could be confounded by the
heterogeneity in the extent of disease, type of surgery and disease stage among the groups. This is because earlier studies have shown that the tumor load is directly related to the serum IgA levels in breast cancer patients.[46] On the contrary, it can also be argued that yoga also helped reduce stress and improved anti-tumor immune responses that could have facilitated this change.
Although there is a dearth of literature using yoga

interventions postsurgery, the beneficial effects conferred by similar stress reduction interventions nevertheless support our findings.[25,47] Psychotherapeutic intervention studies have used a number of diverse strategies which have positively affected immune function including hypnosis, relaxation, exercise, classical conditioning, self-disclosure, exposure to a phobic stressor to enhance perceived coping self-efficacy and cognitive-behavioral therapies.[20] A variety of hypnotic-relaxation intervention appear to shorten hospital stays, decrease pain and promote faster recovery following surgery[48] and most are brief, often single sessions and many involve taped suggestions. For example, 241 patients undergoing a stressful medical procedure were randomized to receive peri-operative standard care, structured attention or self- hypnotic relaxation. Self-hypnotic relaxation patients showed decreased pain and anxiety, lower use of self- administered pain medication, shorter procedure times and less hemodynamic instability than the other two groups.[49] These group differences were particularly impressive in view of the brevity of the intervention and the presumed heterogeneity of the patients’ hypnotizable abilities. Another study showed that greater increases in relaxation in response to the intervention were associated with higher NK cell numbers and activity in healthy students taking medical exams.[50] In contrast to the above relatively mild and predictable stress of examinations, breast cancer surgery is a high-stakes stressor with possible consequences that include death, pain, disfigurement, economic losses, alteration in social roles and uncertainty about the outcome.[24] Similar to other studies,[51] patients in our study displayed heightened anxiety prior to surgery and heightened distress persisting in the postoperative period. Studies
have shown that if these stressors are perceived as uncontrollable and unpredictable, they can continue to be associated with elevated stress hormones.[52] Studies in both animal models and humans have shown elevations in plasma levels of epinephrine and cortisol to reflect sympathetic nervous system activation and hypothalamo- pituitary axis activation.[53,54] Coincidentally, such activation is also known to suppress NK cell activity,[15] reduce lymphocyte proliferative responses to mitogens and bring about changes in lymphocyte subpopulations such as NK cell counts.[55] Such immune suppression following
surgery in cancer patients has also been implicated in the promotion of metastasis via numerous mechanisms including the suppression of natural killer cell activity and counts by stress hormones.[16,56] The ability to “unwind” after stressful encounters, i.e., a quicker return to one’s neuroendocrine baseline, influences the total burden that the stressors place on the individual.[57] Earlier studies have advocated that interventions promoting early adaptation can produce substantial benefits for mental and physical health.[53] Our intervention was helpful in reducing postoperative distress and anxiety and also helped improve immune responses in terms of changes in lymphocyte subpopulations such as CD4 and CD8% and NK cell counts postoperatively indicating
that it helped promote adaptation to this stressor. The changes in lymphocyte subpopulations seen with yoga interventions could be attributed to stress reduction
effects and adaptation to the stress of surgery that could have facilitated a decrease in postoperative distress and consequent improvement in immune outcomes.
Catecholamines and glucocorticoids have been shown to rapidly and markedly affect the distribution of NK cells among different immune compartments (e.g., spleen, liver, lungs, circulating blood, marginating pool of blood, etc)[58,59] and it may be hypothesized that changes in these hormone levels could be one of the mechanisms of action of our intervention.
Our study however, has several limitations: i) we assessed only NK cell number and T lymphocyte subsets and not NK cell function or T lymphocyte function, thereby studying the effect of stress on immune cell trafficking rather than immune cell function. ii) We assessed CD4, CD8 and NK cell % by immunohistochemistry as opposed to fluorescence-activated cell sorting (FACS) and this is a major limitation of our study. The tests were run in duplicate by a single observer and quality control was maintained by cross-verifying the NK cell counts with FACS for standardization purposes. Our values of NK cells
in % are similar to earlier findings.[60,61] iii) As patients in this study were those who were enrolled to participate in a trial using yoga and supportive therapy intervention, it will be worthwhile to speculate that cancer patients who seek psychosocial interventions and care are different from those who don’t in terms of psychological distress and immune outcomes.[62] Consequently, meta-analyses has shown that these groups would also benefit more from such interventions,[63] thereby limiting the generalizability of our findings. The stress reduction and immune-enhancing benefits conferred by our intervention could have implications for breast cancer patients who have to endure long-term treatments that could cause more distress and immune suppression.[64] Although studies support the fact that even brief stress reduction interventions can have possible clinical benefits,[22] it remains to be seen if these benefits
can be sustained significantly over a period. Although our study did not show any functional changes in immune responses (lymphocyte proliferation in response to antigens or NK cell activity), it nevertheless supports a trend for the prevention of immune suppression in terms of cell trafficking and counts. However, larger controlled trials with more advanced measures of immune function are needed to study the immediate effects of yoga intervention on surgery outcomes.