The effect of a hatha yoga practice on factors related to chronic stress

Abstract

This thesis investigated the efficacy of an eight-week randomised waitlist controlled yoga intervention for middle-aged Australian women reporting chronic stress and psychological distress (N = 116). The research included two primary components. The first was a process evaluation of the implementation and quality of a standardised yoga protocol in a chronically stressed female population. The second component involved three outcome evaluation studies conducted to explore the longitudinal effects of yoga practice on psychological mental health variables and physiological variables, including a pilot study that explored biochemical markers of stress (i.e., inflammation proteins and deoxyribonucleic acid [DNA] methylation). Paper 1 reports on a process evaluation that includes discussion regarding the development of an eight week secular yoga intervention and the underpinning theory, evaluation of fidelity and quality of its implementation, and examination of causal mechanisms and contextual factors associated with clinically significant improvement in distress (reported by 43% of women in the yoga intervention). These reported improvements in distress were comparable to psychotherapy, and participation in yoga classes was associated with improved positive and negative affect. It was concluded that yoga intervention was feasible for treatment of distress and was positively received by participants. Paper 2 presents an evaluation of psychophysiological indicators of health following completion of the yoga intervention. Compared to a control group, practicing yoga was found to be associated with increased positive affect, and decreased levels of distress and stress. Additionally, decreased waist circumference and increased flexibility were demonstrated. These findings indicate that an eight-week yoga intervention is associated with psychological and physiological benefits that exceed those attributable to the effects of time. Paper 3 presents results of a longitudinal study that explored mental health variables at baseline, post-test and follow-up (one month) time-points. A strong effect of time was indicated as distress was found to decrease in both the yoga and control group, although positive affect was only benefited in the yoga group. Improvements reported at post-test were not robustly seen at follow-up indicating the benefits did not persist without continued regular yoga practice. Paper 4 reports on a small pilot study (N = 28) that investigated the effect of yoga on biochemical variables associated with stress. Compared with the control group, women in the yoga group exhibited moderately higher levels of serum interleukin-6 (IL-6) and expressed less methylation in the tumor necrosis factor (TNF) region. Mental health variables were found to be moderately associated with C-reactive protein (CRP) and the methylation of IL-6 (region 1), CRP and LINE-1 (global methylation). Although the findings indicated some early methylation changes, the methodological constraints of the study only allow for preliminary insights and need to be further explored using larger samples. In conclusion, this thesis demonstrated that an eight-week secular yoga intervention was associated with some short-term mental health benefits in distressed women and is a feasible treatment option. However, it did not appear that the benefits were robustly maintained beyond engagement with the yoga classes. Some evidence for molecular effects were indicated by tests involving specific biochemical markers of immunity. This thesis provides support for the potential value of larger scale trials examining efficacy of yoga practice in treating stress-related illness.