Chronic effects of Hatha yoga on heart rate variability and EEG spectral power in young adults with elevated mental health symptoms

Abstract

More than 50% of adults will be diagnosed with a mental illness or disorder within their lifetime. There is a significant increase in the prevalence of internalizing disorders and associated symptomology (i.e., anxiety, depression, stress) for young adults ages 18 to 35 years compared to other age groups. Despite the increased prevalence of anxiety, depression, and stress symptoms in young adults, there remain significant barriers to mental health treatment. Given these alarming statistics, it is crucial to develop interventions aimed at reducing internalizing symptomology. Yoga is one form of physical activity that represents a non-traditional form of mental health treatment; both acute and chronic bouts of yoga have been shown to reduce mental health symptoms. Acute and chronic bouts of yoga also affect physiological markers including heart rate variability (HRV) and electroencephalography (EEG). However, the available studies in yogic literature are heterogeneous in terms of exercise characteristics (i.e., acute vs. chronic, frequency, intensity, time, types). Moreover, few studies have examined how changes in physiological markers relate to changes in participant-reported behavioral outcomes. Lastly, the methodological quality of the existing literature is poor and there is a need for greater rigor in the study design (e.g., inclusion of true and/or active control groups). Thus, the overarching purpose of this dissertation is to address these knowledge gaps by evaluating the effects of a 10-week (45-minute sessions, 2x/week) Hatha yoga intervention compared to a meditation intervention (active control) and true control group on physiological markers and mental health symptomology in young adults ages 18-35. Results from this dissertation revealed that both 10 weeks of Hatha yoga and meditation led to decreases in self-reported mental health symptoms, with meditation leading to significant reductions in depression, stress, and overall mental health as indicated by the BDI, DASS-21 depression, stress, and total scores. Contrary to the study hypotheses, EEG-derived frontal alpha and theta power significantly decreased over time for all groups, and there were no significant changes in HRV indices. Nevertheless, these results have positive clinical implications for utilizing meditation as alternative or complementary mental health treatment for adults ages 18-35 experiencing elevated mental health symptoms.