Methods
Eligible research participants are randomized into a yoga group or walking group. For 12 weeks, participants complete yoga or walking sessions twice per week with weekly at-home practice. During the study, we collect several types of data to understand how yoga and walking affect mood.
A key component of the research is self-reported surveys. Participants complete surveys at following times during the study: at the beginning of the study; at weeks 4, 8 and 12; and at the final appointment. Survey responses help to determine if mood and feelings change over the course of the study. We also examine physiological data, specifically heart rate variability, and levels of a chemical in the brain called gamma-aminobutyric acid.
Heart rate variability is measured during a YMCA Step Test. Study participants perform the YMCA Step Test at the same appointments as the surveys: at the beginning of the study; at weeks 4, 8 and 12; and at the final visit. We are interested in heart rate variability because it is a marker of parasympathetic nervous system (PNS) activity. Decreased PNS activity is associated with negative emotions. Some types of exercise can stimulate the PNS. By examining heart rate variability patterns after completing yoga or walking, we are looking to see if these activities stimulate the PNS. PNS stimulation could be one way that yoga and walking help treat the symptoms of depression.
We use magnetic resonance spectroscopy (MRS) brain imaging scans to measure levels of a chemical in the brain called gamma-aminobutyric acid (GABA). Scans are performed at McLean Hospital in Belmont, MA. There are two appointments for MRS scans, one at the beginning of the study and one at the end, to understand how GABA levels change in response to exercise.
GABA levels are known to be low in people with depression. Taking anti-depressant medications can increase GABA levels, and decrease the symptoms of depression. Our group has demonstrated that GABA levels in a region of the brain called the thalamus rise after some types of exercise. Increased GABA levels may contribute to improved mood after exercising.
By examining changes in mood, heart rate variability and brain GABA levels, we hope to better understand how yoga and walking work on the body and mind to alter depressive symptoms.