Research finds that regular yoga practice may curb symptoms of depression and alter important stress-related biomarkers.
Depression impacts 17 million American adults annually, often contributing to severe impairments in physical and social functioning. Women are roughly 2 times more likely to suffer from depressive disorders including major depression and dysthymia. Research published in the Journal of Alternative and Complementary Medicine suggests that a 12-week yoga intervention may help to curb both depressive symptoms, and alter biomarkers associated with stress and poor health.
Heart rate variability (HRV) is a biomarker linked to autonomic nervous system function and physical and psychological wellbeing. Chronic stress and prolonged negative emotional states can cause an imbalance between parasympathetic and sympathetic nervous system function, and reduce HRV. Low HRV has been linked to a number of conditions including depression, anxiety, substance use/abuse, eating disorders, and cardiovascular disease.
The study explored whether regular yoga practice may be associated with reductions in depressive symptoms, perceived stress, and positive changes in HRV.
A total of 26 women (13 intervention and 13 control) between the ages of 18 and 50 years of age were randomly assigned to either 12-weeks of yoga instruction, or a no yoga control group. To be included women needed to have mild to moderate depressive symptoms, have a body mass index of <30kg/m2, a report a sedentary lifestyle and no involvement in yoga practice.
Participants were excluded if they were pregnant, nursing, or had any physical condition with contraindications to exercise. During the study, women were required to not begin taking medication or receive counseling or psychotherapy, and to report any changes in antidepressant use. Data were collected before and after the yoga intervention.
Based on responses on a standardized depression measure (Beck Depression Inventory-II) the majority of women eligible for the study met criteria for mild depression, with 4 women (2 yoga and 2 controls) meeting criteria for major depressive disorder (MDD), a more severe and often chronic form of depression. Most women in the sample also reported co-occurring problems including anxiety, poor sleep, and chronic fatigue.
Yoga classes were led by an experienced instructor, and were offered for 60-minutes, twice per week. Sessions included 5 min of breathing exercises, 40 min of yoga postures, and 10 minutes of meditation and relaxation at the end. Participants were asked to synchronize their breath with movement during each yoga session. No adverse events were reported in the yoga or control groups.
Average yoga group attendance was 81.3% (range 67%-100%). A total of six participants dropped out during the study (3 yoga group and 3 controls). This represents a 23% attrition rate in the intervention and control groups. There were no differences in baseline characteristics between those who discontinued and those who completed assessment.
Yoga May Reduce Symptoms of Depression and Perceived Stress
At the end of the 12-week yoga program, the 10 participants who attended yoga classes reported significantly less acute symptoms of depression, and lower levels of perceived stress than at study onset. Depressive symptoms in the yoga group were significantly lower than symptoms reported by control participants, who demonstrated little change in either dimension.
Significant differences between yoga group members and controls on measures of HRV were also detected. After controlling for age and baseline depression scores, the yoga group showed a significant increase in high frequency HRV and decreases in low frequency HRV unlike the control group that showed little change. Neither group showed differences in heart rate at the conclusion of the study.
An increase in high frequency HRV suggests an increase in parasympathetic influence (relaxation). Reduced low frequency HRV points to a decrease in sympathetic nervous system influence (activation). Prior research suggests that low levels of high frequency HRV and/or high levels of low frequency HRV are linked to physical and psychological illness such as heart disease.
Findings from this study suggest that yoga may not only help to reduce symptoms of depression and lessen perceived stress, but also may serve as a buffer against cardiovascular illness.
Results of this investigation are consistent with emerging evidence that regular yoga practice may modulate HRV by increasing parasympathetic activity and decreasing sympathetic nervous system dominance. This may be due to the fact that breathing exercises may increase autonomic nervous system balance.
It remains unclear whether HRV changes and decreases in symptoms of depression and perceived stress are sustainable, or whether they require consistent, ongoing practice. A recent systematic review and meta-analysis of randomized controlled trials examining the effects of yoga in modulating HRV yielded inconsistent results, suggesting that we have more to learn about why and how yoga practices impact the autonomic nervous system.
Although this study points to yoga as being potentially beneficial for women experiencing depression, findings leave several questions unanswered. First, given the high rate of attrition in the yoga group, are all yoga programs feasible and acceptable for those grappling with depression and related symptoms such as fatigue and poor sleep, or are certain programmatic elements required that make some programs more impactful than others? If so, what are they?
Second, given that social isolation often plays a major role in the onset and maintenance of depression, were the effects shown related specifically to yoga, or may they represent an artifact of receiving social support from other women dealing with low mood?
Lastly, given the small number of women with major depressive disorder included in this study, would yoga interventions be feasible and beneficial for women with more severe forms of depression?
All told, this research points to the need for additional studies that examine how yoga may influence depression and whether alterations of biomarkers such as HRV can be used as an objective, physiological measure of a yoga intervention’s success in reducing depressive symptoms.
Originally published at YogaU Online
Chu, IH, Wu, WL, Lin, IM, Chang, YK, Lin YJ & Yang, PC (2016). Effects of yoga on heart rate variability and depressive symptoms in women: A randomized controlled trial. Journal of Alternative and Complementary Medicine. DOI: 10.1089/acm.2016.0135
Field T. Yoga clinical research review. Complement Ther Clin Pract 2011;17:1–8.