Yoga & Depression: a literature analysis

Literature Review: Effectiveness of Yoga on Depression in Adults 

Julia Lemmens, CPT & BS Human Biology

August 2019

Abstract

Background. We conducted a literature review of randomized controlled trials (RCTs) to summarize the literature on the benefits of yoga in adults with depression. 

Methods. We searched PubMed 2000-2019. Two investigators screened abstracts for eligibility (adults with depression, tested yoga, reported depression outcomes ≥ 1 month after treatment initiation). We extracted study characteristics and qualitatively summarized findings for depression for each trial.

Results. We identified eight RCTs that met inclusion criteria with trials lasting 5-18 weeks with yoga and control treatments lasting 5-12 weeks for 2-7 sessions per week. Eight of eight trials tested yoga as an independent therapy; one trial also tested yoga in combination with psychological education and mindfulness practice. Trials examined the effects of regular yoga practice in adults ages 18-60 years with mild to severe depression, versus walking, other exercise, or no intervention controls. Trials included mostly females. All eight RCTs reported positive effects of yoga on depression up to 16 weeks after patient participation in treatment regimen. Losses to follow-up were minimal, when reported. An improvement of depression scores of 1.77 to 17.23 points over control was observed.

Conclusions. We found evidence of regular yoga practice having a consistent effect of reducing depression in the short-term for adults with marginal to severe depression. Future studies with longer-term follow-up and broader patient samples would improve applicability of results.

Introduction

Depression is a common and often distressing mental health condition that results in varying levels of functional impairment in adults worldwide. One in ten adults in the US1,2, and approximately 300 million people worldwide experience depression at some point over their lifetime.3 

Symptoms of depression vary from individual to individual but often include sad or depressed mood, decreased interest or enjoyment, lethargy, and decreased activity that lasts for two weeks or longer.3,4 People with depression may experience symptoms of anxiety as well as other related mood disorders.4 Depression severity ranges from mild to severe. Moderate to severe depression may impair an individual’s ability to function at work, school, or at home, and in the most severe cases, can lead to suicide.3 Recovery from depression is often incomplete and relapses are common.2

Early diagnosis and intervention is important in treatment success. The goals of interventions are symptom relief and improvement in quality of life.5 Interventions for depression vary depending on the severity of the person's condition, but typically include an antidepressant medication and/or other psychological treatments, such as psychotherapy, behavioral activation, cognitive behavioral therapy (CBT), or Transcranial Magnetic Stimulation (TMS); some affected adults require residential treatment.2,3 5 Antidepressant medication type and dosage varies, and medications result in varying levels of relief from depressive symptoms.2 Some adults also undertake complementary and alternative medicine (CAM) therapies. 

Prior research reports beneficial effects of pharmacologic, psychological and cognitive-behavioral therapies for some adults with varying levels of depression.6 Also, research on nonpharmacologic interventions (such as exercise or bright light therapy) and CAM approaches (such as Stress Relaxation techniques, meditation, yoga, and acupuncture) is increasing.5-7 Accessible nondrug approaches that could help affected adults reduce or manage current depressive episodes or prevent or reduce the severity of reoccurrence is a broad therapeutic goal. 

Yoga is a unique type of exercise and one of several common CAM interventions that may be beneficial in reducing or managing depression in adults when utilized alone or in combination with other treatments.2,6,7 

We conducted a literature review to summarize the beneficial effects of yoga on depressive symptoms in adults. Review results will help inform faculty and providers-in-training at our academic and clinical center about the randomized trial evidence for the beneficial effects of yoga in adults with depression.

Methods

Literature Search Strategy

We conducted a PubMed database search to identify peer-reviewed literature on the beneficial effects of yoga for reducing depressive symptoms in adults. Our search strategy included the following terms: yoga, depression, adults. We used search filters to limit our search results to randomized controlled trials (RCTs) published from January 2000 to May 2019 on treatments for adults with varying levels of depression, including major depressive disorder (MDD).

Studies for this literature review were selected based on the PICOTS (Population, Intervention, Comparator, Outcomes, Timing, Setting) framework, and on the study-specific inclusion criteria described in Table 1 below.

Study Selection and Data Extraction

Two investigators reviewed titles and abstracts of the PubMed database search results to identify studies that examined interventions for depression and reported at least one patient-reported outcome regarding depression severity. Citations deemed potentially eligible underwent full text screening. 

We extracted data from included RCTs into an evidence table of study characteristics and results.  Extracted data included the relevant population, intervention, comparator, baseline, and outcomes data on depression severity. Initial data abstraction quality was double-checked. 

Data Synthesis

We summarized the results into evidence tables and qualitatively synthesized evidence for each treatment-outcome combination within specific follow-up periods. Studies were grouped by the duration of the yoga intervention: 8-12 weeks or less than 8 weeks. 

Our primary outcome was patient-reported change from baseline in depression (Table 2). In general, we gave RCTs priority over RCT pilot studies. We report treatment effects using change scores from baseline when reported. Results reporting follows a modified PRISMA checklist.8

Table 1. Study inclusion criteria for The Effects of Yoga on Depression literature review

Category

Criteria for Study Inclusion

PICOTS (Population, Intervention, Comparator, Outcomes, Timing, Setting)

• Population: Included Adults age 18 and older with patient-reported depression including major depressive disorder (MDD). 

• Excluded: Women with perinatal depression, menopausal or postmenopausal depression or PMS-related depression; geriatric depression; depression accompanying any terminal condition; adults with cancer or major concomitant health condition(s) other than depression.

• Interventions: Included Studies that tested the effectiveness of any type of yoga (such as Hatha, Yin, Laughing, etc.), alone or in combination with any other treatment 

• Excluded: We excluded meditation alone.

• Comparators: All other treatment options, alone or in combination

• Outcomes: Studies reported at least one patient-reported measure of depression: 

• Depression severity measure (such as Becks Depression Inventory I(BDI-I or BDI II), Hamilton Depression Rating Scale (HAM-D), Hospital Anxiety and Depression Scale (HADS), Depression Anxiety Stress Scale (DASS). 

• Adverse effects of treatment(s): Discomfort/soreness from physical activity if anything. 

• Timing: Follow up, Up to 6 months

• Setting: Any setting.

Study designs 

• Randomized controlled trials.

Time of publication

• Published from 2000 forward; reference lists from systematic literature reviews.

Language of publication

• We limited included studies to English language publications. 

        Abbreviations: MDD: Major Depressive Disorder; PMS: pre menstrual syndrome; BDI: Beck’s Depression Inventory; HAM-D: Hamilton Depression Rating Scale; HADS: Hospital Anxiety and Depression Scale; DASS: Depression Anxiety Stress Scale. 

Results                     

We identified 310 citations via PubMed published from 2000-2019. Filters limited our results to 121 abstracts. After title and abstract screening, we reviewed 12 full text articles to determine final inclusion. Of the 12 articles 8 were specific to Yoga practice pertaining to depression in adults with diagnosed or self-rated depression. Eight RCTs met PICOT criteria and were included in this review, four of which were pilot studies9-16. Four studies were excluded that focused exclusively on pregnancy or hormonally-related depression in women. 

Table 2 shows characteristics of the included studies. All eligible studies enrolled adults diagnosed with depression. Participant age ranged from 18-60 years. Females comprised 49% to 100% of individual study participants. Studies enrolled 23 to 105 adults (Table 2). Multiple types of yoga were used and intervention duration and intensity varied. Control groups included walking control, no intervention (waitlist control, no yoga, or no treatment as usual), and attention control. 

Depression severity at baseline was assessed via five measures: the Beck Depression Inventory (BDI) or BDI-II, the Hamilton Depression Rating Scale (HAM-D), the Hospital Anxiety & Depression Scale (HADS), or the Depression Anxiety Stress Scales (DASS) (see below). Depression severity at baseline ranged from  a mean of 21 for all studies using BDI & BDI-II (low end of moderate range), 14 or greater for Hamilton (mild or worse), and a mean of 6 for HADS (upper end of normal to mild).

Depression Measures

Five different depression outcome measures were utilized. Two studies reported outcomes using BDI,13,14 three studies reported  BDI-II,16,10,12 one study reported using HAM-D,14 one study reported depression severity using the HADS,11 and one study reported depression using DASS.9 The scoring for each test used in the studies are as follows:

BDI scores from 1-10 are considered normal and common depression, 11-16 is “mild mood disturbance”, 17-20 is “borderline clinical depression”, 21-30 is “moderate depression”, 31-40 is “severe depression”, and over 40 is “extreme depression”.17 

BDI-II Scores include 0-13 as minimal depression, 14-19 as mild depression, 20-28 as moderate depression, and 29-63 as severe depression.18 

HAM-D scores 0-7 as “Normal”, 8-13 as “mild depression”, 14-18 as “moderate depression”, 19-22 as “severe depression”, and 23 and above as “very severe depression”.19 

The HADS rates a score of 0-7 as Normal, 8-10 as “Borderline Abnormal”, and 11-21 as “Abnormal”.20

The DASS rates a score of 0-9 as Normal, 10-13 as Mild, 14-20 as Moderate, 21-27 as severe depression and above 28 as extremely severe.21 

Randomized controlled trials

Compared to any control, five out of eight studies interventions reported a statistically significant reduction in depression rating from baseline with yoga; all eight studies reported a reduction in  depression from baseline with yoga. Six studies tested the effects of yoga over 8-12 weeks9,10,12,13,14,16, and two RCTs tested yoga over 4-7 weeks.11,15 The duration of individual yoga sessions varied. Final outcomes were assessed at the final yoga session in all but one 12-week RCT where depression was also assessed at 16 weeks.13 Compared to controls, yoga interventions lasting for 8 to 12 weeks with sessions 2 to 7 days per week produced a statistically significant decrease in depression. 

Four studies whose interventions lasted for 12 weeks took place 2 to 5 times per week with 45 to 120 minute sessions compared to controls (including treatment as usual, no intervention or walking control.) All studies reported decrease in depression after a yoga intervention of -9.92 on the BDI, -5.82 and -12.92 on the BDI-II, and - 3.36 on the DASS at follow up. Three studies reported a statistically significant within-yoga-group reduction in depression (Table 2).9,10,13,16 

Two studies tested 8 weeks of yoga practiced 2 to 7 times per week lasting 20 to 90 minutes. Both studies reported a statistically significant decrease in depression from baseline with yoga compared to control of -9.47 on the BDI scale)12 and -17.23 on the HAM-D scale14 ( Table 2). 

One 7-week yoga trial lasted 7 weeks with sessions occurring 3 times per week for 50 minutes each compared to the control reported reduction in depression of -6 points on the BDI Scale; no p value was reported.15 (Table 2)

One 5-week yoga intervention (2 times per week for 60 minutes) compared to control (no yoga) reported a decrease in depression of -2.75 on the HADS scale after yoga combined with psychological education for 30 minutes. Decrease in depression after yoga alone was only - 1.77. The p value for the combination intervention (with education) was considered statistically significant whereas the p value for the yoga alone was not statistically significant when compared to control.11 Table 2. 

Discussion .

 We found small but statistically significant beneficial effects of yoga on depression severity that was measured immediately after the yoga interventions concluded. One study which reported depression levels one month post-intervention showed that the effects of yoga had diminished but were still improved over baseline.13 All included studies showed beneficial effects of yoga on depression severity versus any passive or active comparison but the magnitude of depression reduction varied. Studies most often enrolled middle-aged adults; outcomes of depression severity in other age groups may differ. 

Findings related to implications for clinical decision-making

This growing body of evidence suggests that yoga may be an effective adjunctive intervention for adults struggling with depression. Clinicians and individuals would do well to be informed about the beneficial effects of yoga on depression severity. It is possible that a yoga-based intervention may be more readily available for some individuals experiencing depression and may find it more suitable to their needs and desires than some other treatment options. Some individuals may be more willing and able to implement this intervention independently which could be helpful to many individuals who are reluctant to consult a physician for this common, yet, often stigmatized disorder. 

.

 Research Gaps 

   Larger RCT studies which examine more severely-affected adults would better identify the magnitude of effect of yoga on depression severity than could be determined in this review. Most studies only tested a total of 58 or fewer individuals. Having larger groups may provide a tighter confidence intervals around estimates of effect. 

Three out of eight studies did not provide a p value to determine whether the observed changes within groups were statistically significant, as is common with pilot studies 9,11,15.

Five out of eight studies were over 70% female, so studies with a stronger male participation may be helpful in providing recommendations. 9-11,13,14

Various types and doses of yoga were used which could make it challenging to make a specific recommendation as to the ideal type and duration of practice. 

Larger studies with more severely-affected adults that focus on the type of yoga that produced the greatest effect would help determine whether yoga might be beneficial for those more severely affected by depression. Subgroups which would most likely benefit from therapies should also be determined. 

Trials were relatively long which may not be feasible for adults more severely affected by depression. Shorter trials of the type of yoga associated with the greatest improvements in depression would advance clinical applicability.

Finally, it would be helpful if future studies focused on finding which yoga and adjunctive or concomitant therapies provide the greatest improvements.

 Review Study Strengths

       Strengths of this review include a patient-reported outcome of primary importance to patients and families, and our focus on RCT evidence for an accessible non-drug intervention to improve clinical outcomes for this common mental health condition.

 Limitations

We acknowledge some review limitations. PubMed was used exclusively for the search; other databases were not included. The exclusion of systematic reviews may have eliminated some aggregated evidence. Treatment duration and intensity varied across studies which limited comparability. Nonetheless, this paper provides an overarching summary of recent research regarding the effect of yoga on depression which may be useful for informing intervention suggestions for adults dealing with depression.

Conclusions 

     Yoga results in small, short-term, beneficial effects on depression severity. Future studies with larger samples that focus on longer term effects and combined interventions could improve knowledge and applicability of results. 

For full paper with CHARTS, view this google doc: https://docs.google.com/document/d/16xgSnZ4KLzWoWygnLCMh7EjDaU_X5r7-MMVlkO0nLUk/edit?usp=sharing

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