Is yoga an evidence-based therapy for depression?
Jacinta Brinsley is completing her PhD in exercise physiology at the University of South Australia under primary supervision of Kade Davison and co-supervised by myself and Danielle Girard. This week I present the first study in her research program on yoga for depressive symptoms: a systematic review of the area to date.
The review included randomized controlled trials (RCTs) of yoga as an intervention for depressive symptoms in adults that could have been part of any mental disorder, including problems like alcohol use disorders or psychotic disorders. Much like “cognitive behaviour therapy”, a wide variety of practises have been subsumed under the label “yoga” and a key theme of Jacinta’s work has been to call for more transparency and consistency in describing the intervention actually delivered in a study. In this systematic review, Jacinta defined yoga as “a structured, formal and premeditated form of physical activity involving the integration of specific body movements (asana) with breathing (pranayama) and/or mindfulness (including meditation), where the movement component made up more than 50% of the total physical intervention” (p.2). In addition to the effects on self-reported depressive symptoms, Jacinta was also interested in the effects on physiological parameters and acceptability.
There were 19 RCTs but 6 did not report depression scores so could not be included in the meta-analysis. The 19 RCTs encompassed n=1080 participants, 69% women, with the most common diagnostic groups represented being antenatal depressive disorder and schizophrenia (present in 5 studies each). The yoga interventions employed were typically hatha or unspecified, with an average duration of 2.4 months, 1.6 sessions x 60 minutes per week, and supervised by yoga practitioners in 17 of the studies.
The meta-analysis found a moderate effect of yoga on depressive symptoms compared to all control groups combined. The standardized mean difference of -0.41 [-0.65, -0.17] equates to an average difference between those receiving yoga and those receiving the control condition of about 3 points on common self-report measures (e.g., Beck Depression Inventory, K10, PHQ-9). However, analysing studies by type of control group revealed that yoga only showed a significantly greater effect when compared to wait-list control groups. Yoga was no more effective in reducing depressive symptoms than treatment as usual or attention controls such as health education, yoga education, bibliotherapy or social support. By contrast, authoritative meta-analyses find that cognitive behaviour therapy has larger effects on depressive symptoms than time on a wait list (g = 0.98 [0.80 , 1.17] – comparable to a 7-point difference on most depression self-report measures) and although the advantage over treatment as usual is smaller, it remains moderate and statistically significant (g = 0.60 [0.45, 0.75] – approximately 4 points on common self-report measures) (Cuijpers, Cristea, Karyotaki, Reijnders, & Huibers, 2016). Yoga appeared to have its largest effect sizes for schizophrenia but this is most likely because both these studies compared yoga to wait list control. The moderate effect for depressive disorders appears more promising because it was based on 8 studies, only one of which employed wait list as the control. Few studies found significant advantages for yoga on physical measures and there were too few studies to calculate pooled effect sizes. Of 7 studies that took physical measurements, one found yoga improved physical strength more than treatment as usual and one study found more improvement on a questionnaire about health functioning than wait list control.
So, is yoga an evidence-based therapy for depressive symptoms? I hate that question. How strong is the empirical support that yoga is helpful for depressive symptoms? At the moment, not very strong. Jacinta rated 53% studies as high quality, however the scale used was very basic and psychotherapy studies are usually critiqued to a higher standard. For example, the quality scale does not consider whether attention control conditions actually match the active condition (yoga) for time, there were no such luxuries as whether diagnosis was confirmed by separate assessors with inter-rater reliability checks, and the scale makes no reference to whether yoga was delivered competently or not. Only 36% studies reported intent-to-treat analyses, a red flag that reported results are likely not going to be representative of results clinicians in routine practice can expect to obtain. Crucially though, the lack of comparison against ‘bona fide’ interventions and the uncertainty as to what actually occurs in the yoga conditions mark the state of the literature as relatively immature. In the face of these quality deficits, the meagre effect sizes are even less impressive.
Take home: Clinical Implications
Yoga may have a moderate effect on reducing depressive symptoms in people with depressive disorders compared to very basic interventions like psychoeducation. There were no adverse effects of yoga and drop-out rates were no worse than typical in psychotherapy. There is no harm in referring clients to yoga as an adjunct to a psychological or physical intervention with strong empirical support.
It is not safe to assume that all interventions are equally effective. Yoga does not have the same level of support as CBT and other psychotherapies. Yoga should not be offered instead of CBT or other empirically supported interventions.
Clinicians should not consider a suggestion that clients take up yoga at discharge from a treatment service when they still have clinically significant depressive symptoms to be sufficient treatment. Psychiatric review, a second course of psychotherapy which has shown to be effective for clients who have failed to respond to a first course, aerobic physical exercise programs, treatment of comorbid sleep disorders or medication trials would all be more appropriate courses of action.
Absence of evidence is not the same as evidence of absence. Yoga may be an awesome treatment for depressive symptoms. It’s just that the studies conducted to date do not demonstrate this conclusively yet. If you’re passionate about yoga, join Jacinta’s efforts to build its evidence base.
Go to https://bjsm.bmj.com/content/early/2020/04/05/bjsports-2019-101242 for the original article
References
Brinsley, J., Schuch, F., Lederman, O., Girard, D., Smout, M., Immink, M.A., Stubbs, B., Firth, J., Davison, K., & Rosenbaum, S. (2020). Effects of yoga on depressive symptoms in people with mental disorders: a systematic review and meta-analysis.British Journal of Sports Medicine, 0, 1-10. doi:10.1136/bjsports-2019-101242.
Cuijpers, P., Cristea, I. A., Karyotaki, E., Reijnders, M., & Huibers, M. J. H. (2016). How effective are cognitive behavior therapies for major depression and anxiety disorders? A meta-analytic update of the evidence. World Psychiatry, 15(3), 245-258. doi:10.1002/wps.20346