A collection of postings on a range of issues is available on our website (www.mjacksongroup.ca).  This month’s post is again from Ken Pope’s listserv, where he kindly provides daily summaries of current articles in the field.

The British Medical Journal includes a study: “Effect of exercise for depression: systematic review and network meta-analysis of randomised controlled trials” byMichael Noetel, et al.

Here’s how it opens:

“Major depressive disorder is a leading cause of disability worldwide 1 and has been found to lower life satisfaction more than debt, divorce, and diabetes2 and to exacerbate comorbidities, including heart disease, 3 anxiety,4 and cancer.5 Although people with major depressive disorder often respond well to drug treatments and psychotherapy,67 many are resistant to treatment.8 In addition, access to treatment for many people with depression is limited, with only 51% treatment coverage for high income countries and 20% for low and lower-middle income countries. More evidence based treatments aretherefore needed.”

Here’s how the Discussion opens:

In this systematic review and meta-analysis of randomised controlled trials, exercise showed moderate effects on depression compared with active controls, either alone or in combination with other established treatments such as cognitivebehaviour therapy.

In isolation, the most effective exercise modalities were walking or jogging, yoga, strength training, and dancing. Although walking or jogging were effective for both men and women, strength training was more effective for women, and yoga or qigong was more effective for men. Yoga was somewhat more effective among older adults, and strength training was more effective among younger people.
The benefits from exercise tended to be proportional to the intensity prescribed, with vigorous activity being better. Benefits were equally effective for different weekly doses, for people with different comorbidities, or for different baseline levels of depression. Although confidence in many of the results was low, treatment guidelines may be overly conservative by conditionally recommending exercise as complementary or alternative treatment for patients in whom psychotherapy or pharmacotherapy is either ineffective or unacceptable. Instead, guidelines for depression ought to include prescriptions for exercise and consider adapting the modality to participants’ characteristics and recommending more vigorous intensity exercises. 

Our review did not uncover clear causal mechanisms, but the trends in the data are useful for generating hypotheses. It is unlikely that any single causal mechanism explains all the findings in the review. Instead, we hypothesisethat a combination of social interaction,61 mindfulness or experiential acceptance, 62 increased self-efficacy,33 immersion in green spaces, 63 neurobiological mechanisms,64 and acute positive affect65 combine to generate outcomes. Meta-analyses have found each of these factors to be associated with decreases in depressive symptoms, but no single treatment covers all mechanisms. Some may more directly promote mindfulness (eg, yoga), be more social (eg, group exercise), be conducted in green spaces (eg, walking), provide a more positive affect (eg, “runner’s high'”), or be more conducive to acute adaptations that may increase self-efficacy (eg, strength).66 Exercise modalities such as running may satisfy many of the mechanisms, but they are unlikely to directly promote the mindful self-awareness provided by yoga and qigong. Both these forms of exercise are often practised in groups with explicit mindfulness but seldom have fast and objective feedback loops that improve self-efficacy. Adequately powered studies testing multiple mediators may help to focus more on understanding why exercise helps depression and less on whether exercise helps.We argue that understanding these mechanisms of action is important forpersonalising prescriptions and better understanding effective treatments.
Here are the “Clinical and Policy Implications”:

Our findings support the inclusion of exercise as part of clinical practice guidelines for depression, particularly vigorous intensity exercise. Doing so may help bridge the gap in treatment coverage by increasing the range of first line options for patients and health systems.9 Globally there has been an attempt to reduce stigma associated with seeking treatment for depression.74 Exercise may support this effort by providing patients with treatment options that carry less stigma.

In low resource or funding constrained settings, group exercise interventions may provide relatively low cost alternatives for patients with depression and for health systems. When possible, ideal treatment may involve individualised care with a multidisciplinary team, where exercise professionals could take responsibility forensuring the prescription is safe, personalised, challenging, and supported.

In addition, those delivering psychotherapy may want to direct some time towards tackling cognitive and behavioural barriers to exercise. Exercise professionals might need to be trained in the management of depression (eg, managing risk) and to be mindful of the scope of their practice while providing support to deal withthis major cause of disability.

Ken Pope