Elsevier

Journal of Affective Disorders

Volume 202, 15 September 2016, Pages 67-86
Journal of Affective Disorders

Review article
Exercise as a treatment for depression: A meta-analysis

https://doi.org/10.1016/j.jad.2016.03.063Get rights and content

Highlights

  • Physical exercise is an effective treatment for unipolar depression.

  • Exercise compares favorably to no intervention and usual care for depression.

  • Exercise is comparable to psychotherapy and antidepressants for depression.

  • Exercise could be a viable adjunct and augmentation to antidepressants for depression.

  • Exercise may serve as an alternative to established treatments and waiting list.

Abstract

Background

This meta-analysis of randomized controlled trials (RCTs) examines the efficacy of physical exercise as treatment for unipolar depression, both as an independent intervention and as an adjunct intervention to antidepressant medication.

Methods

We searched PsycINFO, EMBASE, MEDLINE, CENTRAL, and Sports Discus for articles published until November 2014. Effect sizes were computed with random effects models. The main outcome was reduction in depressive symptoms or remission.

Results

A total of 23 RCTs and 977 participants were included. Physical exercise had a moderate to large significant effect on depression compared to control conditions (g=−0.68), but the effect was small and not significant at follow-up (g=−0.22). Exercise compared to no intervention yielded a large and significant effect size (g=−1.24), and exercise had a moderate and significant effect compared to usual care (g=−0.48). The effects of exercise when compared to psychological treatments or antidepressant medication were small and not significant (g=−0.22 and g=−0.08, respectively). Exercise as an adjunct to antidepressant medication yielded a moderate effect (g=−0.50) that trended toward significance.

Limitations

Use of the arms with the largest clinical effect instead of largest dose may have overestimated the effect of exercise.

Conclusions

Physical exercise is an effective intervention for depression. It also could be a viable adjunct treatment in combination with antidepressants.

Introduction

According to the World Health Organization (WHO), depression is a global disease, with over 350 million people affected (WHO, 2012). The WHO estimates that depression will be the second leading cause of global burden of disease worldwide by 2020 (WHO, 2001). Major depressive disorder (MDD) is the most prevalent mental disorder (Kessler et al., 2005, Wittchen and Jacobi, 2005), with a lifetime prevalence of 6–15% (Bromet et al., 2011). Depression is one of the most common diagnoses in primary health care (WHO, 2001). Depression reduces health more than somatic diseases such as arthritis, angina, and diabetes do (Moussavi et al., 2007), and depression was one of the leading causes of disability in 2012 (WHO, 2012). The mortality rate of depression is about 4%, which is equivalent to that of smoking (NICE, 2013). For patients suffering from somatic diseases such as cancer, cardiovascular diseases, and infections, the mortality risk increases even further with comorbid depression (Mykletun et al., 2009).

Guidelines from the National Institute for Health and Care Excellence (NICE) recommend the psychological treatments cognitive behavioral therapy (CBT) or interpersonal therapy (IPT) as treatment of choice for mild to moderate depression, followed by antidepressant medication (NICE, 2013). Many patients do not achieve sufficient symptom relief despite adequate treatment implementation (Bahr, 2009), and 50% experience at least one new depressive episode (Helsedirektoratet, 2009). Research points to the importance of maximizing the response to treatment as early as possible due to declining prognosis with depression duration and failed treatment responses (NICE, 2013; Trivedi et al., 2006). A subsequent treatment is often required to increase the effect (Major et al., 2011), either by changing treatment or by adding one (Wisniewski et al., 2007). Given the serious consequences of depression, cost-effective and robust interventions to establish recovery and prevent relapse are crucial.

Both the WHO (WHO, n.d.) and the NICE guidelines (NICE, 2013) recommend implementing physical exercise (henceforth referred to as exercise) in the standard treatment of depression. It is thus important to have updated knowledge on the effect of exercise on depression. Several reviews provide support for the antidepressant effect of exercise (Blake et al., 2009, Bridle et al., 2012, Cooney et al., 2013, Josefsson et al., 2014, Krogh et al., 2011, Mura et al., 2014, Rethorst et al., 2009, Robertson et al., 2012, Silveira et al., 2013). However, most of these previous reviews (Blake et al., 2009, Bridle et al., 2012, Cooney et al., 2013, Josefsson et al., 2014, Mura et al., 2014, Rethorst et al., 2009, Robertson et al., 2012) have not distinguished between depressive symptoms and depression as a diagnosis fulfilling certain diagnostic criteria according to the Diagnostic and Statistical Manual of Mental Disorders (DSM) or the International Classification of Diseases (ICD). In evaluation of the efficacy of exercise as a treatment in a clinical setting, Krogh et al. (2011) advocate that inclusion of studies should be limited to those including participants with a diagnosis of depression. To the best of our knowledge, the meta-analyses by Krogh et al., 2011, Silveira et al., 2013 are the only ones that have investigated the effect of exercise on depression exclusively in participants with a diagnosis of unipolar depression. However, Krogh et al. and Silveira et al. completed the search for articles in 2008 and 2011, respectively, and Silveira et al. included nonrandomized controlled trials. Hence, an update in this important domain is warranted, and we seek to fill this gap. In an attempt to increase the generalizability of the knowledge about treatment for the depressed population that most commonly needs health care, we include only studies on participants with a diagnosis of unipolar depression.

The majority of the previous meta-analyses compared exercise with different types of controls (waiting list, placebo, other treatment). This is common practice, but complicates the interpretation of results, as exercise compared to other treatments is likely to yield smaller effect sizes than exercise compared to no intervention. The terms “no intervention”, “waiting list”, and “usual care” have been used interchangeably in previous reviews and studies (for instance, in Rethorst et al., 2009, Sims et al., 2009). Furthermore, the term “usual care” can encompass a range of interventions of varying efficacy (Freedland et al., 2011). It is important to ascertain the relative effect of exercise on depression in this regard, as the probability of response to treatment and prognosis decreases with duration of depression (NICE, 2013), and because many patients with depression go untreated or undertreated (González et al., 2010; Health and Social Care Information Centre and Community and Mental Health statistics team, 2014; WHO, 2012). Rethorst et al. (2009) included only no-intervention or waiting list controls; however, they also included nonclinical participants. To investigate whether exercise could provide symptom relief while awaiting access to the treatments of choice for depression, we specifically compare exercise groups to no-treatment or waiting list controls. Since we believe that no intervention or waiting list is different from usual care, we include a separate analysis with usual care controls. To assess the effect of exercise compared to treatments recommended by the NICE (2013), we also compared exercise to psychological treatments and antidepressant medication. Rethorst et al., 2009, Cooney et al., 2013 have also compared exercise to these controls, but as previously described, they also included nonclinical participants in their analyses. Thus, the present study is, to the best of our knowledge, the first meta-analysis to compare the effects of exercise with these control conditions for patients with unipolar depression.

Due to declining prognosis with depression duration and failed treatment responses (NICE, 2013), the need for maximizing the effect of interventions for depression is paramount. The WHO recommends exercise in combination with antidepressants or psychotherapy (WHO, n.d.), and a recent review indicates that exercise in combination with antidepressants can be effective (Mura et al., 2014). To the best of our knowledge, no meta-analysis has previously investigated this in a population suffering from unipolar depression. We therefore assess the relative effect of the combined treatment of antidepressant medication and exercise for persons with unipolar depression.

The Cochrane Library has published several comprehensive and rigorous reviews regarding the effect of exercise on depression (Cooney et al., 2013, Mead et al., 2009, Rimer et al., 2012). We have extended and aimed to complete the thorough electronic searches executed in these Cochrane reviews to provide an exhaustive compilation of studies according to our current research aims. Unlike these previous Cochrane reviews, we will only include studies in which participants had a clinical diagnosis of unipolar depression.

Considering both the frequent occurrence and the severe impact of depression, updated knowledge on a readily available intervention, such as exercise, is highly warranted, and the objective of the present meta-analysis is to investigate the effect of exercise as a treatment for unipolar depression. We will examine the effect of exercise compared to active control conditions (psychological treatments and antidepressant medication), as well as to usual care and to no intervention. We will also assess the effect of exercise as an adjunct to treatment with antidepressant medication. These five comparisons have not previously been specifically investigated for patients suffering from the common and severe diagnosis of unipolar depression.

Section snippets

Eligibility criteria

We evaluated randomized controlled trials (RCTs) published in Norwegian, Danish, Swedish, English, and Spanish for inclusion. The allocation of participants to conditions had to be described as randomized, including terms such as “randomly”, “randomization”, and “random”, and the exercise group had to be compared to a control group.

Participants

The participants were adults 18 years or older, of both genders, in any setting, and with a diagnosis of unipolar depression according to DSM- or ICD criteria. Some

Results of the literature search

The electronic searches yielded 3346 records. After deletion of duplicates, we screened records to exclude obvious nontarget records manually, before reading abstracts and continuing to remove irrelevant records. Search in additional sources yielded one study written in Persian (Rashidi et al., 2013), which we unfortunately were not able to evaluate. Further, we did not manage to obtain the results from an unpublished manuscript (Reuter et al., 1984) included in some previous meta-analyses (

Discussion

The current meta-analysis is the first to determine the efficacy of exercise for patients suffering from unipolar depression compared to the most common and real alternatives for these patients: psychological treatment, antidepressant medication, usual care, and no intervention. This is important, as a large proportion of these patients do not seek or receive recommended treatment for their depression, or they prefer an alternative treatment to established treatments. It is also the first

Conclusions

Findings from the current meta-analysis indicate that exercise is an effective intervention for depression compared with various types of controls. The effect of exercise as an independent treatment is evident, and the effect is particularly high when compared to no intervention. Thus, exercise may serve as an alternative for patients who do not respond to the given treatment, patients who are awaiting treatment, or those who for different reasons do not receive or want traditional treatment.

Potential conflict of interest

All authors declare that they have no conflict of interest.

Acknowledgements

All authors declare that they have no conflict of interest. This meta-analysis was funded by a research grant from the District General Hospital of Førde. The funding source had no influence on the design, execution, or interpretation of the meta-analysis. We are grateful to the following authors for being so helpful and forthcoming to our enquires: James Blumenthal, Rebecca A. Gary, Jesper Krogh, Jorge Mota-Pereira, Felipe Schuch, Egil W. Martinsen. We thank librarian Kjersti Aksnes-Hopland at

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