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Review: exercise may moderately improve depressive symptoms

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QUESTION

Question:

How effective is exercise as a treatment for depression?

Outcomes:

Symptoms of depression (continuous or dichotomous outcomes).

METHODS

Design:

Systematic review with meta-analysis.

Data sources:

MEDLINE, EMBASE, PsycINFO, Sports Discus, Cochrane Controlled Trials Register, Cochrane Database of Systematic Reviews, hand search of BMJ, JAMA, Arch Intern Med, N Engl J Med, J R Soc Med, Compr Psychiatry, Br J Psychiatry, Acta Psychiatr Scand, Br J Sports Med and of bibliographies of all retrieved articles; search to March 2007.

Study selection and analysis:

Two reviewers independently selected and appraised randomised controlled trials of any type of exercise as a treatment for depression. Inclusion criteria: adults aged 18 years and over with depression (any method of diagnosis and any severity), studies comparing exercise with no treatment (wait-list or placebo, such as social activity) or with any other intervention (including medication, psychotherapy or complementary therapies), or where exercise was an adjunct treatment compared against the treatment without exercise (see online notes for exclusion criteria). Two independent reviewers extracted data and assessed study quality. Missing details were sought through author contact. Standardised mean differences of post treatment symptom scores and scores at follow-up were used as a measure of effect size. Heterogeneity was assessed using the χ2 test and I2 statistic, and a random effects model (DerSimonian and Laird’s method) was used to calculate pooled effect size. Subgroup analyses were performed for different types of exercise (aerobic, resistance or mixed).

MAIN RESULTS

Twenty-eight studies were eligible for inclusion, 19 of which were fully published. Six were doctoral dissertations and three were published in abstract form only. Twenty-five studies were included in meta-analyses. Many of the trials had multiple treatment arms and the majority recruited participants from non-clinical populations (eg, recruitment through the media). Clinical interview (nine studies) or depression scale cut-off point (12 studies) was used to diagnose depression in most of these studies. Most studies were evaluating aerobic exercise (including running, walking, aerobic training with instructor, aerobic dance, cycling). Interventions ranged from 10 days to 16 weeks in duration. Compared with no treatment (wait-list or placebo), exercise significantly reduced depressive symptoms post-treatment and at follow-up although this became non-significant when only blinded trials using allocation concealment and intention to treat analyses were included (see online table). Pooled analysis of six trials found no difference between exercise therapy and cognitive therapy while one found that exercise was superior to bright light therapy. Two trials found no significant difference between exercise therapy and antidepressants.

Table 1 Reduction in symptom severity at post-treatment and follow-up for exercise therapy compared with various interventions

CONCLUSIONS

Exercise may improve depressive symptoms in people with a diagnosis of depression but this effect is not significant when only methodologically robust studies are analysed.

ABSTRACTED FROM

Mead GE, Morley W, Campbell P, et al. Exercise for depression. Cochrane Database Syst Rev 2008;4:CD004366.

Additional notes and a table are published online only at http://ebmh.bmj.com/content/vol12/issue3

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Footnotes

  • Source of funding: NHS Lothian, University of Edinburgh, UK

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