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The effectiveness of exercise as an intervention in the management of depression: systematic review and meta-regression analysis of randomised controlled trials |
Lawlor D A, Hopker S W |
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Authors' objectives To determine the effectiveness of exercise as an intervention in the management of depression.
Searching The following databases were searched: MEDLINE from 1966 to 1999; EMBASE from 1980 to 1999; SPORTDiscus from 1975 to 1999; PsycLIT from 1981 to 1999; the Cochrane Controlled Trials Register; and the Cochrane Database of Systematic Reviews. The search terms used were 'exercise', 'physical activity', 'physical fitness', 'walking', 'jogging', 'running', 'cycling', 'swimming', 'depression', 'depressive disorder' and 'dysthymia'. In addition, the authors examined bibliographies, contacted experts, and handsearched copies of the following journals published in the 12 months to December 1999: BMJ, JAMA, Archives of Internal Medicine, New England Journal of Medicine, Journal of the Royal Society of Medicine, Comprehensive Psychiatry, British Journal of Psychiatry, Acta Psychiatrica Scandanavica, and British Journal of Sports Medicine.
Study selection Study designs of evaluations included in the reviewOnly randomised controlled trials were eligible for inclusion.
Specific interventions included in the reviewStudies which compared exercise with other established treatments for depression were eligible for inclusion. Studies that compared different types of exercise were excluded.
Participants included in the reviewDepression. Studies that included participants aged 18 years or over with depression, diagnosed by any method and of any severity, were eligible for inclusion. Studies that included participants with anxiety or other neurotic disorders were excluded.
Outcomes assessed in the reviewStudies that included depression as an outcome measure were eligible for inclusion. Studies that measured the outcomes immediately before and after a single exercise session were excluded.
How were decisions on the relevance of primary studies made?Three reviewers independently reviewed the titles and abstracts to retrieve potentially relevant studies.
Assessment of study quality The quality of the studies was assessed by noting whether allocation was concealed, whether an intention to treat analysis was undertaken, and whether there was blinding (see Other Publications of Related Interest nos.1-2). The assessment was described in full in the paper. Two reviewers independently assessed the quality of the included studies.
Data extraction Two reviewers independently extracted the following data: participant details, intervention details, outcome measures, baseline and post-intervention results, and main conclusions. The data were extracted onto a structured form, and any discrepancies were resolved by referring to the original papers and through discussion.
The authors calculated effect sizes for each trial, using Cohen's method (see Other Publications of Related Interest no.3) and a standardised mean difference for the overall effect.
Methods of synthesis How were the studies combined?First, a narrative synthesis of the data from all of the studies was undertaken. Meta-analysis and meta-regression analysis of those studies with appropriate data were also conducted. The data were presented as the standardised mean difference (SMD) with 95% confidence intervals (CIs).
How were differences between studies investigated?The effect of exercise compared with 'no treatment' was considered separately from the effect of exercise compared with an established treatment for depression.
Where heterogeneity was identified, the studies were combined using a random-effects model (see Other Publications of Related Interest no.4).
Results of the review Fourteen studies were eligible for inclusion: 8 studies compared an exercise group with a no treatment group, while 6 studies compared exercise directly with an established form of therapy (3 studies also included a no treatment group).
The majority of studies were judged to be of poor quality.
Exercise compared with placebo intervention or as an adjunct to standard treatment: of the 11 studies, 10 had data available for analysis. The pooled SMD, calculated using the random-effects model, was -1.1 (95% CI: -1.5, -0.6). The significant heterogeneity between the studies (Q=35.0, p<0.001) was associated with the type of publication and length of follow-up. The reported effect of treatment was significantly higher in [A:conference abstracts than in] peer-reviewed journals or doctoral dissertations. The length of follow-up was significantly, negatively associated with the size of the effect. Pooling 9 studies that used the Beck depression inventory as a measure of depression gave a weighted mean difference of -7.3 (95% CI: -10.0, -4.6). The significant heterogeneity found was associated with the type of publication and length of follow-up.
Exercise compared with standard treatments for depression: 4 out of 6 studies compared exercise with cognitive therapy. The SMD was -0.3 (95% CI: -0.7, 0.1). These studies were homogeneous. One study comparing exercise and standard antidepressant treatment found no significant difference on the Hamilton rating scale between participants receiving the exercise intervention and/or medication. The sixth study compared exercise with 'time limited' and 'time unlimited' psychotherapy, and found no significant difference between the three groups.
Authors' conclusions The effectiveness of exercise in reducing symptoms of depression cannot be determined because of a lack of good-quality research on clinical populations with adequate follow-up.
CRD commentary The methodology of this review was good. The authors set out a clear review question and reported detailed inclusion and exclusion criteria. The search was comprehensive and it was unlikely that any studies were missed, although the authors could have carried out an assessment of publication bias. The process of, and the number of reviewers who carried out the study selection and data extraction were reported. Study validity was adequately assessed and details of the studies were well presented in tables. The method of pooling was appropriate although the authors could have reported their methods more clearly. Heterogeneity was suitably assessed using a meta-regression model. The authors' conclusions follow from the data presented.
Implications of the review for practice and research Practice: The authors state that doctors could recommend more physical activity to their motivated patients, but that this should not replace standard treatment, particularly for those with severe disease.
Research: The authors state that there is a need for well-designed, randomised controlled trials on a clinical population. These trials should measure both continuous and dichotomous outcomes, and follow up participants for at least 12 months.
Bibliographic details Lawlor D A, Hopker S W. The effectiveness of exercise as an intervention in the management of depression: systematic review and meta-regression analysis of randomised controlled trials. BMJ 2001; 322: 763-767 Other publications of related interest 1. Moher D, Cook DJ, Eastwood S, Olkin I, Rennie D, Stroup DF, for the QUOROM Group. Improving the quality of reports of meta-analyses of randomised controlled trials: the QUOROM statement. Lancet 1999; 354:1896-1900. 2. Schulz KF, Chalmers I, Hayes RJ, Altman DG. Empirical evidence of bias. Dimensions of methodological quality associated with estimates of treatment effects in controlled trials. JAMA 1995;273:408-12. 3. Rosenthal R. Parametric measures of effect size. In: Cooper H, Hedges LV, editors. The handbook of research synthesis. New York: Russell Sage Foundation; 1994. 4. DerSimonian R, Laird N. Meta-analysis in clinical trials. Control Clin Trials 1986;7:177-88.
This additional published commentary may also be of interest. Stevinson C. Lack of quality research on exercise and depression. FACT 2001;6:209.
Indexing Status Subject indexing assigned by NLM MeSH Data Collection /standards; Depressive Disorder /rehabilitation; Exercise Therapy /methods; Humans; Randomized Controlled Trials as Topic /standards; Treatment Outcome AccessionNumber 12001001020 Date bibliographic record published 31/10/2002 Date abstract record published 31/10/2002 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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