Research articles
Exercise treatment for depression: Efficacy and dose response

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Background

This study, conducted between 1998 and 2001 and analyzed in 2002 and 2003, was designed to test (1) whether exercise is an efficacious treatment for mild to moderate major depressive disorder (MDD), and (2) the dose-response relation of exercise and reduction in depressive symptoms.

Design

The study was a randomized 2×2 factorial design, plus placebo control.

Setting/Participants

All exercise was performed in a supervised laboratory setting with adults (n =80) aged 20 to 45 years diagnosed with mild to moderate MDD.

Intervention

Participants were randomized to one of four aerobic exercise treatment groups that varied total energy expenditure (7.0 kcal/kg/week or 17.5 kcal/kg/week) and frequency (3 days/week or 5 days/week) or to exercise placebo control (3 days/week flexibility exercise). The 17.5-kcal/kg/week dose is consistent with public health recommendations for physical activity and was termed “public health dose” (PHD). The 7.0-kcal/kg/week dose was termed “low dose” (LD).

Main outcome measures

The primary outcome was the score on the 17-item Hamilton Rating Scale for Depression (HRSD17).

Results

The main effect of energy expenditure in reducing HRSD17 scores at 12 weeks was significant. Adjusted mean HRSD17 scores at 12 weeks were reduced 47% from baseline for PHD, compared with 30% for LD and 29% for control. There was no main effect of exercise frequency at 12 weeks.

Conclusions

Aerobic exercise at a dose consistent with public health recommendations is an effective treatment for MDD of mild to moderate severity. A lower dose is comparable to placebo effect.

Introduction

The Global Burden of Disease study1 found that mild to moderate major depressive disorder (MDD) ranks second behind ischemic heart disease for years of life lost due to premature death or disability. Although effective pharmacologic and psychotherapeutic treatments for MDD are available, many people do not seek treatment or do not receive adequate treatment.2 National estimates indicate that only 23% of people with this disease seek treatment,2 and only 10% receive adequate treatment, in part because of the social stigma associated with treatment.3

Exercise may be a viable treatment because it can be recommended for most individuals, and does not carry a negative social stigma. However, exercise has not yet met established efficacy standards,4, 5 although some studies have demonstrated reductions in depressive symptoms with exercise.6, 7, 8, 9, 10 A recent randomized controlled trial (RCT)11 compared exercise, antidepressant medication, and combined medication and exercise in older adults with MDD and found that all treatments were effective. This study adequately diagnosed depression and treatment outcomes, but because exercise was done in a group setting, a question remains of whether social support influenced treatment response. Isolating the effects of exercise from social support, examining effects in different age groups, and quantifying the amount of exercise needed to reduce symptoms of MDD is important for establishing the efficacy of exercise as a monotherapy.

Using scores from the 17-item Hamilton Rating Scale for Depression (HRSD17)12, 13 as the primary outcome measure, our purpose was to test: (1) whether the mean change in HRSD17 score from baseline was greater after 12 weeks for active exercise conditions compared with an exercise placebo; and (2) whether there was a dose-response relation between the exercise doses and reduction in HRSD17 score. Secondary aims were to examine rates of treatment response (50% reduction in HRSD17 score) and rates of remission (HRSD17≤7).5, 14

Section snippets

Methods

The rationales for the study design and detailed methods have been published elsewhere15; the methods and design are briefly outlined here.

Results

Approximately 5% of the 1664 prescreened participants were ultimately randomized to treatment. Figure 1 shows the reasons for exclusion. A total of 80 participants were randomized to the four conditions—LD/3, LD/5, PHD/3, or PHD/5—or the exercise placebo control. For the two independent variables of energy expenditure and exercise frequency, this included 34 participants in the two LD conditions and 33 in the two PHD conditions, and 33 participants in the two 3-day/week conditions and 34

Discussion

The major finding was that the public health dose (PHD) of exercise is an effective monotherapy for mild to moderate MDD. In the efficacy analysis, mean HRSD17 scores at 12 weeks were reduced 47% from baseline for the PHD condition, significantly better than the LD and control conditions. Forty-six percent of participants in the PHD group had a therapeutic response to treatment, defined as a 50% reduction in baseline HRSD17 score, and 42% of the PHD group had remission of symptoms, defined as

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