Mead GE, Morley W, Greig CA, McMurdo M, Lawlor DA. Exercise for Depression. Cochrane Database Syst Rev. 2009 Oct 8;(4):CD004366.
This study was a meta-analysis reviewing the effect of exercise on depression. The authors looked only at prospective randomized controlled trials that investigated the effect of exercise on depressive symptoms. The authors separately analyzed exercise versus “no treatment” and exercise versus alternate treatments for depression. Alternate treatments included pharmacotherapy, psychotherapy, and “bright light” therapy. The meta-analysis of all included studies showed a large effect of exercise on depressive symptoms in those diagnosed with clinical depression when compared to no treatment. When only trials with blinded outcome assessments were included, the effect of exercise on depressive symptoms was moderate in magnitude. Similarly, when only trials with intention to treat analysis were looked at, the effect was moderate but still of statistical significance. Only three trials were deemed to have adequate randomization, blinded outcome assessment and intention to treat analysis; among these studies, exercise did have an effect on depressive symptoms but not to a statistically significant degree. In those trials that followed subjects for an extended period of time, the effect of exercise was found to decrease after participants stopped exercising, indicating that the benefits of exercise may be gradually lost.
The authors included studies looking at any type of exercise versus no treatment, as well as studies comparing any type of exercise plus an intervention (eg, cognitive behavior therapy), versus that intervention. Studies comparing two or more exercise types with no treatment were excluded. The authors also excluded studies with so-called “combination treatments” where exercise was combined with another treatment and compared to no treatment.
Depressive symptoms were defined by varying measures. Trials that measured depressive symptoms, on either a continuous or dichotomous scale, at baseline and at the outcome assessment, were included. When multiple measures of depressive symptoms were used in a single study, the primary outcome was used. The primary outcome was defined by a hierarchy of criterion: identified by the authors as the primary outcome, outcome reported in the abstract, or outcome first reported in the results section.
This meta-analysis examined the effect of exercise on depressive symptoms. Many trials excluded participants who did not suffer from clinical depression. The authors purposely focused on the effect of exercise on the poor end of the mood spectrum. Although exercise may also benefit those without depressive symptoms, this meta-analysis did not specifically address that subset of people.
The authors included randomized controlled trials that examined the following:
• exercise versus no exercise/waitlist/placebo
• exercise versus established treatment for depression (i.e., pharmacotherapy, psychotherapy, bright light therapy).
• exercise plus an intervention versus the same intervention.
The authors identified a total of 144 relevant papers and excluded 116 for not meeting criteria. The 116 excluded studies included 67 prospective trials. In order to minimize the risk of bias, the authors rated trials on whether 1) allocation was concealed 2) outcome assessors were blinded and 3) the intention to treat analysis was performed. Only three trials were found to meet all three criteria.
This comprehensive meta-analysis of prospective studies found that exercise has a moderate to large effect on depressive symptoms, but that this effect wears off after participants stopped exercising, indicating that the benefits of exercise may be lost unless exercise is continued long-term.
Atlantis E., Chow, C.M., Kirby A., Singh M.F. An effective exercise-based intervention for improving mental health and quality of life measures: a randomized controlled trial. Preventive Medicine 39 (2004) 424-434.
This study investigated the effect of a 24 week exercise-based intervention on self-reported measures of mental health and quality of life. The intervention involved a program of aerobic and weight-training exercise plus behavior modification. 73 subjects were recruited from a group of Australian casino employees. Psychological and quality of life data were collected using the DASS (Depression Anxiety and Stress Scale), and SF-36 Health Status Survey. The study concluded that multi-modal exercise (aerobic+weight training) improves self-reported measures of stress and quality of life. Moreover it was found that multi-modal exercise is as effective as single-modal exercise for depressive symptoms.
The primary outcome measures in this study were self-reported measures of mental health and quality of life. Mental health was measured using the DASS (Depression Anxiety and Stress Scale), while quality of life was measured using the SF-36 Health Status Survey. The “exercise-based intervention” involved a 24 week program of both aerobic exercise and weight-lifting regimen.
Participants of this study were Australian casino employees who had no previously diagnosed medical or psychiatric conditions. As a result, the results of this study cannot be generalized to individuals with previously diagnosed medical or psychiatric conditions. In addition, the fact that all the study subjects were recruited from a single workplace was less than ideal.
It cannot be ignored that this study looked at the impact of multi-modal exercise; subjects participated in aerobic training and weight-training, received motivational feedback from supervisors, and attended health education seminars. The results of this study, therefore, do not necessarily apply to those who engage in exercise who do not receive motivational feedback and encouragement. Some of the positive effects of the “exercise-based intervention” may have been due to this feedback and increase in social activity. The results of this study cannot be properly generalized to those who engage in an exercise program who do not receive motivational feedback.
Participants were told they were participating in a trial looking at the effect of exercise on “overall health.” There was no concealment in this particular study. Researchers were aware of which participants had been placed into which treatment group. Studies that investigate the effect of an intervention that requires active participation (such as exercise) cannot have a true “placebo” control, and the participants cannot be blinded. Due to the active nature of the intervention, participants were aware of whether they were part of the treatment or control group. The researchers therefore could not control for the “Hawthorne effect,” that is that subjects may change their behavior simply because they are being studied.
Participants were randomized into permuted blocks and were stratified for gender, abnormal scores on any one of three psychological constructs using the Depression, Anxiety and Stress Scales. All participants were recruited from a group of 3800 Star City casino employees (Australia) who were not currently participating in aerobic or weight-training exercise for 20-min duration more than 2 days/week, or in the 3 month-period preceding.
Dropout rate: 12 of 36 were lost to follow up in the treatment group, 13 of 37 were lost to follow up in the wait-list control group. Out of the 73 participants recruited, almost 40% dropped out of the study. The high drop-out rate of the study threatens the internal validity of the study. Those who had less depressive symptoms may have been more likely to continue in the program.
This study had significant limitations and the results cannot be generalized to those who exercise and do not receive positive reinforcement and health education. Nevertheless, the results of this study supported the hypothesis that a combination of aerobic exercise, weight training, positive motivational feedback, and health education may improve mental health and overall quality of life.
Stubbe J.H., de Moor D.I., de Geus E.J.C. The association between exercise participation and well-being: A co-twin study. Preventive Medicine 44 (2007) 148-152.
This study investigated the association and causality between leisure-time exercise participation and self-reported measures of well-being. The association of regular exercise and well-being was assessed in 8000 subjects from the Netherlands Twin Registry. Causality was tested in 162 monozygotic twin pairs, 174 dizygotic twin and sibling pairs, and 2842 unrelated subjects. The study concluded that those who engaged in regular exercise were more satisfied with their life and “happier” than non-exercisers. In addition, the results of the study indicated that this association is non-causal and may be mediated by genetic factors that influence both exercise behavior and well-being.
Study subjects were divided into “exercisers” and “non-exercisers” based on whether they participated in leisure time exercise at least once every month. Exercise was defined as any leisure time activity with a minimum intensity of four metabolic equivalents (METs), where one MET represents the rate of energy expenditure of an individual at rest. Physical activity in the workplace or related to household tasks did not classify as leisure time exercise.
Subjective well-being was divided into “life satisfaction” and “happiness.” “Life satisfaction” was measured with a Dutch adjusted version of the five-item Satisfaction With Life Scale, while “happiness” was measured with a Dutch adjusted version of the four-item Subjective Happiness Scale.
Satisfaction With Life Scale:
Participants respond on a scale from one (strongly disagree) to seven (strongly agree):
In most ways my life is close to my ideal.
The conditions of my life are excellent.
I am satisfied with my life.
So far I have gotten the important things I want in life.
If I could live my life over, I would change almost nothing.
Subjective Happiness Scale:
Participants respond on a scale from one (strongly disagree) to seven (strongly agree).
In general, I consider myself a happy person.
Compared to most of my peers, I consider myself less happy.
In general I am very happy.
I enjoy life regardless of what is going on, getting the most out of everything.
In general I am not very happy.
Although I am not depressed, I never seem as happy as I might be.
A potential limitation of the co-twin control method is that the results of the twin samples may not generalize to a non-twin population. The authors accounted for this by comparing twins and their singleton brothers and sisters; no specific “twin effects” were found.
Participants/Recruitment: All subjects were part of a longitudinal study on health and lifestyle in twin families registered with The Netherlands Twin Registry. Three specific groups of twin, twin-sibling, or sibling pairs were formed in which one member of the pair exercised regularly and the other did not.
The results of this study found that those who exercise in their leisure time at least once a month are, on average, more likely to identify themselves as being happy and satisfied with their lives. The results from the co-twin control analysis, however, argued against a causal effect of exercise participation. Identical twins who did not exercise reported being just as happy and satisfied with their lives as their genetic counterparts who did exercise. This pattern was less pronounced in fraternal twins. The results of this study therefore suggest that there may be underlying genetic factors that influence both exercise behavior and well-being.
Hassmen P., Koivula N., Uutela A. Physical Exercise and Psychological Well-Being: A Population Study in Finland. Preventive Medicine 30 (2000) 17-25.
This study was a cross-sectional investigation of the association between physical exercise frequency and psychological well-being. A total of 3403 participants answered questions regarding their exercise habits, perceived health and fitness, and mental well-being. The Beck Depression Inventory, State-Trait Anger Scale, Cynical Distrust Scale, and Sense of Coherence inventory were used to assess mental well-being. The results of the study found that those who exercise at least two to three times a week experienced significantly less depression, anger, cynical distrust, and stress than those exercising less frequently or not at all. Moreover, those who exercise regularly were also found to have a higher sense of coherence and stronger feeling of social integration.
Exercise frequency was determined by asking study participants “How often do you exercise physically in your spare time for at least 20-30 minutes to the extent that you at least slightly lose your breath and perspire?” Possible choices included “daily, two to three times per week, once a week, two to three times a month, a few times a year, and cannot perform exercise due to illness or handica p.”
Mental-well being was assessed using the Beck Depression Inventory, the State-Trait Anger Scale, the Cynical Distrust Scale, and the Sense of Coherence Inventory.The study population included participants aged 25-64, and thus the results cannot properly be generalized to individuals outside this age range. Participants included stratified random samples of 2000 individuals each, 25-64 years of age, and were drawn from the Finnish cardiovascular risk factor survey.
This was a cross-sectional study, and as such, the association rather than the cause-effect relationship between exercise and psychological well-being was studied. The survey did not account for physical activity that occurs in the workplace or as part of household activities. Exercise was defined as physical activity during one’s spare time. The study may thus have underestimated the overall prevalence of physical activity in the study population.
This study found a significant association between increasing frequency of exercise and improved measures of psychological well-being. As a cross-sectional study, this study did not attempt to establish whether a cause-effect relationship existed. Nevertheless, physically active participants were found to experience less depression, less suppressed anger, less cynical distrust, and stronger sense of coherence in comparison to those who exercised less frequently.
Blumenthal J.A., Babyak M.A., Moore K.A., Craighhead W.E., Herman S., Khatri P., Waugh R., Napolitano M.A., Forman L.M., Appelbaum M., Doraiswamy P.M., Krishnan K.R. Effects of Exercise Training on Older Patients With Major Depression. Arch Intern Med 159 (1999) 2349-2356.
This study looked at the extent to which exercise training may reduce depressive symptoms in older patients with major depressive disorder. 156 participants were assigned randomly to program of aerobic exercise, antidepressant medication (sertraline), or combined exercise and medication. These subjects underwent an evaluation of depressive symptoms, before and after treatment, using the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) criteria, Beck Depression Inventory, and Hamilton Rating Scale for Depression. This study found that after 16 weeks of treatment the groups did not differ significantly in their depressive symptoms.
This study looked at the effect of exercise on symptoms of major depressive disorder. Major depressive disorder was defined according to the DSM-IV criteria, which includes depressed mood or loss of interest/pleasure and at least 4 of the following symptoms: sleep disturbance, weight loss or change in appetite, psychomotor retardation or agitation, feelings of worthlessness or excessive guilt, impaired cognition or concentration, and recurrent thoughts of death.
The exercise intervention consisted of three supervised exercise sessions per week for a period of 16 weeks. Each session consisted of 45 minutes of aerobic activity.
The study investigated the effect of aerobic exercise on individuals with major depressive disorder. As such it cannot be generalized to the population at large. The authors of this study chose to focus on older individuals with significant psychopathology, and did not include those who fall within the normal range of psychological well-being. Moreover the authors of the study excluded participants with a psychiatric diagnosis other than major depressive disorder.
The exercise interventions occurred in a group setting with professional supervision. Some of the positive effects of the “exercise-based intervention” may have been due to an increase in social activity. The results of the study, therefore, cannot be properly generalized to those who exercise as individuals without social interaction.
This was a short-term study of 16 weeks. It remains unknown whether the improvement in depressive symptoms in all three treatment groups would have persisted over the long-term. The results are applicable only to the short-term treatment of major depressive disorder.
Group exercise was compared to medication (sertraline) alone vs. a combination of medication and exercise. There was no true no-treatment control group. Participants were randomized into stratified groups to ensure roughly proportionate numbers of mildly and moderately to severely depressed patients were assigned to each treatment group.
“Every effort was made” to blind clinical raters to the patients’ treatment group. As with other studies that investigate the effect of an intervention that requires active participation (such as exercise), participants were aware of which treatment group they had been assigned to. Participants in the exercise-only group were not given placebo medication.
156 patients aged 50-77 who met criterica for MDD were recruited through flyers, media advertisements, and letters sent to local physicians and mental health facilities. Dropout rate, including those lost to follow up: 32 patients (20.5%). There was no significant difference in dropout rates across treatment groups.
All three groups exhibited a significant decline in depressive symptoms after the 16 weeks of treatment. 60.4% of patients in the exercise group, 68.8% of patients in the medication only group, and 65.5% of patients in the combination group no longer met DSM-IV criteria for MDD at the conclusion of the study. The results of the study, therefore, supported the notion that a group program of aerobic exercise may be an effective treatment for depression in older adults. Of note, the presence of clinical depression did not preclude the vast majority of subjects from participating in an exercise program. Although there was no true no-treatment control group, previous studies have estimated that approximately 30% of patients with MDD respond to placebo. The patients in this study who participated in group exercise, therefore, showed an approximately two-fold greater response than those who received placebo.