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Running Away from Depression:

Can Exercise Really Treat the Disease?

Stephanie Coe

October 24, 2008

The Basics of Depression

            Depression is a mental disorder in which a person experiences a persistent low mood and a loss of interest in normally enjoyable activities.   The disease can have serious impacts on a person’s life, often affecting work, relationships, sleep, appetite, and health in general. As the lifetime prevalence of depression is seventeen percent in the U.S., considerable efforts have been made in the search for cures or treatments (http://en.wikipedia.org/wiki/Clinical_depression).

            Doctors or mental health professionals can diagnose a patient with depression.  After medical conditions are ruled out as the cause of symptoms, psychological evaluations are performed.  If a patient is diagnosed with depression, medication and psychotherapy are the most common treatments.  Unfortunately, depression is not fully understood, and diagnosis and treatment of depression are far from perfect (http://www.nimh.nih.gov/health/publications/depression/complete-publication.shtml#pub10).

Exercise and Depression

            Exercise is also commonly described as a treatment for depression.  Research on the effects of exercise on depression date back nearly 200 years, and 90% of studies show depression relief effects after exercise (http://www.overcoming-depression.com/depression-and-exercise.html).  Research shows that walking is actually one of the best exercises to treat depression.  Other aerobic activities such as swimming, softball, and biking have also been found helpful, as well as even weight-lifting, yoga, and taekwondo (http://www.depression-help-for-you.com/depression-and-exercise.html).  Thirty minutes of exercise three to five days a week is a common belief of the amount of exercise needed for long term improvements (http://www.cnn.com/HEALTH/library/MH/00043.html).  However, even a single thirty minutes workout can lead to feelings of well-being (http://www.ahealthyme.com/topic/exdepression).

Rationale

            There are many rationales as to why exercise can work to treat depression.  It is believed to increase a person’s sense of mastery, which helps people who do not feel in control of their lives and moods.   Self-esteem, which is often low in those suffering from depression, is also improved.  Exercise provides a distraction from worries, improves health and body, and thus the mood, helps get rid of built-up stress, and help a person sleep better, which is significant because difficulty sleeping is a symptom of depression (http://exercise.about.com/cs/exercisehealth/a/depression.htm).  Also, because experiences and their connected emotions are stored in parts of the body, muscle activity can release old, negative feelings.  Endorphins, which are pain-killers of the body, are released during exercise; they can help to alleviate some of the pains that come with depression (http://www.overcoming-depression.com/depression-and-exercise.html). Further, exercise can elevate the body temperature, which can be soothing, and affect levels of mood-enhancing neurotransmitters in the brain (http://www.cnn.com/HEALTH/library/MH/00043.html). 

Claims on Effectiveness

            It has been claimed that exercise can be just as effective in alleviating depression as antidepressants, individual psychotherapy, cognitive psychotherapy, and group psychotherapy.  Also, exercise is supposed to have a quick effect on decreasing the symptoms of depression, with one study even showing improvements in mood after ten minutes.  Another study showed a decrease in depression symptoms in a shorter amount of time than the effects of antidepressants begin to take place.  Follow-up studies have even shown that the effects last months after the quitting of exercise.  Benefits of exercise on depression found in studies include increased positive mood, less anxiety, less fatigue, improved motivation, increased feelings of social integration, and many more positive effects. (http://www.depression-help-for-you.com/exercise-and-depression.html).

            These claims are not made by exercise companies, but instead by websites devoted to helping those suffering from depression.  Information appears to be presented to help people with depression help themselves and to help people with depressed loved ones provide support. 

Research

            When keywords exercise and depression are searched in online databases, numerous studies, of various methods and outcomes, can be found.  Paluska and Schwenk (2000) performed a Medline search to find articles on exercise and depression in writing a review paper on the subject.  They analyzed meta analyses and review studies in addition to experimental and descriptive studies in search for conclusive evidence on whether or not exercise can reduce symptoms of depression.  A few of their conclusions were that regular physical activity can alleviate symptoms of depression, that strength and flexibility training are as effective as aerobic in treating depression, and that for the treatment of mild to moderate symptoms of depression, exercise is as effective as psychotherapy.  They believe physical activity deserves consideration as part of a treatment regimen for depressed patients.

            One study Paluska and Schwenk reviewed analyzed effects of aerobic training on depression in a group of forty three hospitalized, depressed patients.  Significant decreases in Beck Depression Inventory (BDI) scores were found after nine weeks of vigorous activity.  A second study reviewed followed fifteen depressed patients whose BDI and Profile of Moods States scores had not improved during a pre-exercise control phase.  After a ten week vigorous exercise program, the patients’ scores significantly decreased, again showing evidence of exercise’s ability in treating depression.  Meta analyses of clinically depressed subjects showed decreases in depressive symptoms after both short and long amounts of exercise.  Another study compared effects of running versus various psychotherapies and found running to be just as effective.  Conflicting studies, however, were analyzed.  Some found no additional benefits to combining exercise and therapy while others found additional benefit to using multiple treatments.

            Numerous studies on psychological mechanisms as explanations for the impact of exercise on depression were reviewed.  In many studies, the distraction hypothesis was believed to explain the connection, suggesting diversion from unpleasantness and painful complaints improves the mood after exercise.  The distraction from negatives of daily life created by exercise could be what leads to its positive effects.  Other studies showed that adopting the task of exercise improved self-efficacy and thus gave subjects improved moods and self confidence.  The mastery hypothesis indicates that a sense of independence and success are gained by the subject’s successfully following an exercise regimen.  Further studies found social support gained from fellow exercisers could also play a part in exercise alleviating symptoms of depression.

            Physiological mechanisms were also analyzed as potential causes of exercise’s effect on depression.  The monoamine hypothesis sees exercise as enhancing brain aminergic synaptic transmission, which is the effect many antidepressants are believed to have.  The endorphin hypothesis is also supported in many studies reviewed, claiming endorphins are released throughout the body and reduce pain while generating a euphoric state.

            Although they find exercise to be an effective treatment for depression, Paluska and Schwenk also warn about overtraining.  They describe studies showing how patients with anorexia nervosa can take exercise too far in effort to lose weight, how over exercising can decrease libido, and how it can lead to psychomotor retardation, which mimics depression.

            Though Paluska and Schwenk analyze many papers in studies in their review paper, a flaw affecting readers is that they do not give detailed descriptions of how they determine whether a study includes sufficient planning and control to yield accurate and precise results.

            In a twenty week, randomized controlled trial, Singh, Clements, and Singh studied 32 elderly subjects to test the effectiveness of unsupervised exercise as a long-term treatment for clinical depression.  During the first ten weeks, subjects were treated with supervised weight-lifting exercises three days a week, while during the second ten weeks, they were instructed to engage in exercise on their own.  If during the second ten weeks patients did not average exercising two times per week, they were not included in the study.  The control group watched health education videos during the first ten weeks and was given no instructions for the second.  Participants were assessed with the BDI at the end of the twenty weeks and again at a 26 month follow-up.  Compared to controls, the BDI of treated participants fell significantly at both twenty weeks and 26 months.  The researchers concluded that not only does exercise reduce symptoms of depression, but that unsupervised weight lifting maintains antidepressant effectiveness at twenty weeks and that progressive resistance training is a safe treatment.  Of course, this study used elderly patients and so cannot definitively claim exercise is an effective treatment for depression for all ages, but it is certainly a piece of evidence pointing in the right direction.  Another study, however, was mentioned in which the same mode of exercise was shown to be effective in younger patients.

            Tsang, Chan, and Cheung (2008) were not as confident in finding exercise to reduce depression.  They developed a review paper, analyzing randomized controlled trials that tested the effects of exercise on depression.  After searching five electronic databases, fifty-two studies were screened to be eligible for inclusion.  Only twelve, however, were kept due to weaknesses of the other studies such as being non-systematic reviews, non-randomized studies, and studies without a comparison group.  Based on the twelve randomized controlled trials found eligible for review, they found that exercise reduced depression levels or depression symptoms in the short-run.  Only one of the twelve studies did not find positive results on depression.  They also found, however, that the studies used too small of sample sizes and did not report maintenance effects.  They concluded that more well-controlled studies are needed to come up with conclusions of the long-term effects of exercise on depression.

            In another study, a prospective, randomized controlled trial with allocation concealment and blinded outcome assessment was performed with 202 adults diagnosed with depression (Blumenthal et al. 2007).  Inclusion factors included that participants were diagnosed with depression before the beginning of the study and that they did not regularly exercise.  The Hamilton Depression Rating Scale was given to subjects at baseline and again after four months of treatment.  Participants were randomly assigned to one of four treatments, including supervised exercise in a group setting, exercise at home, antidepressant medicine, or a placebo pill, for four months.  Out of patients treated with medication, 47% no longer met criteria for depression at the end of the study, while 45% of patients treated with supervised exercise and 40% treated with at home exercise no longer met criteria.  Only 31%, however, of placebo-treated patients went into remission.  Though these results appear to show effectiveness of exercise in treating depression at a rate close to that of medication, with a p value of .23, the placebo group did not yield significantly different results from the other three.  The researchers concluded that exercise led to a similar reduction in depression as medication, but that patient expectations plays a large role in the depression reductions found from all treatments.  A flaw of this experiment was the use of placebo controls instead of wait-list controls.  If reduction in depression with exercise as a treatment had been compared to reduction in depression of subjects on a wait list, significant results could possibly have been found.

            While many studies show decreases in symptoms of depression with exercise, not all support the belief that exercise causes reduced depressive symptoms.  In a population-based longitudinal study in a sample of families with twins, De Moor, Boomsma, Stubbe, Willemsen, and de Geus (2008) tested the causal effects of exercise on depressive symptoms.  Causal effects were tested with 5952 twins and 1206 other family members by longitudinal modeling of changes in exercise behavior and symptoms of depression, genetic modeling of the association between exercise and symptoms of depression, and analyzing intrapair differences between identical twins.  Through mailed questionnaires sent every two to three years, they found that the twin who exercised more did not show fewer depressive symptoms, and that increases in exercise participation did not predict fewer symptoms of depression.  Their study, however, was not without flaw.  They did not instruct subjects to exercise, but instead monitored their exercise and depression levels.  It is possible that if instead in their study they had instructed a control group not to exercise and the other group to exercise, different results would have been found.  There could be reasons related to depression that could explain why people do or do not exercise.  Also, because it was an observational study, there could have been variables confounded with exercise that could have caused there not to be a significant difference in depression between people who exercised and those who didn’t.

Summary

            While claims that exercise reduces depressive symptoms are upheld in many studies, others find no causal relationship; more studies need to be done before a conclusive answer can be given.  However, enough studies have been found supporting the belief that exercise can treat depression that it should be included in a treatment regimen for depressed patients, not necessarily replacing more tradition methods such as antidepressants and psychotherapy, but added as an additional step patients can take to feelings better.

            The various claims made about the mechanism by which exercise treats depression are supported in some studies while not in others.  It appears that exercise could treat depression in a variety of ways, possibly having positive effects through both psychological and physiological mechanisms.  More research should be done to give an exact answer to why exercise can possibly alleviate depressive symptoms, but why it may work is less important than that it may work, so exercise should still be used as a treatment. 

            Exercise is already proven to have many beneficial outcomes related to health, so even though the evidence of whether exercise truly causes depression relief and how it works is far from complete, it would still be a beneficial treatment for depressed patients.  Basic exercise safety, however, should be practiced.  Overtraining, while not appearing to be a major issue in the studies reviewed, is possible and can lead to negative health outcomes in patients.  Also, as with often recommended before a person beginning to exercise, it is important to first talk to a doctor about one’s individual risks.

References

http://en.wikipedia.org/wiki/Clinical_depression

http://www.nimh.nih.gov/health/publications/depression/complete-publication.shtml#pub10

http://www.overcoming-depression.com/depression-and-exercise.html

http://www.depression-help-for-you.com/depression-and-exercise.html

http://www.cnn.com/HEALTH/library/MH/00043.html

http://www.ahealthyme.com/topic/exdepression

http://exercise.about.com/cs/exercisehealth/a/depression.htm

http://www.depression-help-for-you.com/exercise-and-depression.html

Blumenthal, JA, MA Babyak, M Doraiswamy, L Watkins, BM Hoffman, KA Barbour, S Herman, WE Craighead, AL Brosse, R Waugh, A Hinderliter, A Sherwood, 2007.  Exercise and Pharmacotherapy in the Treatment of Major Depressive Disorder.  Psychosomatic Medicine 69: 587-596.

De Moor, MHM, DI Boomsma, JH Stubbe, G Willemsen, EJC de Geus, 2008.  Testing Causality in the Association Between Regular Exercise and Symptoms of Anxiety and Depression.  Archives of General Psychiatry 65: 897-905.

Paluska, SA, TL Schwenk, 2000.  Physical Activity and Mental Health: Current Concepts.  Sports Medicine 29: 167-180.

Singh, NA, KM Clements, MAF Singh, 2001.  The Efficacy of Exercise as a Long-term Antidepressant in Elderly Subjects: A Randomized, Controlled Trial.  Journal of Gerontology 56A: M497-M504.

Tsang, HWH, EP Chan, WM Cheung, 2008.  Effects of Mindful and Nonmindful Exercises on People with Depression: A Systematic Review.  British Journal of Clinical Psychology 47: 303-322.

 

 

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