Exercise Against Depression
Michal Artal, MD, with Carl Sherman
Series Editor: Nicholas A. DiNubile, MD
THE PHYSICIAN AND SPORTSMEDICINE - VOL 26 - NO. 10 - OCTOBER 2021
In Brief: Physical activity is a useful tool for preventing and easing depression symptoms. When prescribing exercise as an adjunct to medication and psychotherapy, the complexity and the individual circumstances of each patient must be considered. Hopelessness and fatigue can make physical exertion difficult, and some patients are vulnerable to guilt and self-blame if they fail to carry out a regimen. A feasible, flexible, and pleasurable program has the best chance for success. Walking—alone or in a group—is often a good option.
Primary care physicians frequently see depressed patients, varying from those who have transient symptoms that may be a normal reaction to the setbacks of everyday life to those who are clinically depressed and experience functional impairments that affect relationships, quality of life, ability to work, and physical health.
Fortunately, depression is one of the most treatable mental disorders. Used judiciously, psychotherapy and antidepressant medication alleviate symptoms, effect remissions, and may prevent relapse in most patients. Exercise also has a significant role to play: It can complement traditional treatments in those who are clinically depressed and help prevent depression in those who do not have the illness (see "Exercise as a Depression-Prevention Tactic," below).
A Vital Primary Care Role
Depression is the most common mental disorder (1) and is further classified as major depressive disorder, bipolar disorder, dysthymic disorder, or depressive disorder not otherwise specified (2). Major depression is twice as common in women as in men (3,4).
The somatic symptoms of depression (eg, fatigue, sleeplessness, decreased appetite, decreased sexual interest, weight change, and constipation) bring many people to their primary care physicians. Depressed individuals are more likely than others to develop cardiovascular disease and to die of all causes (5). An estimated 15% of those with severe depression will commit suicide.
Research has consistently shown that 6% to 8% of all outpatients in primary care settings suffer from major depression (6). According to the National Ambulatory Medical Care Survey (7), more than 7 million primary care visits were made annually in the early 1990s for the treatment of depression, double the number 10 years earlier. Half are treated by primary care physicians and half by psychiatrists (1).
Despite the large numbers of patients diagnosed as having depression, the disease remains underdiagnosed (8), and, according to one study (1), only one third of those having the diagnosis were receiving treatment.
The Exercise-Depression Link
Research on physical activity and depression goes back to the 19th century. In recent decades, many studies have documented the benefits of exercise on mood in healthy and clinically depressed individuals.
Methodologic problems in many of the studies make interpretation and application of the findings difficult (1,9,10). Some studies used heterogeneous patient populations, mixed samples of healthy and clinically depressed subjects, or used different clinical instruments to measure depression and its alleviation. Many studies refer to depression as a homogeneous entity rather than a spectrum of disorders that vary in severity, etiology, and biologic and psychosociologic complexity.
Several studies did not differentiate the types of therapeutic interventions with which exercise was compared, while asserting that exercise was equal to or more beneficial than other treatments (11-13). In particular, these studies did not differentiate between the different types of psychotherapy (ie, individual, group, hospital-based milieu, brief, or long-term).
Despite methodologic problems, most studies have found exercise to have psychological and physiologic benefits for participants, with 90% of studies reporting antidepressant and anxiolytic effects (9). Taken as a whole, the research strongly suggests that benefits are greatest in individuals who have greater psychological impairment and in those who are clinically depressed (10), but both clinical and nonclinical populations benefit.
Clinical populations. Studies in clinically depressed populations have included both hospitalized and ambulatory patients. One study (14) of hospitalized depressed patients found significant reductions in depression among patients who were prescribed an aerobic exercise program, but not in a control group who participated in occupational therapy. Another study (15) randomly assigned patients to 8 weeks of walking and jogging, recreational therapy, or a waiting list. Depression scores decreased only in the walking and jogging group.
There is no evidence that any one kind of exercise has a greater impact on depression than others, though many studies have used running or other aerobic activities. In one trial (16), 40 depressed women were randomly assigned to 8 weeks of running, a weight-lifting program, or a waiting list. Members of both exercise groups were less depressed than the control group at the end of the trial and at later follow-ups; results between the exercise groups were similar. The authors concluded that a positive outcome did not depend on achieving physical fitness. Other studies reached the same conclusion. In a study (11) of hospitalized depressed patients, mood and fitness improved after a walking or jogging program, but there was no correlation between changes in the two parameters.
Nonclinical populations. Exercise benefits have also been seen in people who are not clinically depressed but are at high risk for depression or have some depressive symptoms (17-20).
One study (21) examined 55 college students who had had a high number of stressful life events in the previous year. The students were assigned to aerobic exercise training, relaxation training, or no treatment; after the 11-week program, the exercisers scored lower on a standard depression inventory than the other two groups. Another trial (22) involved 43 college women who manifested substantial mood symptoms that fell short of actual depression. They were randomized to participate in 10 weeks of regular aerobic exercise (1 hour, twice a week), relaxation training, or no exercise. Reductions in depression scores were significantly and consistently greater in the aerobics group.
In nonclinical populations, as in clinically depressed patients, most studies found that aerobic and nonaerobic exercise were equally beneficial (23).
Why Does Exercise Help?
How exercise alleviates depression remains unclear. Psychological and physiologic effects have been suggested.
Psychologically, exercise may enhance one's sense of mastery, which is important for both healthy and depressed individuals who feel a loss of control over their lives. A meta-analysis of 51 studies (24) linked exercise to a small but significant increase in self-esteem. Exercise may provide a therapeutic distraction that diverts a patient's attention from areas of worry, concern, and guilt (25).
In addition, improving one's health, physique, flexibility, and weight may all enhance mood. Many exercisers report that their ability to eat more freely without worries about gaining weight also increases pleasure, satisfaction, and a sense of self-control.
Another benefit is that large-muscle activity may help discharge feelings of pent-up frustration, anger, and hostility.
Researchers continue to study the effects of exercise on the neurochemistry of mood regulation. They are focusing on metabolism and turnover of monoamines and other central neurotransmitters at presynaptic and postsynaptic sites and their role in the mediation of depression. Antidepressant medications, including the selective serotonin reuptake inhibitors (SSRIs), are believed to exert an antidepressant effect by increasing the availability of neurotransmitters at receptor sites. Exercise may exert its beneficial effect on mood by influencing the metabolism and availability of central neurotransmitters (26-28). A recent study (29) reports that acute exercise increases brain serotonin.
The role of beta-endorphins in mood regulation has received considerable attention. These endogenous chemicals, which reduce pain and can induce euphoria, have been linked to the "runner's high" experienced by intensive exercisers. The ability of exercise to produce enough beta-endorphins to affect depression remains questionable (30). Several authors (31,32) report elevated levels of beta-endorphins after acute exercise; however, the elevations in fit individuals are lower than in those who are not fit.
One study (33) compared 11 elite runners with a matched group of meditators. After each group engaged in running or meditation, researchers compared them by mood and circulating levels of beta-endorphin and corticotropin-releasing hormone (CRH). Mood and CRH were elevated after both activities, but beta-endorphin was elevated only in the runners, which suggests that an increase in beta-endorphins is not necessary for mood elevation.
Because disturbed sleep is both a symptom of depression and an aggravating factor, the beneficial effects of exercise on sleep may be very important. A recent controlled clinical trial (34) involving 32 older adults (ages 60 to 84) who had major depression or dysthymia demonstrated that a 10-week program of weight training exercise (three times per week) significantly improved all subjective sleep quality and depression measures. Another controlled study (35) of 43 men and women (ages 50 to 76) reported improvement in sleep disturbances after 16 weeks of moderate-intensity exercise. Investigators, however, noted the potential confounding effects of uncontrolled variables such as outdoor light, time of day, and their effects on circadian rhythms; environmental heat; and fitness of the subjects (36).
The Exercise Prescription
When designing an exercise prescription for patients who have depression, several caveats apply.
Anticipate barriers. Common symptoms of depression—fatigue, lack of energy, and psychomotor retardation—may pose formidable barriers to physical activity. Feelings of hopelessness and worthlessness may also interfere with motivation to exercise.
Keep expectations realistic. Exercise recommendations should be made cautiously. Many depressed patients have a tendency toward self-blame and may see exercise as another occasion for failure. Suggest that physical activity may be quite useful, but do not raise false expectations that can arouse anxiety and guilt. Explain that exercise may be an adjunct to, not a substitute for, primary treatment. A patient eager to escape the stigma and shame surrounding emotional illness (feelings that tend to increase during depression) may want to minimize the condition by viewing exercise as a way to avoid antidepressants and psychotherapy.
Introduce a feasible plan. An exercise prescription should be realistic and practical, not an additional burden that may compound the patient's sense of futility. (See the Patient Adviser, "Mobilize Against Depression.") Consider the individual's background and history. For patients who are severely depressed, exercise may need to be postponed until medication and psychotherapy begin to alleviate symptoms. Patients who have been sedentary should start with a light exercise schedule: for example, just a few minutes of walking each day.
When patients find it difficult to start exercising, one might communicate that time is on their side. With treatment, symptoms will yield, and what seems impossible today may become easier 2 or 3 weeks later.
Accentuate pleasurable aspects. The specific choice of exercise should be guided by the patient's preferences and circumstances. The activity must be pleasurable and easily added to the patient's schedule. Exercise enjoyment has been shown to facilitate adherence (33).
When appropriate, group activities (eg, exercise classes, walking groups) should be encouraged. Depressed patients who are isolated and withdrawn are likely to benefit from increased social involvement. The stimulation of being outdoors and in a pleasant setting may enhance mood, and exposure to light has been shown to be therapeutic in seasonal depression.
State specifics. Walking is almost universally acceptable, carries minimal risk of injury, and has been shown to be beneficial for mood enhancement. In keeping with recent American College of Sports Medicine (ACSM) recommendations for healthy adults (37), a goal of 20 to 60 minutes of walking or other aerobic exercise, three to five times a week, is reasonable. The ACSM also recommends resistance training 2 to 3 days per week and flexibility training 2 to 3 days per week. (See "ACSM Makes Exercise Advice More Flexible: Fitness Recommendations Updated," August, page 16.)
Encourage compliance. More—more intense, more frequent—is not necessarily better. Improved fitness may be a valuable consequence of exercise but is not necessary for an antidepressant effect; however, greater antidepressant effects are seen when training continues beyond 16 weeks (13). Compliance is likely to be better when the exercise prescribed is less demanding, and one study (38) has linked more intensive programs with increased tension and anxiety. In fact, the "staleness" that some athletes experience with overtraining resembles depression (39).
Integrating Exercise With Other Treatments
The primary treatments for depression should not present exercise obstacles. Antidepressant medication is frequently prescribed when depression impairs a patient's ability to function. Older tricyclic antidepressants, such as imipramine hydrochloride and amitriptyline hydrochloride, often cause orthostatic hypotension and sedation, which can impair aerobic activity. Tricyclics may cause dangerous arrhythmias in athletes (39).
The newer antidepressants (eg, fluoxetine hydrochloride, sertraline hydrochloride, paroxetine hydrochloride, nefazodone hydrochloride, and venlafaxine hydrochloride) have better side-effect and safety profiles. Frequently, they are first-choice agents and appear to be compatible with exercise.
The spectrum of brief and long-term psychotherapies is widely used for depression, either alone or with antidepressant medication. An exercise prescription makes a useful contribution to psychotherapy when the goal is to increase patients' overall activity level and add pleasurable, satisfying experiences. The patient's difficulties with exercise, such as motivational problems, fear of interpersonal situations, and/or a tendency to transform exercise into a burdensome chore, may shed light on dysfunctional attitudes that can be explored in psychotherapy.
Though exercise has few if any adverse effects, some patients may misuse exercise. Those who have anorexia nervosa may undertake extreme physical activity, driven by a disturbed body image. Individuals who are compulsive in other areas of their lives may become compulsive about exercise at the expense of personal relationships and increased injury risk.
These dangers may be obviated somewhat by stressing that exercise, like a prescribed drug, should be "taken as directed" and that more is not necessarily better. If dysfunctional attitudes are significant, they can be addressed in psychotherapy.
Exercise as a Depression-Prevention Tactic
When talking to patients about exercise, physicians can share information about its probable role in maintaining mental health. Physical activity may play an important role in preventing depression, according to the surgeon general's report on physical activity and health (1).
Cross-sectional epidemiologic studies (2,3) suggest a positive association between exercise and mental health but do not prove a cause-and-effect relationship. According to the surgeon general's report, people who have no mental health problems may be more likely to exercise.
Cohort studies shed light on whether physical activity prevents mental health problems. In one study (4) of 10,201 male Harvard alumni, low levels of activity reported during initial interviews (in 1962 or 1966) were inversely related to self-reported physician-diagnosed depression in 120218. The relative risk of depression was 27% lower for men who reported playing 3 or more hours of sports each week than for those who reported playing no sports. The Harvard alumni study, along with another cohort study (5), presents limited evidence for a dose-response association between levels of physical activity and depressive symptoms.
The surgeon general's report concludes that some evidence supports a protective role of exercise against depression, but more research is needed to confirm the protective effect and to determine the frequency, duration, and intensity needed to improve mental health.
Dr Artal is an assistant professor of psychiatry at Saint Louis University in Missouri. Mr Sherman is a freelance writer in New York City. Dr DiNubile is an orthopedic surgeon in private practice in Havertown, Pennsylvania, specializing in sports medicine and arthroscopy. He is the director of Sports Medicine and Wellness at the Crozer-Keystone Healthplex in Springfield, Pennsylvania; a clinical assistant professor in the department of orthopedic surgery at the University of Pennsylvania in Philadelphia; the orthopedic consultant to the Philadelphia 76ers basketball team and the Pennsylvania Ballet; and a member of the editorial board of The Physician and Sportsmedicine. Address correspondence to Michal Artal, MD, Saint Louis University Health Sciences Center, 1221 S Grand Blvd, St Louis, MO, 63104; e-mail to [email protected].
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