Feeling down or sad occasionally is a typical response to situations in life; in contrast, in depression, such feelings become persistent and affect routine activities. Depression is a common chronic health condition that negatively affects physical, emotional, and social health and significantly interferes with daily functioning. In addition, the potential economic consequences and public health burden of depression are substantial. As with many other health conditions described in this book, research supports a beneficial role of physical activity in the prevention and treatment of depressive disorders.
Depression is more common than one might expect. Major depressive disorder, also referred to as unipolar depression or clinical depression, is the most common psychiatric disorder. Worldwide, 350 million people suffer from depression (36). Estimates suggest that approximately 7 percent of adults report a major depressive episode in the past year, and one in five U.S. adults has a mood disorder over the course of life, with major depression the most common (29, 30). According to the World Health Organization, depression is the leading cause of disability and global disease burden in industrialized nations (36). In addition to the tremendous impact of depression on individuals and families, the financial drain is immense. The economic costs of depression include medical costs such as increased frequency of medical visits, longer hospital stays, greater risk and severity of chronic health conditions, and premature death due to both suicide and poor medical outcomes (8), as well as workplace costs including absenteeism and reduced productivity while one is at work (also referred to as presenteeism) (53).
What Is Depression?
While everyone feels sad or down on occasion, someone with clinical depression has persistent symptoms that interfere with daily functioning. Symptoms of depression include these:
· Depressed mood or feelings of sadness
· Loss of interest or pleasure in previously enjoyed activities
· Changes in appetite (increase or decrease) or body weight (loss or gain)
· Changes in sleeping habits (sleeping too much or problems falling or staying asleep)
· Fatigue or loss of energy
· Feelings of hopelessness, worthlessness, or guilt
· Difficulty thinking or concentrating or not being able to make decisions
· Agitation, restlessness, or slowed movements
· Thoughts of suicide or death
To receive a diagnosis of depression, an individual must experience either low mood or loss of interest (first two items in the preceding list) and four or more of the remaining symptoms. In addition, these symptoms must be severe enough to affect daily activities, must persist for a period of two weeks or more, and must not be due to a physical illness or a substance (either drug of abuse or medication) (2).
Other mood disorders include persistent depressive disorder (dysthymia), bipolar disorder, and premenstrual dysphoric disorder (see table 20.1 for more information on each of these types) (2). Additionally, the childbearing period is a high-risk time for depression in women, so it is important to watch for signs of peripartum depression (occurring during pregnancy or within four weeks of delivery) and postpartum depression. Depression also frequently co-occurs with many chronic medical illnesses. Because depression may last for a long period of time and symptoms may be mistakenly attributed to stress or illness, it is important to talk to your doctor if you think you could be experiencing symptoms of depression.
While anyone can be affected by depression at any time, certain factors are associated with increased risk of developing depression:
· Being female
· Having a family history of depression
· Having experienced a previous bout of depression
· Having low social support or social isolation
· Having a chronic health condition
· Experiencing stressful life events
· Low levels of physical activity
Women are about twice as likely to suffer depression as men. People who have a family history of depression are more likely to suffer depression themselves. In addition, someone who has had a prior episode of depression is significantly more likely than others to experience a subsequent episode. Other risk factors include stressful life events, social isolation, and having a chronic health condition (40). Finally, being physically inactive has been shown to increase risk for depression, providing further support for the important role of physical activity in promoting mental as well as physical health (19). Having these risk factors does not mean that you will become depressed; however, if you are aware of the risk factors, you can be more alert to the signs and symptoms for yourself or loved ones.
Depression and Health
As previously mentioned, chronic health conditions have been associated with a higher likelihood of developing depression. People with chronic medical conditions, such as cardiovascular disease, stroke, diabetes, cancer, and pulmonary disease, commonly experience elevated symptoms of depression (26); and depression is also associated with increased risk for many chronic illnesses (28). Depression can interfere with glycemic control (i.e., maintaining normal glucose levels in the body), reduce immunity, and negatively affect the cardiovascular system (27). Because the symptoms of several chronic diseases may overlap with symptoms of depression, diagnosis can be problematic. However, depression that is not treated can lead to worse medical outcomes due to both psychological and physiological factors. Taking medication properly, seeking medical care, quitting smoking, eating a healthy diet, and getting adequate sleep are all more difficult if you are experiencing symptoms of depression (26). Individuals with a medical illness who may have symptoms of depression should speak with a doctor or a mental health professional to better understand the symptoms and how they might affect illness and treatment.
Treatment for Depression
There are a variety of treatments for depression, including antidepressant medications and psychotherapy. Antidepressants are not habit-forming drugs but work by correcting chemical imbalances in the brain. However, the exact mechanism of antidepressant medications is not fully known. Common antidepressant medications work to influence the brain in various ways. Some affect chemicals in the brain, including norepinephrine, serotonin, and dopamine. These medications include the older and now less commonly used monoamine oxidase inhibitors and tricyclic antidepressants, as well as the newer, safer selective serotonin reuptake inhibitors (SSRIs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) (49). Newer medications that have unique mechanisms of action (atypical antidepressants) or that combine different mechanisms of action (multimodal antidepressants) are commonly used. More recently, the use of antidepressant medications that target other brain chemicals, such as glutamate, or that target brain communication pathways related to depression has increased, with the hope of improving treatment outcomes (49).
Clinical and research experience has revealed that not every medication is effective for every person. Unfortunately, medication selection is often a “trial and error” approach, with challenges in matching individuals with the antidepressant medication that is most likely to benefit them. If you take an antidepressant medication, you may feel some improvement in the first couple of weeks, but the full benefits are not generally seen for a couple of months. It may take several attempts or even a combination of medications to find a prescription that fully relieves depression, so it is important to talk with your doctor about your medication and symptoms. Even after you get better, your doctor will want you to continue medication for a period of time to maintain improvement and protect against relapse (8).
Exercise can improve both physiological and psychological functioning.
In addition to potential difficulties of identifying the appropriate medication and dosage to relieve symptoms, side effects can be a frequent problem of medications, and they are often noticed before people feel relief of depression symptoms. Commonly reported side effects of antidepressant medications include changes in weight or appetite, headache, dizziness, nausea, sexual dysfunction, and sleep disturbances, although the type and severity of these symptoms vary depending upon the type of medication (4). Thus, if you are using a medication, it is important to have ongoing monitoring of the medication, side effects, and symptoms to ensure that successful remission is achieved and maintained (54). Routine and consistent monitoring of symptoms is recognized as very important in the management of other chronic diseases, and depression should be no exception. In what is referred to as “measurement-based care” (38), standardized scales are used to quantify the frequency and severity of symptoms, side effects, and adherence in order to aid in treatment.
Psychotherapy, including cognitive behavioral therapy and interpersonal therapy, can also effectively treat depression. Cognitive behavioral therapy focuses on developing problem-solving skills and changing negative or unhelpful thinking, and has been shown to be particularly effective as a psychological treatment for depression. Interpersonal therapy assists individuals through life transitions, grief, and other difficulties. As with medication, it may take some time to see significant improvement, and ongoing maintenance sessions may be necessary. There are different options for counseling formats, and family or group counseling may be helpful in addition to individual sessions. Finding a well-trained, experienced therapist or counselor is an important factor in the effectiveness of psychotherapy (32).
For more severe depression or when other treatments have not been adequate, electroconvulsive therapy may be indicated. This medical treatment involves stimulating the brain under anesthesia over a series of sessions and can be effective when other treatments have not been successful. Additional medical treatments involving specific stimulation of certain brain areas include vagus nerve stimulation, transcranial magnetic stimulation, and deep brain stimulation (8, 40). It is important for individuals to partner with their mental health professional to select a treatment that is appropriate for them and their individual situation.
Although more attention has been given to depression in recent years, adequate treatment remains problematic (36). Barriers include difficulty in finding an effective treatment and full relief of symptoms (8), as well as the cost of health care visits, medication, or psychotherapy. Thus, many avoid seeking treatment or discontinue treatment before full remission. Despite a greater understanding of depression, social stigma and accessibility to treatment are other commonly reported barriers to seeking treatment (8). Even among those who seek and receive treatment, many do not achieve full relief of symptoms. Without full relief of symptoms (remission), the risk of future episodes is increased (22). Therefore, the role of exercise in the prevention and treatment of depression is an important health issue.
Mental Health Resources
Help is available from many community resources, including these:
· Mental health professionals: psychiatrists (MD, DO), psychologists (PhD, PsyD), social workers (LSW, LCSW), and mental health counselors (LPC, MFT, LMHC)
· Physicians including family medicine, internal medicine, and obstetrics and gynecology
· Community mental health centers and clinics
· Social service agencies
· Religious organizations and clergy
Healthy Approaches to Managing Depression
Lifestyle factors can have a potential role in the prevention and treatment of depression. The value of a healthy diet and regular physical activity are discussed in the upcoming sections.
Focusing on Nutrition
Balanced nutrition is an important consideration in the treatment and prevention of depression. However, because changes in appetite and weight are a symptom of depression, nutrition can be particularly problematic. In addition, people with depression often have low motivation and difficulty planning and problem solving, which makes maintaining a healthy diet even more difficult. People who are feeling down, anxious, or stressed may make poor food choices for comfort, while other people may skip meals altogether. Some antidepressant medications are associated with weight gain, which is another reason physical activity is important.
For purposes of mental health, people should generally follow the recommended guidelines for nutrition according to their age and calorie needs (56) (see chapter 3 for dietary guidance). In addition, some evidence indicates that people with depression may have lower levels of omega-3 fatty acids, B vitamins (B12, folate), and other minerals and amino acids that affect brain function (48). A health professional or dietitian may recommend a vitamin supplement if your diet is not providing adequate nutrients.
Focusing on Physical Activity
Exercise is valuable for the prevention and treatment of a variety of medical conditions. Exercise can improve both physiological and psychological functioning. Exercise has also been shown to improve depressive symptoms in individuals with other chronic diseases including cancer (11), neurologic diseases such as Alzheimer’s disease and multiple sclerosis (1), and heart disease (42).
Several benefits of physical activity play a role in the interrelationship between mental and physical health. For example, feeling troubled or distressed is related to increased risk for mental illness as well as physical illnesses such as heart disease, and such feelings have a negative impact on one's quality of life. Physical activity and exercise training are generally associated with less distress and enhanced feelings of well-being (43). The benefits include these:
· Reduced depressive symptoms
· Reduced likelihood of future episodes of depression
· Improved sleep quality and reduced fatigue
· Improved cognitive function
· Decreased pain and somatic complaints
· Improved self-esteem and self-efficacy
· Improved quality of life and daily functioning
Exercise as a Treatment for Depression
Although the role of exercise in alleviating symptoms of depression has been proposed for centuries, researchers have accumulated evidence within the past several decades supporting the health benefits of exercise. Even for individuals who do not have clinical levels of depressive symptoms, consistent evidence shows a positive effect on mood with both acute bouts of exercise and longer-term exercise training. Exercisers often report feeling more energy, greater self-esteem, and less stress (43). However, people with depression tend to be less active and to have high amounts of sedentary time, and few achieve adequate levels of physical activity (23).
Physical activity such as walking has been found to be associated with a lower risk of developing depression (35). People who are more active report fewer depressive symptoms and reduced incidence of physician-diagnosed depression (15, 19). However, this type of research examines relationships, showing that higher levels of activity are associated with lower risk of depression. The direction of the relationship—does physical activity reduce depression or does depression result in less activity?—cannot be determined by associations alone. To answer this question, clinical research studies in which exercise is prescribed and risk of depression is then determined provide better insights on how physical activity can be used as an antidepressant therapy.
Overall, clinical research studies that use exercise as a treatment for depression show a clinically meaningful positive effect of exercise as an antidepressant therapy (31, 33, 37). Most of the research has used aerobic-type activities such as walking, jogging, or cycling, but there is evidence that resistance training and even yoga might be helpful. Several studies have reported that exercise alone can reduce depression symptoms comparably to traditional pharmacotherapy or psychotherapy in individuals with mild to moderate major depressive disorder (6, 18, 44, 51). However, only a few studies have examined the appropriate "dose" of exercise to achieve a reduction in symptoms. Available evidence suggests that the dose of exercise recommended for general health benefits, as described throughout this book, may also be effective to reduce depression symptoms (18, 43).
Achieving full relief of symptoms can be a challenge in the treatment of depression, and adding exercise to other treatments may be effective (55). Given the difficulty in obtaining full remission of depressive symptoms and the likelihood of future episodes, the use of exercise in combination with traditional therapies is promising but requires further study.
Supporting the inclusion of exercise, evidence suggests that exercise may directly improve particular symptoms of depression, specifically sleep, fatigue, and cognitive function. Sleep disturbances are a key feature of depression and can negatively affect health and daily functioning. Some evidence indicates that exercise may increase sleep time and sleep quality (41), and single bouts of exercise have been shown to enhance feelings of energy and reduce fatigue (16). Exercise training may be helpful in reducing symptoms of fatigue for both healthy adults and those with health conditions (45). Recent evidence also suggests that, when added to an antidepressant, various levels of exercise improve sleep quality and reduce awakening in the middle of the night and early morning (46). These benefits are in addition to the effects of exercise on the overall symptoms of depression. The following are other benefits:
· Low cost
· Convenience
· Accessibility
· Fitness and health benefits
· Few negative side effects
· Alterability of the routine to meet needs and goals
· Greater individual control
Cognitive function, such as learning, remembering, and using information, is frequently disrupted in depression and can create significant and persistent difficulties in daily functioning. Similar to the observations of exercise effects on sleep, various levels of exercise have been shown to directly improve cognitive functions, independent of changes in overall depressive symptoms. Higher levels of exercise have been associated with additional benefits, particularly with respect to spatial working memory, or tasks that measure how one works with visual and spatial information (21). However, there are few studies in this area, so more research is needed.
How Exercise May Affect Mental Health
The exact mechanisms by which physical activity improves mental health are largely unknown. But this is also the case for psychotherapy and medications. It is likely that antidepressant therapies work due to a combination of effects, including changes in thoughts, feelings, and brain pathways. There may also be a type of placebo or expectancy effect, with treatments working, in part, because patients believe that they will help. For example, if you are confident that exercise will lower depression, you may be more likely to see that outcome when engaging in exercise. Physical activity may also provide a distraction from worries or symptoms and reduce stress by offering a "time-out" from daily concerns, which can be very important in the management of depression and anxiety. Individuals who are successful in becoming more physically active commonly report improved self-confidence and enhanced self-esteem, and this can also enhance feelings of control. In a study of older adults, increases in self-esteem predicted decreases in depression symptoms after treatment with physical activity (39). Exercise may also provide additional opportunities for social support and interaction, which can be helpful for those suffering from depression (7).
In addition, biological adaptations in brain systems may contribute to the antidepressant effect of physical activity. Exercise appears to enhance the way the brain functions. Positive effects on mood and depression may be due to the impact of exercise on the brain chemicals norepinephrine and serotonin (10, 13, 14, 17, 20). Other studies have focused on proteins in the brain, called nerve growth factors, which promote growth and connectivity of nerve cells in the brain. Whether with reference to a single exercise session or to an established exercise routine, benefits have been identified related to various proteins in the brain that enhance mental health and function (e.g., brain-derived neurotrophic factor [BDNF] and VGF nerve growth factor) (24, 47). In addition, researchers continue to examine other substances (e.g., brain opioids) that may play a role in regulating mood and affecting mental disorders (7).
Physical Activity Recommendations
Although more research is needed to help guide exercise recommendations specific to the management of depression, there is good evidence that physical activity of different types and doses can be beneficial for mental health. Aerobic exercise, resistance training, and yoga have all been shown to help manage depressive symptoms.
Aerobic Exercise
The current evidence suggests that an exercise program that meets the recommendations in chapter 5 is also beneficial for mental health (5, 18, 43). Most research regarding exercise and depression has focused on aerobic modes of exercise, including walking, jogging, and stationary cycling. A good initial target for aerobic physical activity is 150 minutes a week of moderate-intensity physical activity or 75 minutes a week of vigorous-intensity exercise (43).
A range of exercise intensities have been used in research on depression, with most studies using a moderate or self-selected pace. Moderate-intensity physical activity is comparable to brisk walking, while vigorous-intensity exercise includes jogging or running. For individuals with depression, a more moderate pace may seem less daunting, especially for those not used to exercise. If you are physically active at a moderate pace, the exercise will feel "somewhat hard" and you will notice a slight increase in breathing and heart rate. However, the pace will seem easy enough that you could continue for a while. Research suggests that moderate to high intensities, compared to lower intensities, are more effective at reducing depression (18). Remember, as your fitness increases, physical activity will be easier, and you will be able to work harder with less effort.
Calories burned during exercise, or energy expenditure, is another way to measure exercise dose. This method is most helpful for people who like to use exercise equipment like elliptical trainers, treadmills, or stationary bicycles. Smartphone apps can also help you calculate calories you burn during exercise. Expending about 1,000 calories per week has been shown to have beneficial health effects and provide mental and physical health benefits (5, 18).
Other considerations for exercise dose are frequency and duration. Most research on exercise and depression has used a traditional exercise format of three to four times per week for 30 to 45 minutes per session (52). However, benefits have been seen with a variety of exercise programs. Research has shown that exercising for a shorter duration but more frequently (five days per week) and for a longer duration less frequently (three days per week) both result in a reduction of depression symptoms and remission of depression (18). Thus, there are many effective options. Some people prefer doing longer-duration exercise a few days a week while others prefer performing shorter bouts more often. People who have trouble finding time for exercise may prefer to break their sessions into shorter 10- to 15-minute bouts over the course of the day (43). You may find that more frequent bouts are less intimidating while still helping to reduce stress, improve thinking, and energize you.
It is important for people with symptoms of depression who would like to begin exercise to gradually increase their physical activity level over a period of a few weeks until they reach an adequate dose. This helps one develop physical fitness, prevents frustration, and assists in planning and problem solving. While you may notice some improvement in mood when you first begin exercising, significant improvements in depression usually take several weeks, similarly to what is seen with pharmacotherapy and psychotherapy. Full relief of symptoms may take several months of consistent exercise.
Resistance Training
Although not as widely studied as aerobic exercise, resistance exercise or strength training has been shown to have beneficial effects with regard to reducing depression (50). General recommendations for strength training as outlined in chapter 6 are to do resistance exercises two to three days per week, including the major muscle groups of the chest, back, arms, shoulders, hips, legs, and core, performing two to three sets of each exercise for 8 to 12 repetitions (43). One study using resistance training as a depression intervention reported greater symptom reduction at higher intensity (80 percent one-repetition maximum [1RM]) compared to lower intensity (20 percent 1RM) in an exercise program of three days per week for eight weeks (51). Generally, studies using resistance training have included two to three sessions per week with a duration of approximately 45 to 60 minutes, similar to the time spent in aerobic exercise programs (50).
Yoga and Mindful Exercise
Yoga has a long history of improving mood, and most existing research, despite some limitations, supports improved mood with yoga practice. In addition, there is support for improvement in residual symptoms, such as anxiety, with yoga (12). For example, Sudarshan Kriya yoga, which consists of rhythmic breathing, has been assessed in individuals with both depression and dysthymia and compared to drug therapy or electroconvulsive therapy. Remission rates were comparable for individuals engaged in the yoga and those receiving drug therapy, although the remission rate was highest for the electroconvulsive therapy (25). Mindfulness techniques have been used in stress reduction programs for decades (34). Mindful Hatha yoga is a formal meditation technique composed of gentle stretching and strengthening exercises that are completed slowly, with awareness of breathing. Preliminary research supports reduction of depression and anxiety with Hatha yoga and meditation (57). Meditation, which is often incorporated into the practice of yoga but has been studied as a sole practice as well, has also been associated with improvements in mood and reduced anxiety (3). Tai chi is another form of mind–body exercise that incorporates a series of slowly performed martial arts movements with meditation and breathing. Tai chi has been found to reduce stress, anxiety, and depression and enhance well-being and self-efficacy (58). Thus, it may be helpful to include yoga or other mindful exercises in physical activity plans for mental health (12). However, these types of exercises have not been as widely studied and do not offer all of the benefits of traditional fitness-based physical activity.
As to types of exercise, you have a variety of options for mental health promotion, including aerobic, resistance, and mindful exercise. Although this topic is not as widely studied in relation to depression, you can also be active by playing sports and enjoying other lifestyle activities such as walking and gardening. Consider doing your physical activity at a moderate pace, and aim for 150 minutes per week. But doing any physical activity is better than none; you can start at a lower level and then work your way toward a healthy dose of exercise that fits with recommendations. It is often useful to have a fitness professional help you plan your exercise routine and provide supervision as you get started. Most of the studies on depression have given participants exercise treatment using supervised exercise programs or a combined program of supervised and home-based exercise. If you are concerned about depression or another health condition, it is important that you consult with your health care provider to ensure that your symptoms do not get worse and to receive advice about the safest, most appropriate type of exercise for you.
Building Behavioral Skills for Physical Activity
Being physically active can be challenging for anyone, but for individuals who struggle with depression, developing an exercise routine can be particularly difficult. Low motivation, lack of enjoyment, difficulty planning, and fatigue are real barriers to physical activity. However, simple behavioral strategies or skills can help you incorporate more physical activity into your daily life (9).
Set Yourself Up for Success
Use positive cues to help you be more active, and remove cues that cause you to be less active. Examples of positive cues are posted notes, athletic shoes placed in a highly visible location, and notes on your calendar. Activity trackers or phone apps can help track movement and provide information such as steps, distance, calories, and sleep in order to prompt and monitor activity levels.
Have a Goal
Although many options for physical activity can help you on your journey to physical and mental health, set goals that meet your needs, preferences, and schedule. Goals provide direction and motivation. Make sure you set small, short-term goals that are realistic. For someone with depression, motivation is likely to be a problem. A realistic goal such as walking for 15 minutes a day can help you get started. Make sure you don't try to set too many goals at once. Focus on one type of physical activity first; then you can try new activities as you reach your goals.
Reward Yourself, and Find Some Fun
Positive reinforcement helps you establish a behavior, especially when you don't feel like doing it. Rewards don't have to be big, but they are important to mark small steps toward success. Also, pairing physical activity with something you like such as listening to your favorite music, watching a television show, or spending time with a friend can help you find enjoyment in exercise.
Recruit Social Support
Social support is especially important because a lack of support is a risk factor for depression. Having social support has also been shown to help people adopt healthy habits such as physical activity. Support can come in many forms, including having someone with whom to be active, having someone who encourages you, or having someone who can help you with your physical activity plans. Having several different sources of social support is ideal.
Identify Resources
Creating or making use of an environment that supports your physical activity can help you be more active and reach your goals. Examples include community resources like parks, trails, and fitness centers; mobile apps and technology; and educational information such as DVDs, social media, and magazines. Many businesses and malls have courses mapped out to help promote activity and help you track how far you’ve walked.
Plan Ahead, and Stay Positive
Everyone experiences barriers to exercise and interruptions to exercise plans. If you prepare for times when physical activity is more difficult (e.g., travel, illness, holidays), you will be more likely to get back on track. Often people drop out when they experience lapses because they tend to think negatively ("I’m a failure" or "I blew it"). This is particularly true for someone who struggles with depression. Changing negative thoughts to positive ones can help prevent a slip from becoming a relapse into old habits of inactivity.
Depression is a very common disorder that can occur at any time throughout the lifespan, and it significantly affects daily functioning in many areas. A variety of treatments are available, including medication and psychotherapy, and communication with a health care provider is important to monitor depressive symptoms and other concurrent health conditions. Exercise can also be an effective intervention for depression, both as a stand alone treatment and when added to other therapy. Using behavioral strategies can help promote adherence to exercise and should be incorporated as a part of physical activity adoption and maintenance.