15.4: Exercise and Physical Activity in the Treatment of Depression

Initial research on exercise as a treatment for depression was conducted in the 1980s and 1990s. These findings were first summarized in a quantitative review by North and colleagues (1990) who found that exercise alleviated depressive symptoms and demonstrated comparable effectiveness—and at times increased effectiveness—to traditional treatments (e.g., antidepressant drugs and psychotherapy). A major limitation of their review was the heterogeneous composition of the patient samples. That is, the review included both nonclinical and clinical samples. Nonetheless, this meta-analysis was the first to quantitatively demonstrate the potential benefits of exercise for reducing depressive symptoms and laid the foundation for growing interest in exercise as a treatment for depression.

In the following sections, we outline the evidence examining exercise as a treatment for depression and document the potential utility for exercise to be used either as a stand-alone or complementary intervention to existing depression treatments. To date, research has examined the effects of exercise on depression using short- (acute) and long-term (chronic) interventions. Acute interventions have focused primarily on providing short-term relief of specific symptoms, such as elevating low mood. Chronic interventions have assessed whether exercise can be used to effectively treat or resolve depression (i.e., the disorder) and reduce total depressive symptom severity. Below, we discuss the evidence related to both types of exercise interventions and their role in the treatment of depression.

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15.4.1. The Role of Acute Exercise in the Treatment of Depression

Acute (single bouts) exercise will not necessarily resolve an individual’s depressive symptoms, but it has well-characterized effects on regulating mood and has the potential to manage symptoms associated with depression. For example, Yeung (1996) reviewed the effects of acute exercise on mood from studies conducted between the years of 1976 and 1995 and found support for acute exercise-induced mood benefits among normative, healthy samples. In 2005, Bartholomew et al. were interested in determining whether these acute exercise-induced mood benefits could generalize to clinical samples. Using a mixed within-between subjects experimental design, the authors examined the impact of a single bout of aerobic exercise on mood and psychological well-being among 40 adults diagnosed with MDD (M_age = 38.1 years; range = 18–55; 25 female). Twenty participants completed a 30-min bout of moderate-intensity brisk walking, while the other 20 participants completed a seated rest control condition. Mood and well-being measures were assessed at four separate time points: before the condition (i.e., baseline), 10-min post, 30-min post, and 60-min post. Compared to the control condition, moderate-intensity exercise improved psychological well-being and the mood state of vigor at all postcondition assessments.

Meyer, Koltyn, and colleagues (2016a) examined the impact of acute exercise on mood in a sample of 24 females diagnosed with MDD (M_age = 38.6 years; SD = 14.0). The authors were interested in determining whether postexercise mood improvements were influenced by exercise intensity prescription. In a within-subjects crossover design, participants performed three different exercise intensities and a seated rest control condition on separate days. Exercise intensities consisted of light, moderate, or hard and were performed at a rating of perceived exertion [RPE] of 11, 13, and 15, based on the original 6–20 RPE scale (Borg, 1998), respectively, while the control condition consisted of quiet rest on a stationary bicycle. Compared to the control condition, a single, 20-min bout of cycling, regardless of intensity, significantly improved depressed mood at 10-and 30-min following exercise cessation.

Meyer, Ellingson, et al. (2016) examined whether other exercise characteristics, such as a self-selected, preferred versus prescribed exercise intensity, would influence the postexercise mood effects. Using the same study sample as above, the authors had 24 females perform an additional 20-min bout of aerobic exercise at a self-selected, preferred intensity. Mood outcomes following the preferred exercise intensity were compared to the light, moderate, or hard intensity session that was closest in terms of RPE to the exercise they did during their preferred session (i.e., if the participants exercise at a low intensity during the preferred session, then their response to that session was compared with the response to the low-intensity during the prescribed session). Although the prescribed exercise session resulted in slightly favorable effects relative to the self-selected, preferred exercise bout, these effects were small and nonsignificant, highlighting that single bouts of aerobic exercise at any intensity may benefit depressed mood for up to 30-and 60-min postexercise.

Taken together, these findings support the idea that acute exercise can influence specific mood states (e.g., depressed mood and vigor),⁵ at least in the short-term, among individuals with MDD. Given that one of the core criterion symptoms of MDD is low or depressed mood, acute exercise may be particularly effective for managing these core symptoms. Additional research has shown that acute exercise impacts other disrupted psychological processes in depression. Acute aerobic exercise can attenuate self-reported negative affect among individuals who recovered from MDD (Mata et al., 2013). Separate studies have shown that acute aerobic exercise can diminish reactivity to sad stimuli (Brush, Olson, et al., 2020) and enhance positive emotional reactivity processes (Brush, Foti, et al., 2020) among adults at risk for developing MDD (i.e., those high in depressive symptoms), respectively. Therefore, the utility of acute exercise in the treatment of depression may be most evident in the management of symptoms and psychological processes commonly disrupted in depression. Acute exercise may be most effective in managing symptoms of depression while other treatments and their effects can manifest, which can take weeks to months (e.g., Knubben et al., 2007; Legrand & Neff, 2016).

Several questions remain in the acute exercise-depression relationship. The time-course of the postexercise mood benefits are not clear. The Bartholomew et al. and the Meyer et al. studies documented benefits anywhere from 30-60 min postexercise, however, whether the effects are sustained beyond 1 hr is unknown. Studies have primarily assessed aerobic forms of exercise performed for approximately 20-30 min. Research is needed to determine how long the postexercise benefits last, whether they relate to clinical outcomes (e.g., depressive symptom reduction), and whether other exercise characteristics (e.g., modality and dose) impact the effects of acute exercise on mood among individuals with clinical depression. Further, it is unknown how acute exercise compares to other brief interventions (e.g., brief behavioral activation treatment for depression [BATD]; Gawrysiak et al., 2009; Lejuez et al., 2001, 2011) in managing symptoms of depression. Research that addresses these items can help “push the envelope” for the role of acute exercise in the treatment and management of depression.

15.4.2. The Role of Chronic Exercise in the Treatment of Depression

There is a long history of research examining the effects of chronic (longer-term) exercise on depression. Numerous RCTs have examined the effects of exercise for individuals with elevated depressive symptoms. There has also been an accompanying rise in the number of meta-analyses and systematic reviews on this topic (e.g., Cooney et al., 2013; Ekkekakis, 2015; Schuch, Vancampfort, et al., 2016).

In one of the most widely cited and influential RCTs, James Blumenthal and colleagues (1999)randomized 156 men and women with MDD (aged 50 years and older) to one of three conditions: (a) an aerobic exercise training program, (b) standard antidepressant treatment with sertraline (i.e., SSRI drug), or (c) combined exercise plus sertraline treatment. For the aerobic exercise training program, three, supervised sessions per week were performed over a span of 16 consecutive weeks in a group setting. Participants were prescribed walking or jogging at a vigorous exercise intensity that ranged from 70–85% of an individual’s heart rate reserve (HRR).⁶ Although participants assigned to the sertraline treatment alone experienced a more rapid initial antidepressant response, there were no significant differences in depressive symptom reduction between groups by the end of the 16-week trial, indicating that each treatment resulted in similar-sized reductions in depressive symptoms. Of the 156 patients who entered the trial, 60.4% of patients in the aerobic exercise training program, 68.8% of patients in the sertraline treatment condition, and 65.5% of patients in the combined exercise and sertraline treatment no longer met criteria for a DSM-IV⁷-defined diagnosis of MDD post-treatment.

The authors examined long-term outcomes following each of the three treatments in a subsequent study that followed these same patients six months post-intervention. At the follow-up visit,participants assigned to the aerobic exercise group displayed significantly lower rates of depression (~30%) compared to the other two treatment groups (sertraline: 52%; combined exercise plus sertraline: 55%; Babyak et al., 2000). At the time that this study was published and to the present day, this finding has been critically important in providing some of the strongest evidence for aerobic exercise as both a stand-alone and complementary treatment to standard antidepressant drugs. Notably, the aerobic exercise treatment group experienced lower relapse compared to participants in the other two treatment groups that included antidepressant drugs, providing the first evidence for the use of aerobic exercise to resolve depression over the long-term (6 months following the end of treatment). A limitation of this study was the lack of a placebo control group, which does not permit conclusions about the specific effects of each treatment arm. Therefore, Blumenthal and colleagues (2007) performed a follow-up investigation that added a placebo group to their previous study design. In this study, 202 participants (~76% female)diagnosed with MDD were randomized to the following groups for 16 consecutive weeks: (a) home-based aerobic exercise, (b) supervised exercise in a group setting, (c) sertraline, or (d) a placebo pill. After treatment, 41% of the participants achieved remission and all active treatment groups tended to have greater remission rates compared to the placebo pill group (home-based aerobic exercise: 40%; supervised exercise in a group setting: 45%; sertraline: 47%; and placebo pill: 31%). These studies have helped establish preliminary support for the efficacy of exercise treatment for MDD.

There has been a longstanding interest in determining the presence of a dose-response relationship between exercise and reductions in depressive symptoms (Rethorst & Trivedi, 2013). In 2000, a scientific symposium sponsored by Health Canada and the U.S. Centers for Disease Control and Prevention was held to determine whether a dose-response relationship exists between physical activity and multiple health-related outcomes, including depression. At the time, experts indicated that aerobic exercise programs lasting at least 6–12 weeks were consistently associated with depressive symptom reductions comparable in magnitude to those observed following antidepressant drug treatment; however, they noted that there was insufficient evidence to make definitive conclusions regarding a dose-response relationship between exercise and depression.

Dunn et al. (2005) conducted the first RCT designed specifically to assess the dose-response relationship of exercise for depression. Dunn et al. randomized 80 patients with mild-to-moderate depression severity to two different doses of aerobic exercise (7 kcal/kg/week, low dose [LD] or 17.5 kcal/kg/week, public health dose [PHD]) performed at two different frequencies (three or five days per week) or to an attention-controlled placebo group of flexibility training. Exercise intensity was self-selected by participants assigned to the exercise conditions. There was a significant dose-response effect. A greater depressive symptom reduction (47% decrease in HRSD score) was observed patients in the PHD group compared to the LD (30% decrease in HRSD score) and stretching control groups (29% decrease in HRSD score). Further, the treatment response following the PHD prescription was comparable to depressive symptom reductions that are typically observed following other depression treatments, including antidepressant drugs and CBT.

Additional evidence supporting a dose-response relationship was examined in a study examining the effects of a long-term exercise training program on depression among women (Chu et al., 2009). The authors randomized women with high levels of depressive symptoms to a low- or high-intensity aerobic exercise condition or to a stretching program for 10 weeks. Participants in the aerobic exercise groups met for one 30-40 min supervised session and then were asked to complete three-to-four additional unsupervised exercise sessions during the week. During the unsupervised sessions, participants in the exercise groups were permitted to choose their preferred mode of aerobic exercise, such as aerobic dancing, walking, or biking. This approach may have served to enhance motivation and adherence to exercise, since participants were afforded greater autonomy in their own exercise. All three groups demonstrated a significant reduction in depressive symptoms at the end of the 10-week intervention. After controlling for pre-treatment depressive symptoms (as measured by the BDI-II),depressive symptoms were significantly lower following the intervention for the high-intensity aerobic exercise group compared to the low-intensity and stretching groups, suggesting a potential dose-response effect that favors higher aerobic exercise intensity prescriptions for depressive symptom reduction.

Trivedi and colleagues (2011) extended these findings by showing that aerobic exercise training can also be effective as an augmentation or complementary treatment for patients with treatment-resistant depression. The authors enrolled patients who failed to achieve remission following at least six weeks of treatment with SSRIs and prescribed one of two 12-week exercise doses:to patients: a low dose (4 kcal/kg/week) or high dose (16 kcal/kg/week).⁸ Among 126 men and women, those assigned to the higher dose of exercise showed a trend for increased remission rates compared to participants who were assigned to the lower dose of exercise (28.3% for the high-dose group compared to 15.5% for the low-dose group). Higher doses of aerobic exercise may more effectively treat depression and be a viable augmentation strategy for patients with depression who have failed to respond to antidepressant drugs.

It is important to note that the authors found that those assigned to the lower exercise exhibited better adherence rates compared to those assigned to the higher dose. This suggests that lower doses of moderate-to-vigorous intensity aerobic exercise may be more tolerable and acceptable for individuals with depression aiming to begin an aerobic exercise program.

Most of the work on the effects of exercise as a treatment for depression has focused on the effectiveness of aerobic exercise. Indeed, a meta-analysis that aggregated findings across 25 RCTs (M_length= 10.29 weeks; range of RCT length = 3–32 weeks)⁹ indicated large reductions in depressive symptoms following exercise compared to nonactive interventions (Schuch, Vancampfort, et al., 2016). The extent to which other exercise modalities have utility in the treatment of depression has received less attention.

Resistance exercise training is known for its many health benefits, especially for increasing muscular strength, muscle mass, endurance, and/or power (U.S. Department of Health and Human Services, 2008). Research has also examined the potential antidepressant effects of resistance exercise training. Singh et al. (1997) assessed whether 10 weeks of resistance exercise training significantly reduced depression among 32 older adults over the age of 60 years (M_age = 71.3 years; SD = 1.2) with diagnosed major/minor depression or dysthymia.¹⁰ Intervention groups consisted of a supervised, high-intensity resistance exercise training program performed three times per week or an attention-control group. Participants in the resistance exercise group performed upper and lower body exercises for three sets of eight repetitions at 80% of an individual’s one-repetition maximum (1-RM).¹¹ Following the intervention, participants in the resistance exercise group reported a 59% reduction in depressive symptoms compared to a 26% reduction in the attention-control group. Participants were encouraged to continue their resistance exercise regimen at least twice weekly for another ten weeks upon completing the intervention. After this follow-up period, ~73% of the participants in the resistance exercise group achieved remission, while only ~36% of the attention-control participants achieved remission (Singh et al., 2001). This evidence served as preliminary support for the antidepressant effects of resistance exercise in both shorter and longer periods of time.

Similar to the aerobic exercise literature, Singh and colleagues were interested in examining potential dose-response effects of resistance exercise training on depressive symptoms. In a subsequent study, the authors randomly assigned 60 older adults between the ages of 60 and 85 to a high (80% of 1-RM), low (20% of 1-RM), or treatment-as-usual comparator condition for eight weeks (Singh et al., 2005). High-intensity resistance exercise training resulted in larger antidepressant effects compared to the low-intensity and treatment-as-usual comparator groups. Interestingly, the authors examined the proportion of individuals who adequately responded to treatment, which was defined as a 50% reduction in the HRSD score from pre-to-posttreatment. The results revealed a 61% response rate in the high-intensity group compared to 29% and 21% in the low-intensity and treatment-as-usual groups, respectively. This evidence suggests that resistance exercise training may not only reduce depression, but higher intensities may be more effective.

Noting that the majority of meta-analyses conducted on the exercise and depression relationship has focused on aerobic forms of exercise, Gordon and colleagues (2018) aimed to address this gap in the literature by performing the first quantitative review of the effects of resistance exercise training on depression. Gordon et al.’s meta-analysis combined effects from 33 RCTs, which included a total of 1,877 participants, and found that resistance exercise training resulted in a moderately-sized reduction in depressive symptoms, regardless of sociodemographic characteristics. It is important to note that this meta-analysis combined findings from studies that included both normative and clinical samples. When examining only those with clinical levels of depression (i.e., at least mild-to-moderate depressive symptoms), the resistance exercise training had even larger antidepressant effects compared to those with subclinical depression. There was no specific impact of type of resistance exercise training protocol on depression outcomes.

Collectively, the evidence generally supports the notion that both aerobic and resistance forms of exercise are effective treatments for depression. This has been shown in studies examining exercise training as a monotherapy or complementary treatment to other treatments, namely antidepressant drugs. The antidepressant effects of exercise are at least as comparable to antidepressant drug treatments and over the long run, there is evidence to suggest that exercise may result in more favorable reductions in depressive symptoms and disorders compared to antidepressant drugs (Babyak et al., 2000). It is important, however, for future studies to continue to examine the long-term impact of exercise on depression to fully understand how long effects are sustained. Most of the research to date has been conducted in adults with depression, while the impact of exercise training in other populations that are substantially impacted by depression, including children and adolescents, is less clear. Future studies are needed in other vulnerable populations to determine whether effects are generalizable.Overall, exercise should play an important role in the treatment of depression as a stand-alone and/or complementary treatment.

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Reference

⁵ In acute exercise studies, the Profile of Mood States (McNair et al., 1971) has been the primary instrument used to assess mood in the context of depression, which has its limitations. As highlighted by Ekkekakis and Zenko (2016), the POMS was not designed to capture the global construct of “mood”. Instead, it decomposes mood into six distinct states: (a) tension; (b) depression; (c) anger; (d) vigor; (e) fatigue; and (f) confusion. There are conceivably other mood states that are not being measured by the POMS; therefore, when interpreting studies that use the POMS, it is important to note which specific mood states are altered through exercise to draw valid and accurate inferences. Refer to Ekkekakis (2013) and Ekkekakis and Zenko (2016) for a discussion on problems associated with using the POMS in exercise psychology research.

⁶ HRR is computed as the difference between an individual’s maximal and resting HR.

⁷ The American Psychiatric Association periodically updates the DSM to reflect the most current and cutting-edge research literature on psychopathology. The most recent addition (i.e., DSM-5) was released in 2013. The first version of the DSM-IV was released in 1994.

⁸ The low dose prescription of 4 kcal/kg/week is equivalent to approximately 45 min of moderate-to-vigorous intensity exercise per week, while the high dose prescription is equivalent to approximately 180 min of moderate-to-vigorous intensity exercise per week.

⁹ One RCT included in the Schuch, Vancampfort, et al. (2016) meta-analysis did not report the trial length. Therefore, the mean and range of trial lengths reported include 24/25 RCTs that were included in the authors’ meta-analysis.

¹⁰ Dysthymia is no longer considered a diagnosis in the DSM-5. It was removed from the DSM-Fourth Edition (IV) and replaced by persistent depressive disorder. Minor depression was considered a Depressive Disorder Not Otherwise Specified in the DSM-IV.

¹¹ Resistance exercise training intensity is often based off an individual’s 1-RM, which is defined as the maximal amount of weight an individual can lift in a single repetition (Garber et al., 2011).