Working In: Exercise's Role in Mental Health

Exercise has the unique ability to elicit adaptations in both the body and mind. In the world of superfoods, fountains of youth and the like, are we overlooking the unmatched, comprehensive health benefits of regular physical activity? In this article, I will focus on the positive mental effects of exercise. The commonly reported mental disease states, depression and anxiety, will be the focus. This article is not intended to diagnose or treat any conditions.


According to the National Institute of Health (NIH), generalized anxiety disorder is characterized as "displaying excessive anxiety or worry, most days for at least 6 months, about a number of things such as personal health, work, social interactions, and everyday routine life circumstances." The Generalized Anxiety Disorder 7-Item Scale (GAD-7), a subjective questionnaire, is a commonly used diagnostic tool. Questionnaire items include inability to relax, worrying, restlessness, irritability and other commonly reported symptoms of generalized anxiety disorder.


According to the NIH, depression is one of the most common mental disorders in the U.S. A multifaceted disorder, genetic, biological, environmental and other factors likely contribute to the wide variety of symptoms. Understood as a "mood disorder," depression can affect how you feel, think and act. Diagnosis is made following a minimum of two weeks with depressive symptoms. The Patient Health Questionnaire-9 (PHQ-9) is commonly used to diagnose. Loss of interest, increased fatigue, and hopelessness are among the many potential manifesting symptoms of depression.

Prevalence of Anxiety & Depression:

According to the World Health Organization's (WHO) report, “Depression and Other Common Mental Disorders: Global Health Estimates,” 4.4% of the global population is currently living with depression (322 million people) making depression the leading cause of disability worldwide. Depression is believed to be a multifaceted disorder including social, psychological and biological factors. (1) Depression is a highly complex, yet enormously important public health issue. Depression is predicted to be the second highest global burden of disease measured by number of years lost due to poor health, following a recent 20% prevalence increase. Depression rates were significantly higher in women, countries with a medium human development index and with the use of self-reporting instruments. (2)

The origin or onset of depressive symptoms is also complex. Severe "stress triggers" are hypothesized to contribute to depression by altering the brain's function. Early life stress may be predictive of one's lifetime vulnerability or resistance to stressful events. (3) Sui et al. reported that "major depressive disorder (MDD) in children and adolescents is strongly associated with recurrent depression in adulthood; other mental disorders; and increased risk for suicidal ideation, attempts, and completion." (4) Among children whom are diagnosed with major depressive disorder (∼8%), "functional impairments in their performance at school or work, natural development, and interactions with their families and peers are typically seen." Screening for MDD is generally recommended between the ages of 12-18, with insufficient data to suggest efficacy in children ≤11 years of age. Additionally, genetic factors appear to heighten one's susceptibility to MDD and suicidal ideation (SI). Taylor et al. findings support that "an adequate dose of physical activity diminishes risk of MDD and SI imposed by a genetic predisposition." (5)

As diagnosis and onset/origin of depression can be a complex area, therupatic avenues can also be relatively complex. When turning to self-care therapeutic options, stress management & adaptation techniques are a low hanging fruit to ensure continual, personalized practice. As we will discuss in this article, research suggests that exercise can help manage anxiety and depression, but it is important to understand that exercise is an additional tool and not a replacement for other forms of care that may be needed.

Stress: Adaptation vs. Wear & Tear

Bruce McEwen, a pioneer in stress physiology research, coined the term "allostatic load." Investigating the direct impact of various stressors on proper brain function, McEwen mentions that stress and trauma appear to "mediate physiological and behavioral responses." Strong emotions, particularly fear, appear to be the main driver(s) of these responses. McEwen further reinforces this belief, stating "stress is known to precipitate and exacerbate mood disorders including atrophy, hyperactivity and structural changes." (9)

McEwen's work details the multiple mechanisms responsible for positive stress adaptation. This adaptation is referred to as "allostasis" or "stability through change." Allostatic load is identified as the frequent, chronic or overstimulation of the allostatic systems. In normal circumstances, the adaptive systems effectively react to cope with stressors and "turn off" afterward. The trouble arises when allostatic load exceeds one's ability to adapt or overcome stressful events...known as the "price of adaptation." (12)

Types of allostatic load include:

(1) Frequent activation

(2) Failure to "shut off" after stressor

(3) Inadequate response/elevated activity of counter-regulations post stress

The key concept of allostatic load can be applied to various stressors, with an awareness of the dose dependent effects. Rather than stress avoidance, it is important to note that "stress promotes adaptation, but prolonged stress leads over time to wear-and-tear on the body." The key balance is between short-term stress eliciting adaptation versus chronic stress creating long-term damage. Numerous health detriments are a results of exceeding allostatic load and are seen in major depressive illness and chronic anxiety disorders. (10) Therefore, allostatic load, when incorporated as part of a comprehensive assessment may add additional insight into overall health. (11)

Beneficial self-care aspects of exercise:

Runners only "high"?

The "runner's high" is something most of you have heard of and some have experienced. What exactly is happening that results in this exercised-induced natural high? The commonly held belief of endogenous endorphin release has since been further investigated, uncovering the role of an additional system at play. The "runner's high" which may be explained in general terms as a combination of heightened mood, general relaxation and suppressed levels of pain, is largely due to the body's endocannabinoid system (ECS). The euphoric and analgesic effects largely depend on intact cannabinoid receptor 1 (CB1) receptors as well as peripheral CB1 and CB2 receptors. (13)

Aligning with McEwen's findings that strong emotions and stress "precipitate and exacerbate mood disorders," a bidirectional relationship between the ECS and anxiety and fear is becoming more apparent. The ECS possesses a "unique regulatory capacity for maintaining emotional homeostasis." In addition to the ECS's regulatory capacity, it has also been suggested that a properly functioning ECS serves as a "regulatory buffer system for emotional responses." (14) How then do you utilize this innate system to your advantage?

Exercise and the Endocannabinoid System (ECS):

Dr. Cecilia J Hillard, PhD is the director of the neuroscience research center at the medical college of Wisconsin. I had the opportunity to hear Dr. Hillard speak at the annual ACSM conference in Orlando, Florida in 2019. The topic of Dr. Hillard's presentation was on the effects of exercise on the ednocannabinoid system (ECS). If interested in a detailed breakdown of the ECS, it can be found in my previously article here.

The overarching theme of Dr. Hillard's presentation was various ways to activate the body's endogenous cannabinoid receptors. The most innate, proven method to do this is through.... exercise! Below is a breakdown of the ECS role taken directly from the presentation slide.

Brief overview:

The ECS acts on two cannabinoid receptors within the human body, CB1 and CB2. These receptors are termed G protein-coupled receptors (GPCRs). Varying in their location, CB1 receptors are abundant within the CNS (also the liver and adipose) while CB2 are primarily abundant within the immune system and brain microglia.

Key Takeaways:

  • Exercise increases ECS, via enhanced ligand concentrations and increased CB1R density in multiple brain regions.

  • There appears to be a down-regulatory effect on the ECS with chronic exercise.

  • The ECS contributes to exercise-induced effects on pain perception and anxiety; and the rewarding effects of exercise

Dose Dependent: Finding your ideal routine

Remembering the FITT principles:

(F: Frequency, I: Intensity, T: Time, T: Type)

In my previous article "The Best Fitness Program: The One You Keep Doing" (visit here) I discussed the importance of exercise adherence and how to prioritize the big ticket items without getting lost in the weeds. When structuring an exercise routine while prioritizing the mental benefits, there are two areas worth giving a bit more attention to....F: Frequency & T: Type.

F: Frequency

Lynette et al. investigated the positive mood effects of exercise, independent of fitness gains. Results suggest that one should focus on frequency of exercise rather than duration or intensity. This likely has a very logical explanation, that being a more frequent natural "feel good" throughout the week compared to a less frequent, supposing a minimal, but not excessive, threshold is met. (6) In addition to the acute benefits of exer