Depression is a common and debilitating mental health disorder that affects millions of people worldwide. It can impact any aspect of an individual’s life. Epidemiological studies show that depression is a significant cause of morbidity and mortality worldwide. Depression is not only characterized by persistent feelings of sadness and hopelessness. The distinctive feature of depression is the loss of interest and pleasure in activities. Depressed people seem to “shut down”. While there are many ways into depression, there are also many ways out. Besides psychotherapy and medication, physical activity can play an important role in managing and even alleviating symptoms of depression.
The Biological Mechanisms
Biological mechanisms underpinning the positive effects of physical activity on depression are not fully clarified yet. There are, however, some hypotheses based on the current research:
Endorphin Release
Often dubbed the body’s “natural painkillers,” endorphins are released during intense physical activity, like exercising. These chemicals act in our body as analgesics, reducing the perception of pain and simultaneously producing a feeling of euphoria, often referred to as the “runner’s high.”
Serotonin
Serotonin is often called the “feel-good” neurotransmitter (a chemical that helps transmit signals in the brain). It plays a crucial role in regulating mood, appetite, sleep, memory, and learning. The role of serotonin in depression has been a major research focus for several decades now.
One of the prevailing theories about the biological basis of depression is that it’s associated with a serotonin deficiency. It does not mean that a low serotonin level causes depression. It means that when people get depressed, serotonin goes down, and its deficit maintains depressive symptoms. This theory is supported by the fact that many antidepressant medications, such as selective serotonin reuptake inhibitors (SSRIs) like Prozac, increase serotonin levels in the brain with a positive impact on recovery.
Physical activity has been shown to increase the availability of tryptophan, a precursor to serotonin, in the brain. This can increase serotonin production and release, working like a “natural antidepressant” – without taking pills and without side effects.
Neuroplasticity
Exercise increases the production of BDNF, a protein that supports the survival of existing neurons and stimulates the growth of new neurons and synapses. Higher BDNF levels are associated with better cognitive functioning. Physical activity has been shown to promote the formation of new neurons in the hippocampus, a brain region linked to mood and memory. This finding is interesting in light of research showing that the hippocampus can shrink in people with depression. Thus, physical exercise seems to reverse this degenerative process.
Reduction of Inflammation
Chronic inflammation has also been linked to depression. Physical activity, especially regular aerobic exercise, can reduce levels of pro-inflammatory cytokines, proteins that promote inflammation. It is possible that the anti-inflammatory effect of exercise indirectly reduces depressive symptoms.
Hormonal Regulation
Physical activity can regulate the balance of certain hormones that influence mood and stress. Regular exercise can, among others, normalize cortisol levels. Cortisol is often called the “stress hormone,” as elevated cortisol levels are associated with chronic stress. Physical activity also improves insulin sensitivity, which can stabilize blood sugar levels. Fluctuations in blood sugar influence mood and energy.
The Psychosocial Mechanisms
Exercise may help fight depression not only through biological processes. The psychosocial mechanisms involved in physical activity are equally important. Here are some of the psychosocial aspects of physical training:
Enhanced Self-Esteem and Self-Efficacy
Engaging in regular physical activity leads to improvements in physical appearance and capabilities. This can boost self-esteem (self-worth) and, subsequently, the belief in one’s ability to achieve goals (self-efficacy).
Mastery and Achievement
Setting and achieving fitness goals can provide a sense of accomplishment and mastery. Mastery is a feeling that one has control over one’s environment (and body) and can effectively handle challenges. The belief in one’s ability to overcome challenges is an important part of resilience. On the other hand, achievement means accomplishing goals or tasks. As individuals achieve more and experience success, they are motivated to set new goals. This leads to a positive feedback loop of achievement, self-efficacy, resilience and improved mood.
Social Interaction
Group exercises, team sports, or even just being around others at a gym can provide opportunities for social interactions and by that, reduce feelings of isolation and loneliness. Humans are inherently social beings. We have evolved to live in communities and rely on one another for physical and emotional survival. Being in a social network provides us with a sense of responsibility and purpose. Positive social interactions lead to the release of oxytocin, a hormone that helps regulate stress and anxiety levels. Additionally, engaging in enjoyable social activities provides a sense of normalcy.
Structured Routine
Regular physical activity enforces better structure to one’s day, which can be especially beneficial for people suffering from depression. They often struggle with a lack of routine or purpose – which is a part of the typical depressive symptom picture.
Enhanced Cognitive Function
Physical activity, as mentioned above, improves cognitive function, which is essential in problem-solving and decision-making. This helps individuals navigate life challenges more effectively and contributes to psychological resilience.
Take away message
Depression is a complex, multifaceted condition. It is influenced by a combination of biological, psychological, and social mechanisms. Its causes and manifestations can vary widely among individuals but the decrease of interest in activities is common. The most efficient clinical interventions address both the biological and psychosocial aspects of depression. Physical activity may be used either as an important ingredient of a bio-psycho-social treatment package or as a stand-alone treatment. In can play a pivotal role in recovery.
It’s essential to choose a physical activity that one enjoys to ensure sustainability. To maintain motivation, start with small, achievable goals and gradually increase the intensity and duration. Remember that what is too much for someone may be too little for others – one seize does not fit all when it comes to exercise.
Suggested readings
Blumenthal, J. A., Babyak, M. A., Moore, K. A., et al. (1999). Effects of exercise training on older patients with major depression. Archives of Internal Medicine, 159(19), 2349-2356.
Craft, L. L., & Perna, F. M. (2004). The benefits of exercise for the clinically depressed. Primary Care Companion to The Journal of Clinical Psychiatry, 6(3), 104-111.
Dinas, P. C., Koutedakis, Y., & Flouris, A. D. (2011). Effects of exercise and physical activity on depression. Irish Journal of Medical Science, 180(2), 319-325.
Schuch, F. B., Vancampfort, D., Firth, J., et al. (2018). Physical Activity and Incident Depression: A Meta-Analysis of Prospective Cohort Studies. American Journal of Psychiatry, 175(7), 631-648.
Cooney, G. M., Dwan, K., Greig, C. A., et al. (2013). Exercise for depression. Cochrane Database of Systematic Reviews, (9).
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