Scientists have known for a long time that keeping active is good for your physical health. It reduces the risk of heart disease, stroke, cancer, and other illnesses.
More recently, scientists have also spotted links between being active and a reduced risk of mental health symptoms.
In this feature, we'll dig into this relationship and ask how exercise might ease mental health conditions.
Exercise and mental health
Several large studies have investigated whether physical activity is related to mental health risk.
For instance, one study included more than 611,000 people. The authors concluded that “Levels of physical activity [...] were linked to reduced odds for major depression.”
Another study used data from 1.2 million people. Similarly, the researchers concluded that all types of physical activity were associated with reduced mental health symptoms, compared with no exercise.
By now, the fact that these two things are related is clear.
But researchers are still trying to figure out whether the relationship is causal: Does exercise directly cause a reduced mental health risk?
As an example, symptoms of depression may make people less likely to exercise. In this case, you could argue that depression causes a lack of exercise.
And there is growing evidence of a causal relationship between physical exercise and reduced mental health risk.
But everyone experiences mental health conditions in different ways. And everyone’s body responds differently to exercise.
So, it’s likely to be a complex relationship that varies from person to person. Perhaps it’s causal for some people but not for others.
Why the link?
Although evidence of a relationship between activity and mental health is piling up, scientists are still trying to figure out why this link exists.
And they have a few ideas. Below, we’ll outline some psychological and biological explanations.
It’s worth noting that all or none of these theories might be true. And some might be true for certain people but not others. Overall, researchers still have a lot to unpack.
Here, we’ll mainly focus on depression and anxiety, as scientists have investigated these conditions the most.
Let’s start with psychological mechanisms.
Exercise and fitness can have a wide range of effects on your psychology and how you feel about yourself.
Below, we’ll investigate the potential roles of self-esteem, social support, and self-belief.
Self-esteem can be described as having a sense of self-worth and a positive self-image. People living with depression and anxiety tend to have lower levels of self-esteem.
How you view your body is one component. For instance, one study found that women with more negative perceptions of their bodies are more likely to experience depressive symptoms.
There’s evidence that boosting physical self-perception is linked to improved overall self-esteem and reduced depression and anxiety in people with these conditions.
There's a lack of research directly investigating links between self-esteem, exercise, and mental health, but some studies provide hints.
For instance, research suggests that exercise can improve your body image, even without any measurable changes to your body.
Other studies have also shown that physical activity is linked to overall improved self-esteem.
So, it’s possible that these shifts in self-perception could reduce mental health risk or improve symptoms.
The small number of relevant studies hint that changes in self-esteem are an important factor.
But we need more research to uncover the full role of improved self-esteem in the mental health-boosting effects of exercise.
According to a review, people with depression who lack social support are more likely to have “worse outcomes, in terms of symptoms, recovery, and social functioning.”
And although there’s been less research, it seems to be a similar story for folks with anxiety disorders, bipolar disorder, or schizophrenia.
Exercise might provide more opportunities to interact with people. This could increase your chances of building relationships and developing better social support.
A study that included data from more than 40,000 people found that those who exercised frequently in their leisure time were less likely to experience depression symptoms. This, we might have expected.
But the scientists also found that when they accounted for the number of friends and social activities an individual had, a lot of the beneficial effect disappeared.
In other words, social support and social engagement explained a large part of the effect.
So, social support isn’t the whole story, but it seems to play an important role.
A meta-analysis of 20 studies concluded that physical activity helped increase levels of self-belief.
The theory goes that if exercise increases self-confidence, this confidence might flow into other aspects of your psychology and help relieve symptoms of depression.
However, little research has looked into this possible effect.
OK, now let’s move on to biological mechanisms.
When you exercise, a lot is going on in your body. Scientists think that these changes could help explain how physical activity protects your mental health.
We’ll cover three of these theories.
Brain plasticity, also called neuroplasticity, describes how the networks in your brain adapt and reorganize themselves in response to stimuli.
Although neuroplasticity is at its peak during childhood, it occurs throughout adulthood — for instance, when you're learning a new skill.
And there’s some evidence that neuroplasticity is “disrupted” in people with depression and anxiety.
Some of these growth factors, like brain-derived neurotrophic factor (BDNF), support the survival of nerve cells, their growth, and plasticity in the brain.
And some studies have found that levels of BDNF are lower in people experiencing depression.
So, perhaps exercise benefits mental health by boosting the release of growth factors.
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Scientists have found that the brains of people with depression sometimes have measurable differences.
For example, certain regions are smaller than those in people without depression — particularly the hippocampus. This plastic, vulnerable brain region is important for memory, learning, navigation, emotional behavior, and other functions.
Meanwhile, exercise is associated with increased volume of some brain regions, including the hippocampus.
Other scientists have shown that people who either got fit or maintained good fitness during a 12-year study had larger hippocampi than those who didn’t.
They also found that people whose anxiety worsened during the study were likelier to have smaller hippocampi.
Plus, increasing fitness was associated with a larger overall brain volume.
Experts don’t know the precise role of brain volume in our mental health, but this is another way that exercise might help.
Exercise and inflammation
And, as you may have guessed, exercise appears to help reduce inflammation.
According to a review, this anti-inflammatory action starts while you exercise and lasts for hours afterward.
If exercise is repeated, it also leads to long-term changes that reduce inflammation more generally. The review's authors write:
“Exercise can stimulate physiological changes that help to create a lasting anti-inflammatory environment.”
However, studies haven’t always confirmed the potential benefits for people with depression.
In one small study, for instance, the team found that exercise did reduce some markers of inflammation in people with depression, but their symptoms didn’t improve significantly.
The authors explain that “Inflammation may neither be necessary nor sufficient to induce or sustain depression in general.”
In other words, inflammation might not play a huge part in depression for everyone.
But, as the scientists explain, inflammation might play a significant role for some people. And for these individuals, exercise might be particularly useful.
Plenty more ideas
These aren’t the only theories about how exercise might improve our mental health, but they give you a taster.
Exercise also triggers the release of serotonin, which has an antidepressant effect, and endorphins, which reduce pain.
Plus, physical activity affects how your body regulates the primary stress hormone: cortisol.
It’s worth repeating that all, some, or none of these mechanisms might be at work in each of us. We’re all different, after all.
What should you do?
Physical activity is an excellent way to support overall health and reduce the risk of many chronic conditions.
And there’s now pretty good evidence of links between staying active and reducing the risk of mental health conditions.
Scientists are still trying to figure out exactly how the relationship between exercise and mental health works.
It may involve boosting your self-esteem and self-belief, increasing opportunities for social support, increasing brain plasticity and brain volume, and reducing inflammation.
If you don’t move around very much, gradually upping your activity is sure to improve your physical health and likely to improve your mental health.
And you don’t have to run 50 miles every day to benefit. Instead, start small — maybe 10 minutes of yoga or a walk around the block — and build up from there.
Don’t push yourself too hard, and try to find something you enjoy doing.
Aerobic exercise increases hippocampal subfield volumes in younger adults and prevents volume decline in the elderly. Brain Imaging & Behavior. (2019). https://link.springer.com/article/10.1007/s11682-019-00088-6
An 8-week randomized controlled trial on the effects of brisk walking, and brisk walking with abdominal electrical muscle stimulation on anthropometric, body composition, and self-perception measures in sedentary adult women. Psychology of Sport and Exercise. (2008). https://www.sciencedirect.com/science/article/pii/S1469029206000495
Anxiety disorders and inflammation in a large adult cohort. Translational Psychiatry. (2013). https://www.nature.com/articles/tp201327
Assessment of bidirectional relationships between physical activity and depression among adults. JAMA Psychiatry. (2019). https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2720689
Association between physical exercise and mental health in 1.2 million individuals in the USA between 2011 and 2015: A cross-sectional study. The Lancet Psychiatry. (2018). https://www.sciencedirect.com/science/article/pii/S221503661830227X
Associations between loneliness and perceived social support and outcomes of mental health problems: A systematic review. BMC Psychiatry. (2018). https://bmcpsychiatry.biomedcentral.com/articles/10.1186/s12888-018-1736-5
Associations of changes in cardiorespiratory fitness and symptoms of anxiety and depression with brain volumes: The HUNT Study. Frontiers in Behavioral Neuroscience. (2019). https://www.frontiersin.org/articles/10.3389/fnbeh.2019.00053/full
Body image satisfaction and depression in midlife women: The Study of Women’s Health Across the Nation (SWAN). Archives of Women’s Mental Health. (2014). https://link.springer.com/article/10.1007/s00737-014-0416-9
Brain grey matter abnormalities in medication-free patients with major depressive disorder: A meta-analysis. Psychological Medicine. (2014). https://www.cambridge.org/core/journals/psychological-medicine/article/brain-grey-matter-abnormalities-in-medicationfree-patients-with-major-depressive-disorder-a-metaanalysis/4EF21A13A69148E61BFBA4D33801B5CD
Bridging animal and human models of exercise-induced brain plasticity. Trends in Cognitive Sciences. (2013). https://www.sciencedirect.com/science/article/pii/S1364661313001666
Comparison of changes in physical self-concept, global self-esteem, depression and anxiety following two different psychomotor therapy programs in nonpsychotic psychiatric inpatients. Psychotherapy and Psychosomatics. (2005). https://karger.com/pps/article-abstract/74/6/353/282243/Comparison-of-Changes-in-Physical-Self-Concept?redirectedFrom=fulltext
Discovery and replication of cerebral blood flow differences in major depressive disorder. Molecular Psychiatry. (2019). https://www.nature.com/articles/s41380-019-0464-7
Effects of different exercise conditions on antioxidant potential and mental assessment. Sports. (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8001181/
Effects of exercise on physical self-concept, global self-esteem, and depression in women of low socioeconomic status with elevated depressive symptoms. Journal of Sport & Exercise Psychology. (2014). https://pubmed.ncbi.nlm.nih.gov/25226604/
Exercise and Inflammation. Best Practice & Research Clinical Rheumatology. (2020). https://www.sciencedirect.com/science/article/pii/S1521694220300218
Exercise-induced neuroplasticity: A mechanistic model and prospects for promoting plasticity. The Neuroscientist. (2018). https://journals.sagepub.com/doi/10.1177/1073858418771538
Hippocampus in health and disease: An overview. Annals of Indian Academy of Neurology. (2012). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548359/
Immunological effects of behavioral activation with exercise in major depression: An exploratory randomized controlled trial. Nature. (2017). https://www.nature.com/articles/tp201776
Inflammation and its discontents: The role of cytokines in the pathophysiology of major depression. Biological Psychiatry. (2009). https://www.sciencedirect.com/science/article/pii/S0006322308015321
Interactive effects of fitness and hormone treatment on brain health in postmenopausal women. Neurobiology of Aging. (2007). https://www.sciencedirect.com/science/article/pii/S0197458005004215
Mechanisms underpinning the association between physical activity and mental health in adolescence: A 6-year study. International Journal of Behavioral Nutrition and Physical Activity. (2020). https://link.springer.com/article/10.1186/s12966-020-0911-5
Number of years of team and individual sport participation during adolescence and depressive symptoms in early adulthood. Human Kinetics Journal. (2015). https://journals.humankinetics.com/view/journals/jsep/38/1/article-p105.xml
Physical activity and common mental disorders. BJPsych. (2018). https://www.cambridge.org/core/journals/the-british-journal-of-psychiatry/article/physical-activity-and-common-mental-disorders/267C0AD202EBE8170BA0A5AE4E7446A6
Physical activity and depression: Towards understanding the antidepressant mechanisms of physical activity. Neuroscience & Biobehavioral Reviews. (2019). https://www.sciencedirect.com/science/article/pii/S0149763419305640
Physical activity and self-esteem: Testing direct and indirect relationships associated with psychological and physical mechanisms. Neurosychiatric Disease and Treatment. (2016). https://www.tandfonline.com/doi/full/10.2147/NDT.S116811
Physical activity interventions differentially affect exercise task and barrier self-efficacy: A meta-analysis. Health Psychology. (2014). https://psycnet.apa.org/doiLanding?doi=10.1037%2Fa0033864
Regulation of cerebral blood flow during exercise. Sports Medicine. (2007). https://pubmed.ncbi.nlm.nih.gov/17722948/
Relationship between self-efficacy and symptoms of anxiety, depression, worry and social avoidance in a normal sample of students. Iranian Journal of Psychiatry and Behavioral Sciences. (2011). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3939966/
Review: Low self-esteem and internalizing disorders in young people — a systematic review. Child and Adolescent Mental Health. (2016). https://acamh.onlinelibrary.wiley.com/doi/abs/10.1111/camh.12204
Serum BDNF concentrations as peripheral manifestations of depression: Evidence from a systematic review and meta-analyses on 179 associations (N=9484). Molecular Psychiatry. (2015). https://www.nature.com/articles/mp2013105
Stress, depression, and neuroplasticity: A convergence of mechanisms. Neuropsychopharmacology. (2007). https://www.nature.com/articles/1301574
Subcortical brain alterations in major depressive disorder: Findings from the ENIGMA Major Depressive Disorder working group. Nature. (2015). https://www.nature.com/articles/mp201569
Testing causality in the association between regular exercise and symptoms of anxiety and depression. JAMA Psychiatry. (2008). https://jamanetwork.com/journals/jamapsychiatry/article-abstract/210112
The prospective associations between self-efficacy and depressive symptoms from early to middle adolescence: A cross-lagged model. Journal of Youth and Adolescence. (2017). https://link.springer.com/article/10.1007/s10964-016-0614-z