How does physical activity benefit mental health?

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.”

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. 

Here, we’ll mainly focus on depression and anxiety, as scientists have investigated these conditions the most.

Let’s start with psychological mechanisms.

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

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 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.

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. 

Social support

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. 

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.

Self-belief

Having low self-belief, or low confidence in your abilities, is linked to symptoms of depression and other mental health conditions.

A meta-analysis of 20 studies concluded that physical activity helped increase levels of self-belief.

However, little research has looked into this possible effect.

OK, now let’s move on to biological mechanisms.

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

Brain plasticity, also called neuroplasticity, describes how the networks in your brain adapt and reorganize themselves in response to stimuli. 

And there’s some evidence that neuroplasticity is “disrupted” in people with depression and anxiety.

Meanwhile, some experts believe that exercise can support neuroplasticity. And it may do this by promoting the release of growth factors.

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.

Brain size

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.

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

Scientists now think that long-term, low-level inflammation might play a role in certain mental health conditions, including depression and anxiety. 

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. 

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.”

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.

Other theories involve improved blood circulation in the brain, increased circulating antioxidants, and changes in your brain's hormone levels.

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.

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.