What Are the Mental Health Benefits of Exercise?

The Science of Exercise & Brain Chemistry

Exercise has quite an effect on our bodies. If you have ever felt the desire to punch the air and scream “I did it!” after a workout, you have experienced the brain chemistry that has occurred as a result. So what ingredients go into this “feel good brain soup?” Let’s start by discussing two categories: neurotransmitters and neuromodulators.

Neurotransmitters

The first ingredient would be our neurotransmitters. These are little chemical messengers that signal our brain and change the way we feel. There are several types of these couriers, but two  important ones: serotonin and dopamine.

Dopamine is the neurotransmitter involved in our reward and motivation system. It increases our drive to do things, and rewards us when we complete them. Serotonin, on the other hand, has been noted for its role in mood regulation, including its antidepressant effects.
Others include epinephrine, norepinephrine, GABA, and glutamate. And while these neurotransmitters each have different individual functions, they all seem to contribute to improving mood. Evidence shows that these neurotransmitters (and many others) are released during exercise and physical activity,¹ thus contributing to an increase in our positive affect.

Neuromodulators

Another ingredient that contributes to the feel-good brain soup that occurs after exercise is the neuromodulator family—these include two types called endorphins and endocannabinoids. Endorphins are endogenous opioids, which basically means that they bind to the same receptors as the opioids we are prescribed pharmacologically, but our body makes them inside of us. The pain-clearing effect they have is very similar.

The other category that we are learning is released during and after exercise is the group known as endocannabinoids. Having receptors in our brains that respond to these elements is what allows opioids and marijuana to have the effects on us that they do. But when we exercise, our body releases them for us, which means we get that good feeling without any of the potentially negative side effects we’d get from using drugs to release them.

Exercise & Depression

Depression is a clinical disorder where an intense feeling of sadness is present during the majority of time, as well as other serious symptoms which all have a negative impact on a person’s life. Clinical depression should be assessed and treated by a professional—exercise might be part of that treatment but that is up to the patient and the professional together. Research has shown that exercise combined with other treatments can have a positive effect on mental health and reduces depressive symptoms.

In a meta analysis, Dr. Vicki Conn of the University of Missouri reviewed and analyzed 60 studies, and found that physical activity reduced depressive symptoms in non-clinical populations.² These studies included situations that were both supervised by a professional and performed independently, and found that in both scenarios people saw improvement, meaning that there is a benefit in the physical activity itself, and not a hidden variable (like an awesome personal trainer) intervening.

This meta-analysis was later included in a larger systematic review of meta-analyses by Hu et al., which concluded that, based on their findings, exercise has an overall moderate effect on reducing depressive symptoms in the general population. This was found to be true across age groups, including children, adults, and the elderly—meaning physical activity is beneficial for every age.³

There is also evidence that physical activity is beneficial for the treatment of those diagnosed with clinical depression. A systematic review by the Cochrane Library found that, after reviewing 39 studies, exercise also had a moderate effect on depression. The authors warn that the actual effect might be smaller partly because it would be impossible to blind your participants during exercise, and thus bias may have been increased. However, with the data reviewed, there was a clear effect. One interesting finding was that there appeared to be a slightly better response from the resistance training trials than the aerobic. But for these conclusions to be more robust, more data are needed.

When it comes to exercise for depression, one aspect that should be mentioned is that it’s important to look at our comparison points. For example, in the review, exercise appeared to be as effective (but not more so) as psychological interventions (like therapy) or pharmacological interventions (like antidepressants). This is further evidence that we should not replace professional help with exercise, but it is good to know that all can be beneficial.

A 2017 study did just this: It separated people into two groups, one which received cognitive behavioral therapy (CBT) and one which received CBT and exercise. The investigators found that both interventions were effective, but the combined group showed better outcomes than the CBT-only group, including a decrease in suicidality.⁴

Can Exercise Prevent Depression?

A study out of Norway tracked 39,000 people over 11 years and assessed them for their exercise habits at the beginning, as well as their depression scores at the beginning and end. The authors concluded that if people exercised for just 1 hour a week, “12% of the cases at follow up could have been prevented.” Now at first glance 12% might not sound like a lot but so for context, if we apply that math to the United States, that is mental health protection for the entire state of California (our most populous territory).⁵

When looking at other studies, it seems like there are mixed but promising results. A recent review found that depressive symptoms could be reduced by physical activity, but there was not enough evidence to say that it truly prevents depression.³

Exercise & Anxiety

What about exercise’s effect on anxiety? What has been shown is that exercise is a helpful way to calm anxiety without the use of medication, but the effect is not as robust as it was for depression. Here is some evidence to that effect: Remember the meta-analysis that compared CBT alone with CBT plus exercise? Well it also looked at anxiety. When compared to each other, both appear to be effective, but one does not appear to be any more effective than the other, as it was with depression. However, the authors suggest that this may have more to do with how quickly exercise can act and when the anxiety scales were measured.

Several other studies have found more inspiring results. A 2015 study specifically looking at exercise as a treatment for anxiety determined that exercise has an effect that is equal to other types of treatments and more effective than placebo.⁶

Another compared 49 randomized controlled trials (RCT’s) and drew similar conclusions: exercise helped reduce anxiety, but the results were even more robust when combined with other anxiolytic (anxiety-reducing) treatments.⁷

Theories on Why Exercise Lowers Anxiety Levels

On a large scale, we have seen mixed evidence, but it is generally trending that anxiety can be helped by exercise. We don’t have exact answers but we do have some great theories. For example, one theory is that the same endorphins that help us ameliorate the effects of pain also assist in reducing anxiety, and are increased by exercise.¹¹ Within that same family, it is likely that endocannabinoids play a role in the anxiolytic effects of exercise as well.⁸

Serotonin, one of the neurotransmitters implicated in mood and affect, is likely increased and/or regulated by the act of exercising, which could help reduce both the feeling of anxiety and the physical response.⁹ Finally, brain-derived neurotrophic factor (or its more palatable acronym BDNF) might be involved here as well. BDNF is a neurotrophic family of its own, that helps build and maintain brain connections.

Guess what causes levels of BDNF to rise? That’s right—Exercise! BDNF is also very important in the process of learning. For certain types of anxiety, treatment is about learning to react differently to a perceived threat (i.e. exposure therapy), therefore there is an argument to be made that BDNF could be involved in that as well.^9,10

Another possibility is that it affects our psychology as well as our biology. People who complete an exercise activity have been reported to feel a “new level of mastery” from this task, which improves their mental state.⁹

There is also a possible explanation involving developing a lowered response through exposure, similar to what we just talked about above. It holds that when we exercise we are exposed to an unpleasant feeling. I love to exercise, but it can be uncomfortable! However, when we finish exercising, we show ourselves that we can tolerate the exposure to this anxiety-inducing state and increase our ability to believe that we can overcome it!¹¹

Exercise & Stress

Once again, we don’t have completely definitive answers but we have great theories and excellent evidence supporting them. We turn first to the Hypothalamic-Pituitary-Adrenal (HPA) axis. When we become stressed, this system is activated, releasing a cascade of hormones ending with glucocorticoids that prepare our bodies to react to whatever threat activates it. Normally the system acts in a cycle; activating for a stressor and then returning to homeostasis.

However, when the system is dysregulated it has trouble returning to normal, and that can lead to issues. When we don’t return to our baseline we get chronic stress. Exercise may have an effect on this by helping the body regulate this loop and keeping everything balanced.¹¹ Of particular relevance in this biological stress cocktail is cortisol. Cortisol is one of those aforementioned glucocorticoids, which helps signal the release of glucose to fuel our muscles, and other important reactions that help our body prepare to fight the stressor.

When this cycle is out of balance it can lead to negative effects on our brain health and physical health. Exercise has been shown to help regulate reactivity of cortisol to stress. In a 2014 study, researchers divided 96 people into three groups: An exercise group, a relaxation training group, and a control group. After 12 weeks, both the exercise and the relaxation group saw decreases in cortisol reactivity, but only the exercise group was statistically significant in their difference from the control.¹² We can infer from this that while it is likely that both exercise and relaxation have an effect on stress, we can be confident that something about exercising specifically was relevant for reducing stress.

What exactly happens when these things go out of balance? Well one theory is the “glucocorticoid cascade hypothesis.” This theory suggests that “chronic stress” leads to chronically elevated levels of those glucocorticoids, which causes problems. In our brains this means it means that our neurons are more frequently damaged and it affects our ability to create new neural pathways. Exercise can buffer the damage that the excess glucocorticoids have and also has been linked to helping increase neurogenesis.^13,14

Of notable mention here is our old friend BDNF. BDNF is a big player in the building of neuronal connections, thus why it was coined “Miracle-Gro for the brain” by Dr. John Ratey in his seminal book, Spark. Exercise has been well documented as a spreader of that fertilizer—your weekly jog is the equivalent for tobuying and sprinkling said fertilizer on your garden, but for your brain.

As said in a 2011 study on this subject: “Convergent evidence from animal and human studies indicates that BDNF plays an important role in modulating depression and hippocampal plasticity. Hippocampal BDNF level robustly increased in response to exercise and this increase remained high throughout the whole hippocampus with sustained exercise for weeks.”¹⁴ Or more simply put: Exercise increases BDNF and BDNF plays a role in alleviating depression and creating change in your brain.

How Much Exercise Do I Need to Reap the Benefits?

While more research is needed, there are some patterns that have been identified. One of the most frequent findings was for frequency. There is robust evidence that 3 times a week is a great minimum to hit for positive mental health effects. It also appears that those 3 sessions should be about 30-40 minutes in length, particularly if you are coping with a mood disorder.^13,15,16 Also, if the exerciser has the option to be supervised by a professional, this variable shows promise as well.

As for intensity, there are mixed results. Overall it appears that exercise at any intensity will create some benefit, and that there is no clear “dose-response” relationship; meaning that we don’t necessarily know that more is better.¹⁷ But a 2013 review in Neuropsychobiology noted some differences: “A meta-analysis conducted by Reed and Ones showed that low-intensity exercises that had a duration of 35 min or less also induced a strong activation of positive affect. In contrast, recent research has shown that an exercise protocol that included intervals of high-intensity generated more pleasure than a program that used a continuous moderate intensity. There is also evidence that suggests that positive behavioral outcomes tend to occur after exercising at a self-selected intensity.”¹⁸

Suffice to say, the jury is still out on specific numbers and dose-response but we can see that either one can be helpful!

It’s important to note that when exercise is done almost obsessively however, often as a response to a body image issue like muscle dysmorphia, it can become harmful.

5 Tips For Exercising When You’re Feeling Depressed or Anxious

It’s tough to start exercising. It’s even tougher when you are anxious or depressed. So first let’s take a moment to recognize that. I will admit to dealing with this myself! It can be particularly hard because the benefits are known to our mind for the long term, but in the short term it doesn’t seem as rewarding or enticing to our brains, especially when compared to other things that generate feel good chemicals more immediately (like snacks!).

These five tips can help you to exercise while feeling depressed or anxious:

1. Start Small & Grow

Begin with what is a manageable goal for you personally. A 10 minute walk? Sounds good! Start there and then add more. Go from 10 to 15, from 15 to 30, and so on and so forth.

2. Write It Out or Sign Up Ahead of Time

One of the tricks to easing the transition to a new behavior is to help yourself eliminate obstacles. First block out the time- tell yourself “6-645” tomorrow I am working out. Reserve it like you would a meeting. Go even further by outlining what you will be doing- if you are going to the gym, decide your routine ahead of time. Not sure about a routine? Sign up for a class!

3. Do It With a Friend, Partner, or in a Group

Doing an activity with someone else helps us in a couple of ways. One, it helps keep us accountable. Two, it can help make the activity itself more enjoyable. Not to mention neurologically we release oxytocin which is another feel good chemical that encourages us to continue to participate in this social interaction.

4. Set a Goal & Keep Track of It Visually

Let’s say you are aiming for physical activity 3 times a week. Print out and hang up a calendar and every time you are active mark it down. Much like finishing a 1000 piece puzzle, over time you will make a visual representation of your hard work. One that you will step back from, look at, and be proud of when you view the totality of your work.

5. Identify Yourself as a Person Who Exercises

This one is a little more psychological—apply the action to the quality of your person. In Acceptance and Commitment Therapy (ACT) there is a concept called “defusion” that I talk with my clients about. Basically it holds that sometimes we hold an idea so closely to ourselves that we “fuse” with it. When working clinically this can create difficulty.

For example, if you are fused to your identity as a punctual person but you show up late to a meeting, and beat yourself up inside for it, we might want to put into practice the concept of defusion- creating space from that identity and allowing some room for flexibility. You can still be a punctual person AND be occasionally late because life got in the way! We can use theopposite of this principle (fusion) to help us workout.

Instead of being just a person who did a workout you can begin to identify yourself as a person who exercises. This activity becomes not just something to do but an activity that aligns with who you are. Make it part of your identity rather than something you have to overcome about yourself.