Exercise as a Treatment Option for Depression: What Does the Science Say?

by Anne Guzman, sports nutritionist and former professional road cyclist.

Learn more about Anne’s work here >.

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If you’ve ever felt an uptick in mood after you exercise, you’re not imagining it.

Over the last decade, research surrounding the effects of exercise on mood disorders including depression and anxiety has become well known. Although evidence is growing quickly to support the use of exercise and physical activity as treatment options for depression, the translation of this to practice has been slow.

Depression and anxiety often co-exist and are frequently underpinned by chronic stress. In some people, a period of as little as six weeks of continuous stress can lead to a diagnosis of depression or anxiety.

Depression and anxiety during the COVID pandemic

Globally, the pandemic has exacerbated the prevalence of both depression and anxiety. A recent systematic review published in The Lancet investigated the effects of Covid-19 on the prevalence of major depressive disorder and anxiety and found the two factors which were most impactful were the daily Covid-19 infection rates and reductions in human mobility (or face-to-face time with other people).

Globally during the pandemic in 2020, an additional 28% of people experienced depression and an additional 26% experienced anxiety.

All safe, accessible, multidisciplinary therapy options need to be brought to the table to help ease the burden of the current mental health crisis. Science has shown that exercise can be a treatment option for people suffering from mild to moderate major depressive disorder.

Let’s look at why exercise needs more consideration as a treatment for depression, and the effect it’s having on our brains.

There is a range of effective treatments and health professionals who can help you on the road to recovery.

Here in Australia, most people who turn up to their G.P. and are diagnosed with anxiety or depression benefit from one or a combination of the following:

• lifestyle changes and social support 
• psychological or ‘talking’ therapies
• medical therapies

The website Beyond Blue offers excellent evidence-based information on symptoms, diagnosis, treatment and how to access support services.

As Beyond Blue states, there are also plenty of things you can do for yourself to recover and stay well. The important thing is finding the right treatment and the right health professional for your needs.

Let’s take a closer look at anti-depressant medication

In other parts of the world, anti-depressant medication is often the mainstay of treatment for depression. One of the most well-known medications is a group of drugs called selective serotonin reuptake inhibitors (SSRIs).

Other medications called norepinephrine and dopamine reuptake inhibitors (NDRIs), focus on dopamine and norepinephrine reuptake. Serotonin, dopamine, and norepinephrine are chemical messengers (neurotransmitters) that carry signals between brain nerve cells.

Let’s look at SSRIs as an example of how some antidepressants work.

When two nerve cells or neurons communicate with one another, one releases a chemical or neurotransmitter into the space between them. The gap is called a synapse. (Hold your two pointer fingers facing one another with a teeny space between them. Your fingers are the neurons, and the space would represent the synapse).

Serotonin released from the first neuron binds to specific serotonin receptors located on the second neuron. This causes a change in the electrical activity of the second neuron. Specific neuro-chemical recognition sites are called receptors. Neurotransmitters can only act on another neuron when their receptor is present. Think of a lock and key where the receptor is the lock and the neurotransmitter is the key. Turning the key sets off a cascade of biological responses inside the cell.

Typically, after interacting with its receptors, serotonin would be cleared from the synapse by a molecule that acts like a mini vacuum cleaner. Serotonin is taken back up into the first neuron for recycling and reuse.

However, when you take an SSRI, it slows that removal, essentially making more serotonin available in the synapse to interact with serotonin receptors. SSRIs don’t increase serotonin, instead serotonin sticks around in the synapse longer. Along with other changes to receptors, this increased uptake has been shown to help regulate mood.

Unfortunately, treatment is not always effective with SSRIs. One-third of people don’t seem to benefit or also suffered from side effects.

As the saying goes, “What works for some people some of time doesn’t work for all people all of the time,”

Exercise can be as effective as SSRIs in people with mild to moderate depression

Interestingly, studies have shown that aerobic exercise can be as effective as SSRIs in people with mild or moderate depression. Some people see clinically meaningful reductions in symptoms i.e. exercise makes a difference to their day-to-day mood. Exercise can also help promote the management of side effects.

This makes sense since both SSRIs and exercise appear to work through a similar biological pathway in the brain related to tryptophan, serotonin and its receptors [8],[9].

Therefore, when accessible, and where barriers to starting and sticking to exercise can be overcome, exercise should be considered as part of a multidisciplinary approach to the treatment of depression.

And here in Australia, lifestyle changes including exercise are recommended alongside psychological therapy and/or medication for people with mild to moderate depression.

What type of exercise is best to treat depression?

Both high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) have been proven beneficial for reducing the symptoms and severity of depression [10].

High-intensity interval training (HIIT):

You’ve may have seen or even participated in one of the many types of high-intensity interval training (HIIT).

HIIT includes alternating shorter bursts of high-intensity exercise with rest periods interspersed between bursts.

Typically, bursts are executed over 80% of V02 max (or maximum heart rate). You’re working hard! If you’re new to exercise, easing into this intensity can be important for motivation and injury prevention.

Examples of HIIT could include running a flight of stairs, cycling for 30 seconds hard, cycling for thee minutes at high intensity with three to five minutes rest (al of which would be followed by rest and then repeated). The work-to-rest ratios can change as fitness improves and are dependent on the type of program you are taking part in.

Moderate-intensity continuous training (MICT):

Less intense is moderate-intensity continuous exercise.

It’s completed at lower intensities and can range anywhere from 50% to 70% of maximum heart rate or power and for longer durations of 30-60 minutes, or longer if desired.

You should be able to have a conversation at the lower end of this pace. Examples would include a bike ride, jog, walking uphill on a treadmill or rowing.

Currently, most studies have investigated moderate-intensity continuous training in people with mild to moderate major depressive disorder as compared to high-intensity training or resistance training, although all three have been investigated and have shown benefits.

Exercise: as Effective as Anti-Depressants?

Several reviews have shown moderate to large clinical effects of exercise on different severities of depression, showing that exercise can be as effective as cognitive behavioural therapy, a type of psychotherapy recommended as a treatment option for depression.

Exercise interventions in these reviews ranged from six weeks to four months in duration. Two of the studies compared aerobic exercise to antidepressant medication and found both treatments were as effective at reducing major moderate depression [5],[6].

An important note is that people who continued to exercise 10 months after the study ended were 50%  less likely to be depressed versus those who stopped exercising [11],[5]. Sticking to your program can help you reap mental health benefits long term.

Public Health Recommendations for Exercise

Something Is Better Than Nothing

Although public health recommendations vary by country, several studies support these recommendations. The latest U.S. guidelines recommend at least 150-300 minutes per week of aerobic activity and the Centers for Disease Control and Prevention recommend the same or 75 minutes of vigorous-intensity exercise or a combination of both. This can be broken down into 30 minutes of exercise per day.

Here in Australia, adults up to 65 are recommended to be active on most (preferably all) days. We should aim for a weekly total of two and half to four hours of moderate activity or one to two hours of vigorous activity or an equivalent combination of both.  People older than 65 should aim for at least 30 minutes of moderate activity on most (preferably all) days.

If your schedule is tight, you can break this time down into three 10-minute exercise bouts per day, which may be great to break up long periods of sitting! Exercising for less time has also been shown to improve symptoms of depression, and what’s most important is that you start, even if it’s 5 minutes a day. You can build up to longer durations.

Social support from group settings can be an important contributor to success and may potentially add a much-needed element of comradery and accountability to an exercise program.

In addition, by increasing adherence we can improve other health outcomes including cardiovascular health and bone health, which also contribute to our overall quality of life, reduced disability and healthspan.

45 minutes, 3-5 times a week: is this the exercise sweet spot?

In 2018, the biggest study to date was published in Lancet Psychiatry looking at the role of exercise and mental health.

Amongst over 1.2 million people in the USA between 2011-2015, people who exercised had about 40% better mental health than people who didn’t exercise, even after the researchers controlled for BMI, physical health, and sociodemographic.

In a Twitter thread about the paper, author Adam Chekroud noted:

People who exercised for about 45 minutes seemed to have better mental health than people who exercised for less than 30 or more than 60 minutes — a sweet spot for mental health, perhaps?

People who exercised 3-5 times a week seemed to be feeling better than people who were outside that zone.

Adam Chekroud

The type of exercise people did seemed important too.

People doing team sports or cycling had much better mental health than other sports. But even just walking or doing household chores was better than nothing!

Here are four ways exercise affects our mood.

Exercise affects our mood through many different pathways in the brain and body, related to pain, inflammation, and gene expression.

1.Endocannabinoids

When we exercise, our bodies increase the circulating concentration of molecules called endocannabinoids, which give rise to an uplifted mood, and feelings of reduced stress and anxiety, leaving us feeling calm and at ease. Endocannabinoids are molecules we produce naturally in the body that have a similar effect to cannabis (yes marijuana!). Unlike endorphins, endocannabinoids can pass through the blood-brain barrier into the brain.

Emerging evidence suggests our mood can be lifted immediately, and as long as 30 minutes post-exercise from increases in circulating endocannabinoids. Although the exact mechanisms are not well understood, there is evidence to suggest endocannabinoids affect the movement of neurotransmitters from one nerve cell to another and they may play a role in regulating the inflammatory process, both which are important in the management of depression and anxiety.

2. Stress and Inflammation

Stress is important, for example, stress from exercise and learning leads to positive muscular and cognitive adaptations. Longer periods of high stress, however, are correlated with increased bouts of depression and anxiety. These long-term stressful episodes impact our immune system, which can lead to increased inflammation.

People with major depressive disorder have been found to have increased markers of inflammation in their blood. This immune response leads to an increase in what are called inflammatory cytokines. These cytokines impact the production, uptake, and release of the important neurotransmitters serotonin, dopamine and norepinephrine that help regulate our mood.

Inflammatory cytokines also activate another pathway called the kynurenine pathway, which ultimately results in less serotonin production. Together, the repercussions of these changes from increased inflammation can affect our mood regulation.

Exercise can reduce inflammation and contribute to the optimal production, uptake, and release of these important mood-regulating neurotransmitters leading to a significant reduction in the symptoms of depression.

Moderate-intensity continuous exercise may be the best type of exercise to reduce inflammation as compared to HIIT. Since the brain and body communicate, the anti-inflammatory effects of exercise can act systemically throughout the body and centrally on the brain, strengthening our brains against any chronic inflammatory response from long term stress.

3. Synaptic Plasticity and Increased Blood Vessels

Exercise has been shown to increase synaptic plasticity through its effects on synaptic structure and potentiation of synaptic strength. Above I mentioned that a synapse was the space between two nerve cells, where SSRIs increase serotonin availability. Imagine now that one nerve cell is referred to as presynaptic while the one facing it is the postsynaptic, and the space between is where a neurotransmitter, such as serotonin, would transfer a nerve impulse to the postsynaptic fibre and bind to its membrane.

Exercise positively impacts these structures and the synaptic strength of the presynaptic nerve cells, making it more likely that neurotransmitters will elicit their response from receptors [20]. This has been shown to occur in the hippocampus, an area of the brain which has been associated with mood regulation as well as memory and learning.

In addition, exercise has also been shown to produce new brain cells and retain brain volume in the hippocampus and can lead to the generation of new blood vessels, an important means of nourishing the brain.

4. How Your Muscles Relate to Improved Mood

It turns out that your muscles themselves may contribute to mood-enhancing effects of exercise. When we exercise, a series of events occur that lead to increased metabolism of tryptophan, which is required to form serotonin, which we as we have discussed plays an important role in mood regulation. You’ve probably heard about the post-turkey dinner tryptophan spike!

In the body, if tryptophan metabolism is impaired, this can lead to low levels of serotonin, often associated with major depressive disorder.

When tryptophan is metabolized it is broken down into kynurenine, which can pass into the brain and undergo further metabolism into one of two pathways. From here kynurenine can either become toxic to the brain or protective of the brain referred to as neurotoxic or neuroprotective.

How does exercise fit into this picture? When you do both aerobic and strength training exercises, there are factors within the muscle itself that promote tryptophan metabolism towards the neuroprotective pathway.

Although more research needs to be done in this area, preliminary research is promising that these changes in tryptophan metabolism could lead to neuroprotection and help with symptoms of depression and anxiety. Keep lifting!

14 Ways to Overcome Barriers to Exercising

It’s tough enough to start an exercise regime, and we know it’s even tougher when you’re struggling with depression.

Here are some tips to get started, overcome barriers, optimize your environment, and keep you accountable for sticking to it.

1. Set a GOAL. Start small. Five minutes beats zero minutes. Extend your time/intensity slowly.
2. Start with an exercise you’re familiar with if you have a history with something.
3. Exercise in the first 8 hours of the day, if possible, when you’re more alert mentally.
4. Do something you ENJOY!
5. For short term motivation when you start, reward yourself for completing an exercise session.
6. Consider HIIT training for time constraints and the likelihood of sticking to a program. If you struggle with anxiety, give yourself a rest day or two between HIIT workouts as it has been shown to increase anxiety in some people.
7. Dial-in your nutrition so you have the energy for both exercise and life.
8. Have stable cues for your new habit. For example, exercise every day ‘after breakfast,’ or exercise when you get to the ‘gym.’ Cues can be location, time, or another specific context.
9. In advance, imagine how you will feel before, during and after you finish exercise.
10. Listen to music you love and consider joining a group that exercises to music if you love music.
11. Plan your exercise for the week and what time you will do it at. Adjust if necessary but plan it!
12. Join an exercise group or friend for accountability.
13. Join a challenge or give yourself a weekly goal. Make it achievable, and build momentum.
14. Record how you feel after sessions and record your triumphs! Note mood changes and check back on your journal the next time you don’t want to exercise. Positive reinforcement is good!

Many people who struggle with depression have co-existing medical conditions including diabetes and heart disease. We know that exercise can prevent, manage, and reverse type two diabetes and improve heart health. By including exercise in your life, you have the potential to improve your mental health, including symptoms of depression, as well as many other aspects of your health, improving your lifespan and healthspan.

Reach out to a friend, join a local club, and trust that by moving your body, creating social connections, and getting outside you will benefit your body and free your mind.

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By Anne Guzman, sports nutritionist and former professional road cyclist.

Learn more about Anne’s work here >.

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