The COVID-19 pandemic has caused many of us to be less physically active over the past two years, and that can affect our mental health.
When we exercise, dance, play with our kids, ride a bike, shoot hoops, walk to work or any other activity that makes our hearts beat faster, our lungs take in more oxygen and our muscles get stronger. For these reasons, an active lifestyle is good for our physical health.
An active lifestyle is also incredibly good for our mental health. This is especially true during a pandemic when we may have developed or increased health disorders, such as depression and anxiety. Why does exercise, especially aerobic activity that increases our heart rate, immediately reduce levels of depression, anxiety and stress? Why does it improve memory and slow the effects of mental decline as we age?
Although we know the positive health outcomes from physical activity, we are still learning about the underlying biological processes that lead to them.
Our brain contains an estimated 100 billion brain cells, known as neurons, that send messages to each other, along 100 trillion lines of communication. The strength and efficiency of these connections are fundamental to memory, learning, our thinking and our mood.
Exercise is associated with the same brain activity observed after someone receives medication or therapy for depression. Both situations activate numerous chemicals that protect and promote healthy cells.
“You are activating chemical messengers (neurotransmitters), increasing cell formation and survival, and impacting neural connections,” said Dr. Margaret Cary, MD, MPH, a psychiatrist and senior health advisor for Oregon Health Authority.
Proteins and neurotransmitters released during exercise:
BDNF (Brain-derived neurotrophic factor) is a protein that protects and promotes the growth of neurons, helping them communicate with each other. It also helps build and maintain the circuitry of our brains.
VEGF (vascular endothelia growth factor) is a protein that promotes healthy blood vessels.
“Evidence suggests that aerobic exercise can increase molecules in the brain, such as BDNF. In turn, BDNF is known to increase VEGF which supports blood vessels,” said Dr. Lindsey Wooliscroft, assistant professor of neurology at Oregon Health & Science University. BDNF may play an important role in depression and decreased levels of BDNF are seen in cognitive disorders including Alzheimer’s and Parkinson’s, as well as mental illnesses such as depression.
Dopamine is a neurotransmitter our brains produce when we do something pleasurable, making it a part of our “reward system” that motivates us to do activities. It’s plays a role in memory, attention, mood, learning, behavior and cognition. Low levels of dopamine are associated with many diseases including attention deficit hyperactivity disorder (ADHD), and perhaps most notably in Parkinson’s disease where “weakened neurons produce lower levels of dopamine.” This causes the slowed movement disorder indicative of Parkinson’s.
High levels of dopamine, on the other hand, are associated with addiction, mania and obesity.
When there is too much dopamine activity in some regions of the brain and too little in others, that’s called “dopamine dysregulation.” Schizophrenia is an example of this.
Norepinephrine is a neurotransmitter and hormone connected to our “fight-or-flight” response that helps maintain blood pressure and alertness when you’re under stress. It is also affects your mood, memory, sleep cycle and attention. Low levels of norepinephrine are associated with anxiety, depression, ADHD, memory and sleep problems.
High levels of norepinephrine are associated with high blood pressure and a higher risk of heart, blood vessel and kidney damage.
Serotonin is a neurotransmitter and hormone. As a neurotransmitter it regulates your mood, contributes to sleep quality and promotes digestion. Our “gut feelings” may be driven by serotonin activity in our gastrointestinal tract and brain. It is also related to impulse control and self-esteem. Low levels of serotonin are strongly associated with depression and anxiety.
It’s difficult to study how molecules interact in the brain and “unravel the mechanisms behind exercise,” Wooliscroft said. “However, studies suggest that higher levels of exercise and aerobic fitness can lead to increased volume (or size) of the hippocampus (a brain structure which has a role in learning and memory) and may increase the thickness of the cerebral cortex (which is involved in a number of brain functions).”
We do not yet understand how all the parts of our nervous system work together, but we know everything is connected. For example, norepinephrine as a neurotransmitter is made from dopamine. Serotonin and dopamine work together to impact the length and quality of your sleep. And these neurotransmitters regulate each other through a feedback loop.
Researchers evaluated 23 studies that examined the efficacy of exercise treating depression and found exercise to be an “effective treatment for unipolar depression” and “comparable to psychotherapy and antidepressants for depression.”
For people with mild to moderate depression, exercise may be the first “medicine” people want to try.
“When you exercise, you are an active participant in your treatment. That has a profound impact on your mental health,” Cary said. “So the benefits of exercise are two-fold. One, exercise improves the health of our body, and second, by exercising we are improving our mental health. This gives us pride and increases our self-determination and can counter some of our self-critical thoughts.”
As we age, neural connections break down, causing our memories to begin to fade. Remembering the people, places, and events important to us becomes more difficult. Evidence suggests that strengthening those connections in our brain may help prevent cognitive decline later in life.
“It could be that there are certain time periods, especially earlier in life, when it is good to ‘invest’ in your physical fitness so you can see the ‘returns’ later in life,” Wooliscroft said.
Scientists followed 200 Swedish women ages 38 to 60 for an average of 29 years. Result published a few years ago showed that participants with high levels of physical fitness were 88% less likely to develop dementia than those with medium physical fitness levels.
Another study of adults over 45 in the United States found that “cognitive decline is almost twice as common among adults who are inactive compared to those who are active.”
Dr. Woolisroft says many of her patients during the pandemic have suffered from anxiety and isolation as gyms closed and yoga classes were canceled. Getting back into that routine or starting one for the first time can be a challenge, even if it’s to add a short walk to your daily to-do list.
“For most people, it is helpful to build in some accountability to help them stick with their exercise goals,” said Wooliscroft.
Dr. Cary agrees. “When we feel depressed, anxious, have a manic episode or are overwhelmed by trauma symptoms, we often disconnect from our healthy routines. Exercise can help us reconnect to those healthy routines, such as regular sleep and social contact. It can help us be outside or with a supportive community, both of which also sustain and strengthen our mental health.
“Exercise can pull us through that period of significant stress when we are feeling down,” Cary said.
One size does not fit all
We each have different abilities and preferences for being active. Many of us have difficulty finding the time. Some of us may never truly enjoy exercise but are motivated by its benefits. An exercise activity that is enjoyable, sustainable and suited to our abilities and fitness goals is the ideal combination to maximize physical and mental health benefits.
Additionally, not every type of exercise is going to benefit everyone in the same way. For some of us, an exercise routine is important; for others, changing our activities keeps us engaged. Finding what works best often requires some experimentation. Consider taking time to observe how exercising influences your mental health. For example, does it help you to sleep more soundly? Does exercise help you find peace with, or problem solve, stressful situations? Does it lift your mood? Does it spark motivation and energy? Does it help you settle and calm?
Answering these questions may help you figure out what’s best for you.
“It’s important to be kind to yourself and not get too worked up about hitting an unrealistic fitness goal too quickly—some exercise is better than none!” Wooliscroft said. “You may never be someone who looks forward to exercise, but always keep in mind that it’s an investment in your healthy future.”
If you have questions about whether it’s healthy for you to exercise, or if you have significant health conditions that impact your health, talk to your health care provider before starting an exercise routine.