Exercise: A Tool to help improve your Mental Health
Depression is one of the most common mental health disorders worldwide. According to the World Health Organization, over 264 million people suffer from depression and in the U.S., neuropsychiatric disorders are the leading cause of disability, followed by cardiovascular disease and circulatory diseases. In fact, depression is the leading cause of disability worldwide, making the need for effective treatments necessary and vital.
Current and most popular forms of treatment include psychiatric medication and psychotherapy, which depending on the severity of depression and the kind of modality of therapy, have mixed results. Psychiatric medications also have poor levels of compliance due to side effects and lack of efficacy overall, suggesting a real need for more effective treatments with less negative consequences. Over the past couple of decades, research has clearly demonstrated that physical exercise is an effective treatment for individuals suffering from depression.
Current evidence
The research on exercise is incredibly extensive and now, there are literally hundreds of studies demonstrating the benefits of exercise on mental health, including decreasing symptoms of depression and anxiety. Cross-sectional studies have demonstrated that people with higher levels of physical activity generally have decreased depressive symptoms, and these results are consistent across different countries and cultures. Due to the limitations within cross sectional studies, looking at the evidence from prospective cohort studies help give us a better picture regarding whether physical activity is truly a modifiable risk factor for depression. This meta-analysis included only prospective cohorts evaluating the effects of physical activity and incident depression in studies of at least 1 year follow up. Authors compared the incident depression in people with higher levels versus lower levels of physical activity at baseline, including a total of 49 studies, and a sample of 266,939 participants, accounting for a total of 1,837,794 person-years. Only studies with people free from depression at baseline were included in the analysis. They found that physical activity reduced the risk of depression by 17% in studies adjusting the odds for potential covariates and a reduced odds of 41% in studies that did not adjust their analysis for potential covariates and calculated using only raw numbers.
Here’s a quote from the results section: “According to our subgroups analyses, the protective effects were significant across all ages: children and adolescents (10% decreased odds), adults (12% decreased odds), and older adults (21% decreased odds); all the countries where we have found studies: Asia (24% decreased odds), Europe (17% decreased odds), North America (14% decreased odds), and Oceania (35% decreased odds); and the potential covariates included in the models for adjustment: age and sex (17% decreased odds), body mass index (13% decreased odds), smoking (26% decreased odds), and the combination of these three factors (17% decreased odds). The odds for those completing the 150 min of moderate to vigorous PA per week were decreased by about 22%.”
Now that we understand that there is indeed this relationship between physical activity and depression, let’s take a look at the most recent systematic review to see if there is some kind of dose response relationship when it comes to the overall effects of physical activity on depression in particular.
The purpose was to investigate the dose-response association between physical activity and depression. Previous to this review, other meta-analyses and studies typically used a binary categorization of low vs high activity in order to make a comparison between the effects of the frequency of activity and depression risk and symptoms, but this approach results in a loss of information and does not inform us about the variation in risk across a range of physical activity doses. This makes this particular review interesting and more informative.
The review included prospective cohort studies of adults (≥18 years of age) that reported any dimension of physical activity at 3 or more exposure levels and reported risk estimates for depression. With regards to outcome, depression was assessed via the following strategies: (1) presence of major depressive disorder indicated by self-report of physician diagnosis, registry data, or diagnostic interviews using DSM criteria or International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, codes F32 through F33; (2) elevated depressive symptoms established using validated cutoffs for a depressive screening instrument, (i.e.Center for Epidemiologic Studies Depression scale). With regards to the study breakdown,15 eligible publications were analyzed which included almost 200,000 participants contributing 28,806 incident depression events and over 2,000,000 person-years. Approximately 64% of participants in the studies were women and all but 1 of the included studies originated in high-income countries: 6 from the United States, 6 from Europe,1 from Australia, 1 from Japan, and 1 study that included data from India, Ghana, Mexico, and Russia.
With regards to findings, the authors report a "curvilinear dose-response association between physical activity and depression, with greater differences in risk in the lower-dose region.” And here’s what’s interesting. Compared to adults not reporting any activity, those accumulating half the recommended volume of physical activity (half of the 2.5 hour/week of physical activity of moderate intensity recommendation based on the WHO rec for adults) had 18% lower risk of depression while adults accumulating the recommended volume of 2.5 hours/week had 25% lower risk, with diminishing benefits and more uncertainty observed beyond that exposure level.
Here’s the biggest takeaway from this specific review. The greatest differences in depression risk was observed between low doses of physical activity, suggesting that most of the benefit results from going to no activity to at least some. Results indicate that accumulating a physical activity volume equal to 2.5 hours of brisk walking per week was associated with 25% lower risk of depression, and at half that dose, risk was 18% lower compared with no activity. And, there was only minor additional benefits when people engaged in activity at higher levels. I think this is really promising and encouraging in that going from no activity to something on a semi consistent basis, will actually result in substantial benefit in helping reduce your risk of depression.
And these findings have been replicated by many independent intervention studies evaluating the effects of physical activity on depression symptoms and risk. In general, estimating the dose-response relationship between physical activity and any mental health outcome using meta-analysis is challenging because of the differing methods of assessments and inconsistent reporting. When looking at the overall body of evidence for physical activity and depression risk, the findings are mostly consistent in that some form of regular physical activity is beneficial in helping to reduce symptoms and risk for depression in adults of varying ages.
Beyond just reducing symptoms of depression, exercise has now been shown to help potentially prevent it from manifesting in the first place. The study published early last year states that the ideal amount of exercise to prevent depression starts at about 15 minutes a day of running or other strenuous form of exercise. And how about this: Less-taxing activities like fast walking, housework and so on also afforded protection against depression, but it took about an hour a day of engagement in those activities to have an effect.
15 minutes a day, huh? That certainly is doable for anyone. The trick is that it needs to be “strenuous,” meaning, you need to get your heart pumping.
How does exercise create these results?
There have been many proposed mechanisms to help explain the positive benefits of exercise on our mental health and one of them includes increasing specific neurotrophic factors. Exercise increases certain neurotrophic factors, one of which is called BDNF. BDNF helps to promote neurogenesis in the hippocampus. This may be important for our mental health as low BDNF is associated with the presence of common psychiatric disorders like depression and neurodegenerative disease. BDNF is also essential for hippocampal functioning, learning and memory, and mood regulation. Another reason why we gain so many physical and mental benefits from exercise is because exercise increases blood flow, which means more oxygen and nutrients get transported everywhere in our body, including our brain. One study reports that an increase in blood flow to the brain, known as perfusion, occurred during a single 20 min session of moderate intensity exercise. And the perfusion targeted the hippocampus.
What exercise is best for your mental health
The short answer, is that one that you will do in a sustainable way. And according to most of the research, a physical activity routine that includes both aerobic and strength training is likely to be optimal for the prevention of depression. Fifteen minutes of moderately intense exercise is enough to give your brain healthy benefits by increasing levels of BDNF. If you want to reduce and prevent symptoms of depression, combining both aerobic and strength training a few times week is optimal. Aim for about 150 minutes a week, this could be broken into 30 minutes of exercise 5 times a week or 45 minute sessions 3 times a week. And if you really don’t have time to do that much during the week, 15 minutes a day of some kind of exercise that allows your heart rate to increase, can be beneficial in helping to reduce and prevent depression.
The amount of benefits that exercise gives our brain is innumerable. In addition to improving our mental health, exercise protects your brain from age related cognitive decline by reducing the number and size of age-related holes in the brain’s white and gray matter, it helps to potentially reduce your risk of neurodegenerative disease, has been shown in research studies to improve memory and attention in adults, promotes neurogenesis or the birth of new neurons in the hippocampus - our learning and memory brain structure, decreases inflammation, improves self esteem, and helps to improve the quality and amount of sleep.
Also, self-efficacy beliefs are important because the belief that one can exercise, given constraints and obstacles such as feeling tired or being busy, is associated with a greater likelihood of doing it. Did you catch that? Your belief that you can exercise despite feeling unmotivated, or tired, or too busy, actually makes you more likely to exercise and stick with an exercise routine. So please, do yourself and your brain a favor and strive for at least 20 minutes of exercise at least 3 times a week. Choose an activity that you enjoy and that you can do. Set your goal to be realistic, it’s common for people to go too fast too soon with setting exercise goals. Be mindful of where you are starting from and choose a small goal to focus on to help you gain efficacy, success, and momentum. And if you are in need of more support and guidance, check out my course, Building Mental Health.
A PSA
I want to be excruciatingly clear that not everyone’s mental health symptoms will respond as positively as these studies report just by hitting 150 minutes of exercise a week. Mental health is incredibly complex and not everyone’s mental health will respond in this exact way because everyone has a unique biological, social, and environmental context that inevitably creates our mental health. Exercise is a another potential tool to explore if you aren’t already in helping to support your mental health and well being.
References
https://www.who.int/news-room/fact-sheets/detail/depression
Craft, L., Perna, F. The Benefits of Exercise for the Clinically Depressed. J Exerc Rehabil. 2016 Oct; 12(5): 380–385.
Baek, S. Role of Exercise on the Brain. Prim Care Companion J Clin Psychiatry. 2006; 8(2): 106.
Bandura A. Self-efficacy: The exercise of control. New York: W. H. Freeman; 1997.
Choi, K., Chen, C., Stein, M., Klimentidis, Y., Wang, M., Koenen, K., Smoller, J. Assessment of Bidirectional Relationships Between Physical Activity and Depression Among Adults: A 2-Sample Mendelian Randomization Study. JAMA Psychiatry. 2019;76(4):399-408.
Kirsch I, Deacon BJ, Huedo-Medina TB, Scoboria A, Moore TJ, et al. (2008). Initial Severity and Antidepressant Benefits: A Meta-Analysis of Data Submitted to the Food and Drug Administration. PLOS Medicine 5(2): e45.
