Ben Dorfman

Position Paper

April 28th, 2019

The Benefits of Exercise on the Adolescent Mind

Adolescents make up about 13% of the United States population and worldwide there are about 1.2 billion adolescents (Sivagurunathan, 2015). Adolescence is a tumultuous time as it bridges the naive innocence of childhood with the responsibility and obligations of adulthood. The first symptoms and onset of many psychiatric disorders appear during this time period (Kessler, 2007). The prevalence of psychiatric disorders amongst adolescents has been increasing for the last 20-30 years. Recent estimates suggest that approximately 12% of adolescents struggle with a psychiatric disorder.  

The neurophysiological changes that occur during this time period (activation of neural pathways such as the HPA and HPG axis) contributes to increased stress. Compounded with the stress of physiological changes, adolescents face many environmental stressors such as the desire to fit in with peers and pressure to succeed academically and extracurricularly. With all the chaos that occurs during this time period researchers are finding new ways to help reduce the stress of this cohort so that most of us can grow into healthy adults who contribute to society.

One of the methods that is being researched is the effect of exercise on mental well-being. It is my belief that physical exercise (especially prolonged aerobic exercise) can be an effective treatment for several psychiatric disorders experienced during adolescence especially bipolar disorder and depression.

Physical exercise modulates genes that promote structural changes in the brain to enhance cognitive function and overall well-being (Mandolesi, 2018). Even acute exercise is proven to have positive effects on individuals. In one study conducted by A.W. Metcalfe and his team, bipolar adolescent subjects were subjected to a 27 minute interval session of aerobic exercise. The neurophysiology of diseases like bipolar disorder are still being understood but several researchers have begun to conclude that it may be due to a dysfunction of the ventral-striatal dopaminergic pathway (Cousins, 2009). After the patients were done with the exercise the researchers found normal levels of activation of the reward pathway compared with healthy control subjects. In conjunction with normal baseline activity of these neurological circuits came a reduction in the symptoms found in bipolar patients. It has long been known that the effects of exercise have improved the symptoms of bipolar patients.

The mechanisms responsible for these neurologic changes following exercise are the subject of much research. Some studies have shown that the increase of brain-derived neurotrophic factor (BDNF) in the striatum are responsible for the positive symptoms following exercise (Schuch, 2015) (Marais, 2009). BDNF is a gene that is involved in neural development, but has several other functions. BDNF enhances neural transmission and aids in learning and memory by promoting neurogenesis in the hippocampus (Liu, 2017). It is well established that exercise contributes to increased dopamine levels. Exercise is also closely associated with endorphins which are endogenous opiates that function as pain-reducers. The changes in endorphin levels that are seen post-exercise may contribute to the activation of the meso-limbic dopaminergic pathway (Spanegel, 1992).

Other biological effects of exercise are ATP/ADP ratio shifts, fluctuations of intracellular Calcium (Ca2+), and activation of other oxidation pathways (Vina, 2012). The psychoactive mechanisms of exercise are due to a variety of factors. The increased release B-Endorphin during physical exercise may lead to the euphoria experience. (Bortz, 1981). The response of several stress hormones such as ACTH and cortisol fluctuates during exercise (Harper, 1984). These stress hormones may lead to altered pain perception, but researchers are unsure what the differences in these hormone levels mean. In addition to the BDNF gene discussed earlier, exercise leads to an increase in glial cell derived neurotrophic (GDNF) factor and insulin growth factor (IGF). GDNF is another important chemical that helps promotes survival and IGF is involved in the proliferation and function in nearly every cell.

The World Health Organization recommends 60 minutes of moderate-vigorous physical activity a day for 11-17 year olds. According to the World Health Organization, 81 percent of 11-17 year olds did not meet this recommendation. In the United States, 3 out of 10 high school students participated in regular physical activity (CDC, 2017). The decline in physical activity usually occured between the ages 9-15 (Cairney). The decrease of physical exertion during these formative years has been linked to decreases in perceived parental support, self-efficacy, socialization and attention (Dishman, 2017). Routine physical exercise as an adolescent is more likely to lead to an increase in exercise as an adult (Sacker, 2006). Routine physical activity (aerobic exercise) reduces the risk for cardiovascular disease, type 2 diabetes, and even specific types of cancer (Ashcraft, 2016). Animal studies have shown that running increases neuronal cell proliferation, differentiation, and survival (Cotman, 2002).

Why does exercise have such a profound effect in adolescents. As mentioned earlier, adolescence is a formative period of development in which the brain is undergoing immense changes and thus is more sensitive to changes in the environment. The activation of the reward pathways during adolescents may serve as a reinforcer to the positive emotions felt following exercise.

There are four different psychosocial explanations for the effects of physical activity on mood. The first one posits that physical activity is a distraction and that is what contributes to the positive effects rather than any biochemical process. The second explanation states that the sense of achievement from exercise contributes to the increased mood. The third explanation hypothesizes that an increase in social opportunity is brought on by many forms of exercise leading to an increased mood. Lastly, the fourth theory states that exercise helps ‘body form’ which leads to an increase in self-esteem. While I think there may be truth in all of these explanations, I believe that the correlation between exercise and mood is not purely psychosocial and that there is also a neurobiological explanation. Many psychosocial factors do play a role in the prevalence of physical activity. For example, an individual in a lower SES may have to work many more hours than somebody in a high SES which would not allow that individual in the lower SES to have time to participate in regular physical activity. In addition, adolescents in lower SES often live in areas where crime is prevalent and access to recreational areas, such as parks and gyms is not feasible.

Depression is one of the most prevalent psychological disorders amongst adolescence. Prolonged exercise has been proven to mitigate the effects of depressive symptoms. In one study, participants aged 11-14 were recruited and then followed for two years. During this time and after two years the subjects filled out the Short Moods and Feelings Questionnaire. These researchers found an 8% decrease in depressive symptoms for each additional hour exercise undertook per week (Rothon, 2010). In another study adolescents and young adults (aged 12-25) who had depression were recruited. These individuals underwent periods of prolonged aerobic exercise several times a week for an eight week period. A reduction in overall depressive symptoms was found after the eight week period. In a study done by the Institute of Mental Health and the University of Ottawa, depressed adolescents who had not been using pharmacological treatment tried prolonged aerobic exercise to treat their symptoms. Three times a week for twelve weeks subjects participated in aerobic exercise for 45 minutes each time. Anxiety was measured after each session with Generalized Anxiety Disorder 7 Item Questionnaire. A decrease in depressive symptoms and anxiety was seen amongst subjects. This study was a landmark study as it is one of the firsts to treat depression with aerobic exercise (Jaworska, 2019).

Before the invention of agriculture humans had to constantly move locations in order to find the resources to survive. This active lifestyle of movement has been lost in modern times as we no longer need to constantly move in order to survive. The loss of an active lifestyle is a major consequence of the modern world that I believe has led to a decrease in overall life satisfaction for many individuals. How can we as a society promote an active lifestyle? The U.S. government lists physical exercise at the top of the public health agenda. But for many people, school, and jobs prevent them from finding time. I believe that increased education of the positive factors of exercise as well as increased time in schools that allow adolescents to play outside and move around could increase mental well-being significantly.

In my life, physical exercise has had a tremendous effect on my well being. As a high school freshman I attended a public school with over 1,000 kids in my class. Transferring from a small private school in another town I did not know a single kid. This experience brought about extreme anxiety and confusion. A couple months into my freshman year I was diagnosed with depression. My parents and I decided not to try pharmacological treatment over the fear of long term side effects. After a brutal freshman year, the fall of my sophomore year came about and I was still just as shy and scared as I was a year prior. To my dismay, my mother forced me to join the cross country team. Reluctantly and angrily I started going to cross country practice. Little did I know this was a defining moment in my life. I found the running to be difficult, but I enjoyed the challenge and it allowed me to finally connect with some of my peers. Flash forward four years later to today and I still continue to run religiously.  After a run I am more energized, productive, and sociable. I believe this to be a consequence of several of the factors that I discussed earlier.

In our society, the amount of psychiatric disorders is increasing along with the amount of psychiatric drugs. In my life, I would say that over half my peers take some sort of psychiatric drug daily. I find it very strange that so many people regularly take antidepressants, mood stabilizers, or stimulants. For many people, these medications are ineffective or have adverse side effects. I believe it would be beneficial to experiment with other types of therapy such as physical exercise to aid in these mental illnesses.

Works Cited

Sivagurunathan, C., Umadevi, R., Rama, R., & Gopalakrishnan, S. (2015). Adolescent health: present status and its related programmes in India. Are we in the right direction?. Journal of clinical and diagnostic research : JCDR, 9(3), LE01–LE6. doi:10.7860/JCDR/2015/11199.5649

Kessler, R. C., Amminger, G. P., Aguilar-Gaxiola, S., Alonso, J., Lee, S., & Ustün, T. B. (2007). Age of onset of mental disorders: a review of recent literature. Current opinion in psychiatry, 20(4), 359–364. doi:10.1097/YCO.0b013e32816ebc8c

Mandolesi, L., Polverino, A., Montuori, S., Foti, F., Ferraioli, G., Sorrentino, P., & Sorrentino, G. (2018). Effects of Physical Exercise on Cognitive Functioning and Wellbeing: Biological and Psychological Benefits. Frontiers in psychology, 9, 509. doi:10.3389/fpsyg.2018.00509

Metcalfe, A. W., MacIntosh, B. J., Scavone, A., Ou, X., Korczak, D., & Goldstein, B. I. (2016). Effects of acute aerobic exercise on neural correlates of attention and inhibition in adolescents with bipolar disorder. Translational psychiatry, 6(5), e814. doi:10.1038/tp.2016.85

Schuch, F. B., da Silveira, L. E., de Zeni, T. C., da Silva, D. P., Wollenhaupt-Aguiar, B., Ferrari, P., ... & Kapczinski, F. (2015). Effects of a single bout of maximal aerobic exercise on BDNF in bipolar disorder: a gender-based response. Psychiatry research, 229(1-2), 57-62.

Marais, L., Stein, D. J., & Daniels, W. M. (2009). Exercise increases BDNF levels in the striatum and decreases depressive-like behavior in chronically stressed rats. Metabolic brain disease, 24(4), 587-597.

Cousins, D. A., Butts, K., & Young, A. H. (2009). The role of dopamine in bipolar disorder. Bipolar disorders, 11(8), 787.

Thomson, D., Turner, A., Lauder, S., Gigler, M. E., Berk, L., Singh, A. B., ... & Sylvia, L. (2015). A brief review of exercise, bipolar disorder, and mechanistic pathways. Frontiers in psychology, 6, 147.

Spanagel, R., Herz, A., & Shippenberg, T. S. (1992). Opposing tonically active endogenous opioid systems modulate the mesolimbic dopaminergic pathway. Proceedings of the National Academy of Sciences, 89(6), 2046-2050. Herting, M. M., & Chu, X. (2017). Exercise, cognition, and the adolescent brain. Birth defects research, 109(20), 1672-1679.

Cairney, J., Veldhuizen, S., Kwan, M., Hay, J., & Faught, B. E. (2014). Biological age and sex-related declines in physical activity during adolescence. Medicine & Science in Sports & Exercise, 46(4), 730-735.

Dishman, R. K., Dowda, M., McIver, K. L., Saunders, R. P., & Pate, R. R. (2017). Naturally-occurring changes in social-cognitive factors modify change in physical activity during early adolescence. PloS one, 12(2), e0172040.

Sacker, A., & Cable, N. (2006). Do adolescent leisure‐time physical activities foster health and well‐being in adulthood? Evidence from two British birth cohorts. European Journal of Public Health, 16(3), 332–336.

Ashcraft, K. A., Peace, R. M., Betof, A. S.,Dewhirst, M. W., & Jones, L. W. (2016). Efficacy and mechanisms of aerobic exercise on cancer initiation, progression, and metastasis: A critical systematic review of in vivo preclinical data. Cancer Research, 76(14), 4032–4050.

Cotman, C. W., & Engesser‐Cesar, C. (2002). Exercise enhances and protects brain function. Exercise and Sport Sciences Reviews, 30(2), 75–79.

Wiles, N. J., Haase, A. M., Lawlor, D. A., Ness, A., & Lewis, G. (2011). Physical activity and depression in adolescents: cross-sectional findings from the ALSPAC cohort. Social psychiatry and psychiatric epidemiology, 47(7), 1023–1033. doi:10.1007/s00127-011-0422-4

Rothon, C., Edwards, P., Bhui, K., Viner, R. M., Taylor, S., & Stansfeld, S. A. (2010). Physical activity and depressive symptoms in adolescents: a prospective study. BMC medicine, 8, 32. doi:10.1186/1741-7015-8-32

Bailey, A. P., Hetrick, S. E., Rosenbaum, S., Purcell, R., & Parker, A. G. (2018). Treating depression with physical activity in adolescents and young adults: a systematic review and meta-analysis of randomised controlled trials. Psychological medicine, 48(7), 1068-1083.

Liu, P. Z., & Nusslock, R. (2018). Exercise-mediated neurogenesis in the hippocampus via BDNF. Frontiers in neuroscience, 12, 52.

Jaworska, N., Courtright, A. K., De Somma, E., MacQueen, G. M., & MacMaster, F. P. (2019). Aerobic exercise in depressed youth: A feasibility and clinical outcomes pilot. Early intervention in psychiatry, 13(1), 128-132.

Vina, J., Sanchis-Gomar, F., Martinez-Bello, V., & Gomez-Cabrera, M. C. (2012). Exercise acts as a drug; the pharmacological benefits of exercise. British journal of pharmacology, 167(1), 1–12. doi:10.1111/j.1476-5381.2012.01970.x

Bortz 2nd, W. M. (1981). Catecholamines, dopamine, and endorphin levels during extreme exercise. N Engl J Med, 305, 466-467.

Harber, V. J., & Sutton, J. R. (1984). Endorphins and exercise. Sports Medicine, 1(2), 154-171.

McCloskey, D. P., Adamo, D. S., & Anderson, B. J. (2001). Exercise increases metabolic capacity in the motor cortex and striatum, but not in the hippocampus. Brain research, 891(1-2), 168-175.