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Exercise is Good for Mental Health
Len Kravitz, PhD

Study Reviewed:
Chekroud, S.R., Gueorguieva, R., Paulus, M. et al. (2018). Association between physical exercise and mental health in 1.2 million individuals in the USA between 2011 and 2015: A cross-sectional study, Lancet Psychiatry, Published online

The benefits of exercise for reducing the risks of mortality, cardiovascular disease, stroke and cancer are very well understood and reported (Booth et al., 2012). In the area of mental health benefits of exercise, Booth et al. summarize research observing that active people are nearly 45% less likely to have depressive symptoms than inactive people. However, several specific questions remain in regards to exercise and mental health such as: 1) How do factors such as frequency, duration, and intensity of exercise relate to mental health? 2) Are all types of exercise equally effective and beneficial for mental health? A recent publication by Chekroud et al. (2018) presents new findings on these pertinent questions.

Methods: The Survey and Mental Health Component
Chekroud and colleagues (2018) examined data of 1,237,194 people (&Mac179;18 years from throughout the US) from the Behavioral Risk Factor Surveillance System Survey conducted by the Centers for Disease Control and Prevention during the years 2011, 2013 and 2015. In the survey, one of the questions used to help identify a person with a diagnosis of depression or depressive episode was: “Has a doctor, nurse, or other health professional EVER told you that you have a depressive disorder, including depression, major depression, dysthymia, or minor depression?" The researchers measured mental health impact according to each participants' self-report with the question: “Now thinking about your mental health, which includes stress, depression, and problems with emotions, for how many days during the past 30 days was your mental health not good?”

Methods: The Physical Activity Data Acquisition
To interpret the level of physical activity and the type of exercise, the survey had this question. “During the past month, other than your regular job, did you participate in any physical activities or exercises such as running, calisthenics, golf, gardening, or walking for exercise?” A participant yes response prompted this follow-up question. “What type of physical activity or exercise did you spend the most time doing during the past month?” The researchers grouped 75 different types of exercise into categories (i.e, walking, popular sports, cycling, aerobic or gym, running or jogging, recreational, winter or water sports) to help the participants identify their specific physical activities. The survey participants reported the number of times per week or month that they did this exercise as well as the number of minutes (or hours) they typically spend exercising at a session.

Study Results
Using a variety of complex statistical measures, the researchers were able to answer several previously unclear questions on exercise and mental health. To target specific results of the study, the following question/answer format is being utilized with this research column.
1. How effective is exercise in managing the burden of self-reported mental health problems.
Study Answer (SA): In the analysis of 852,068 participants (of the 1.2 million participants in the study) the researchers found that exercise was associated with 43.2% lower self-reported mental health burdens per month (as compared to those who did not exercise). This correlation between exercise and mental health burden was observed throughout for men and women (of all ages), as well as across all racial groups and all levels of household income.

2. Did all types of exercise appear to positively influence mental health?
SA: Yes, all types of exercise were associated with a reduction in mental health burdens. The strongest correlations were found for popular sports (22.3% lower), cycling (21.6% lower), and aerobic and gym exercises (20.1% lower) as compared to non-exercising participants. With regards to mindful exercises, yoga and tai chi showed a 22.9% reduction in mental health burden as compared to the non-exercising participants.

3. Is there an optimal duration per exercise session that appears to most positively influence mental health burdens?
SA: Yes, exercise durations between 30 min and 60 min were correlated with the lowest mental health burdens. The best effect was with exercise duration of 45 min. This optimal duration was consistent across all exercise types. Individuals who exercise longer than 90 min in an exercise session have a slight decrease in mental health burdens (meaning the 90-min session is not as effective). Persons exercising more than 3 hours per session were associated with worse mental health burdens as compared to those exercising for either 45 min or to those not exercising at all. So, very prolonged exercise sessions (>3hrs) are less effective in helping to manage any mental health burdens.

4. Did the study determine an optimal number of days/week of exercise that appears to lower mental health burdens?
SA: Yes, persons who exercise between three and five times a week had lower mental health burdens than those who exercised less than three or more than five times. This pattern was consistent across all exercise types and true for light, moderate and vigorous exercise intensity.

5. Is there an intensity of exercise that shows a more favorable decrease in mental health burdens?
SA: Yes, vigorous exercise is associated with more favorable mental health burdens outcome as compared to either light or moderate exercise.

Take Home Messages and Reflections
This study is the largest cross-sectional study to date investigating the effect of exercise on mental health. People, of all ages and socioeconomic backgrounds, who exercise report fewer mental health problems as compared to non-exercises. Exercise sessions lasting between 30-60 minutes provide the best outcome in minimizing mental health burdens with 45 minutes being a peak duration. Engaging in exercise at least 3-5 times a week on a variety of exercise modes is an appropriate frequency and exercise mode choice to realize mental health benefits. Also, when it comes to mental health and exercise, more exercise is not better. Those persons exercising more than 23 times per month, or longer than 90 min per session, were associated with worse mental health outcomes.
Interestingly, this study found that popular sports, mostly team sports, were correlated with the lowest mental health burden. The researchers state that this finding is in line with previous studies showing that social activity reduces depression and promotes a hardiness to stress. The finding that mental health stress is reduced with team sports may suggest there are favorable stress effects for people involved in group exercise. Group exercise is also a social activity. More research on this specific hypothesis is warranted.

This immensely large study by Chekroud and colleagues (2018) provides some sweeping insight about how persons of ages >18 years, from different cultures and socioeconomic backgrounds, perceive favorable mental health outcomes with exercise. As shown in Table 1, mental illness is a common problem in the US. The results of this study are most valuable to fitness pros designing exercise programs to promote favorable mental health outcomes.

Table 1. Five Essentials About Mental Health
Mental illness is common in the U.S. Below are some facts from the National Institute of Mental Health.
1) One in five adults (~44.7 million adults) has a mental illness.
2) The two broad categories for mental illness are Any Mental Illness (AMI) and Serious Mental Illness (SMI).
3) The AMI is defined as an emotional, mental, or behavioral disorder. An AMI may vary in impact, ranging from no impairment to mild or moderate impairment. The SMI is defined as a behavioral, mental or emotional disorder resulting in serious functional impairment, which markedly interferes with one or more major life activities.
4) Young adults aged 18-25 years have the highest prevalence of AMI (22.1%) as compared to adults aged 26-49 years (21.1%) and those aged 50 and older (14.5%).
5) Young adults aged 18-25 years have the highest prevalence of SMI (5.9%) compared to adults aged 26-49 years (5.3%) and those aged 50 and older (2.7%).
Source: Mental Illness. (2017). National Institute of Mental Health
Accessed October 6, 2018

@bio:Len Kravitz, PhD, CSCS, is the program coordinator of exercise science at the University of New Mexico, where he received the Outstanding Teacher of the Year and Presidential Award of Distinction. In addition to being a 2016 inductee into the National Fitness Hall of Fame, Len was awarded the 2016 CanFitPro Specialty Presenter Award.

Additional References:
Booth, F.W., Roberts, C.K. & Laye, M.L. (2012). Lack of exercise is a major cause of chronic diseases. Comprehensive Physiology, 2:1143-1211.