STUDY REVIEWED: Chekroud, S.R., 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, 5 (9), 739–46.
Exercise has proven benefits for improving physical health. But what about mental health? For starters, active people are nearly 45% less likely to have depressive symptoms than inactive people (Booth, Roberts & Laye 2012). But a deeper look at the connections between exercise and mental health raises complicated questions:
- How do factors such as frequency, duration and intensity of exercise relate to mental health?
- Are all types of exercise equally effective and beneficial for mental health?
- At what point does exercise become harmful to mental health?
Recent research by Chekroud et al. (2018) sheds new light on these questions. The results provide critical insights for fitness pros who want to design programs to ease clients’ mental health burdens.
Methods: Survey and Mental Health Questions
Chekroud and colleagues examined data from more than 1.2 million U.S. adults who answered the Centers for Disease Control and Prevention’s Behavioral Risk Factor Surveillance System survey in 2011, 2013 and 2015. To identify people dealing with mental health issues (see “Three Essential Facets of Mental Health”), the survey included this question:
“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?”
Respondents who said yes were asked: “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: Physical Activity Data
To link mental health with exercise, the survey asked, “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 yes response prompted this follow-up: “What type of physical activity or exercise did you spend the most time doing during the past month?”
The researchers identified 75 types of exercise which they grouped into eight categories to help the participants specify their physical activities: walking, popular sports, cycling, aerobic or gym workouts, running or jogging, recreational, household, and winter or water sports. Survey respondents reported the number of times per week or month they did each type of exercise and the length of a typical session in minutes or hours.
Using a variety of complex statistical measures, the researchers broke new ground in clarifying several questions regarding exercise and mental health. The following question-and-answer format summarizes their findings.
1. HOW EFFECTIVE IS EXERCISE IN MANAGING MENTAL HEALTH PROBLEMS?
An analysis of 852,068 adults (out of 1.2 million surveyed) associated exercisers with 43.2% fewer self-reported mental health burdens per month than nonexercisers. The study observed this correlation across all ages, racial groups and household income levels.
2. ARE ALL TYPES OF EXERCISE ASSOCIATED WITH IMPROVED MENTAL HEALTH?
Yes. Doing any type of exercise is associated with fewer mental health burdens compared with not exercising. In the study, the strongest correlations were for popular sports (22.3% fewer), cycling (21.6% fewer), and aerobic and gym exercises (20.1% fewer). An exploratory analysis conducted after the main study found that mindful exercises such as yoga and tai chi were associated with a 22.9% reduction in mental health burdens.
3. IS THERE AN OPTIMAL EXERCISE SESSION DURATION FOR IMPROVING MENTAL HEALTH BURDENS?
Yes. Exercise sessions lasting between 30 and 60 minutes correlated with the fewest mental health burdens—45 minutes produced the best effect consistently across all exercise types. Sessions longer than 90 minutes proved less effective. Indeed, exercising for more than 3 hours per session was associated with greater mental health burdens than not exercising at all.
4. IS THERE AN OPTIMAL EXERCISE FREQUENCY FOR REDUCING MENTAL HEALTH BURDENS?
Yes. Survey respondents who exercised 3–5 times a week had fewer mental health burdens than those who exercised less than 3 times or more than 5. This pattern persisted across all exercise types for light, moderate and vigorous intensities.
5. IS ANY SPECIFIC EXERCISE INTENSITY ASSOCIATED WITH MORE FAVORABLE DECREASES IN MENTAL HEALTH BURDENS?
Yes. The study found that vigorous exercise was linked to better mental health outcomes than either light or moderate exercise.
Assessing the Role of Exercise in Mental Health
Chekroud et al. is the largest cross-sectional study to investigate the effects of exercise on mental health. While exercisers report fewer mental health problems than nonexercisers, always keep in mind what works—and what doesn’t:
- Exercise sessions of 30–60 minutes provide the best outcomes; 45 minutes is optimum. Harder intensities provide better mental health results.
- Exercising at least 3–5 times a week in a variety of modes is appropriate for producing mental health benefits.
- More exercise is not necessarily better. Among survey respondents, exercising more than 23 times per month or longer than 90 minutes per session was associated with worse mental health outcomes than not exercising at all.
- Popular sports—mostly team competitions—correlate with the fewest mental health burdens. The researchers said this finding aligns with previous studies showing that social activity reduces depression and promotes a hardiness in relation to stress. These results suggest favorable stress effects for people involved in group exercise, given that it’s a social activity. More research on this hypothesis is warranted.
Booth, F.W., Roberts, C.K. & Laye, M.L. 2012. Lack of exercise is a major cause of chronic diseases. Comprehensive Physiology, 2 (2), 1143–211.
NIMH (National Institute of Mental Health). 2017. Mental Illness. Accessed Oct. 6, 2018: nimh.nih.gov/health/statistics/mental-illness.shtml.