1.2 million people can’t be wrong: Exercise linked to fewer ‘bad days’ of mental health

People who exercise report fewer bad days of mental health per month compared with people who don’t exercise, according to a new study of more than 1.2 million Americans published in The Lancet Psychiatry. The beneficial effect of exercise was even greater among people who already had depression, researchers found.

All types of physical activity provided some positive effect, researchers discovered, and people who received the most benefit exercised for about 45 minutes between 3 to 5 times a week.

“Exercise is associated with a lower mental health burden across people no matter their age, race, gender, household income, and education level,” reported investigator Adam Chekroud, PhD, MSc, assistant professor, Department of Psychiatry, School of Medicine, Yale University, New Haven, CT.

Although exercise is already associated with reduced risks for all-cause mortality, cardiovascular disease, stroke, and diabetes, its association with mental health remains unclear. “Because depression is now the leading cause of global disability burden, there is a pressing need to identify modifiable factors that influence mental health burden and which can be the target of population health campaigns to reduce this burden,” Dr. Chekroud and coauthors wrote.

For this cross-sectional study—the largest observational study of its kind to date—investigators analyzed data from 1.2 million US adults who completed the Centers for Disease Control and Prevention Behavioral Risk Factor Surveillance System survey in 2011, 2013, and 2015. Participants reported how many days in the past month that their mental health—including stress, depression, and emotional problems—was “not good.” Participants also reported the frequency and type of activity or exercise, if any, they performed in the past month.

Investigators then compared the number of self-reported bad days of mental health between individuals who exercised and those who didn’t, and adjusted for age, race, gender, marital status, income, education level, body-mass index (BMI) category, self-reported physical health, and previous diagnosis of depression.

Results showed that participants averaged 3.36 days of poor mental health per month. But adults who exercised reported 1.49 fewer days of poor mental health in the prior month than those who didn’t exercise—a 43.2% reduction.

“The effect was larger among individuals who reported a previous depression diagnosis, in whom exercise was associated with a 3.75 day (34.5%) lower mental health burden, than among people who reported a previous diagnosis of depression but did not exercise,” Dr. Chekroud and coauthors wrote.

The association was also observed in individuals who reported no diagnosis of depression, suggesting that the benefit applies to nonclinical populations.

Additional findings:

• The lowest mental health burden was associated with exercising for 30 to 60 minutes (peaking around 45 minutes) 3 to 5 times per week. “This pattern was broadly consistent across all exercise types, and existed for all levels of exercise intensity (light, moderate, or vigorous exercise), with vigorous exercise associated with a more favorable burden than either light or moderate exercise,” the authors wrote.
  
  
• More exercise isn’t necessarily better. In fact, exercising for more than 3 hours a day was associated with worse mental health than not exercising at all. “Previously, people have believed that the more exercise you do, the better your mental health, but our study suggests that this is not the case,” Dr. Chekroud said. “Doing exercise more than 23 times a month or exercising for longer than 90-minute sessions is associated with worse mental health.”
  
  
• Team sports and cycling were associated with the lowest mental health burden, both in the whole population and in individuals with a diagnosis of depression. “Our finding that team sports are associated with the lowest mental health burden may indicate that social activities promote resilience and reduce depression by reducing social withdrawal and isolation, giving social sports an edge over other kinds,” Dr. Chekroud speculated.
  
  
• Mindful exercises (yoga and tai chi) were associated with a significantly lower mental health burden than not exercising (22.9%), but were also linked with a lower health burden than walking (17.4%) or any other exercise (17.8%). “These data suggest that all exercise groups, including social and nonsocial forms, were associated with lower mental health burden,” the authors wrote.
  
  
• Even doing household chores was associated with at least a 9.7% reduction in poor mental health days (about 0.4 days per month).

“Excitingly, the specifics of the regime, like the type, duration, and frequency, played an important role in this association,” Dr. Chekroud said. “We are now using this to try and personalize exercise recommendations, and match people with a specific exercise regime that helps improve their mental health.”

One limitation of the study is that it can’t establish cause and effect between exercise and mental health—and the association may even be bidirectional. “In other words, inactivity might be both a symptom of and contributor to poor mental health, whereas activity might be an indicator of and contributor to resilience,” the authors wrote.

As a follow-up to this study, the researchers plan to collect passive longitudinal data using mobile or wearable sensors (eg, Fitbit), which are not influenced by patient self-reporting. This will allow them to investigate the precise association between the actual frequency, duration, and intensity of exercise and mental health burden.

This research was supported by funding from the Wellcome Trust. Cloud computing resources were provided by Microsoft.