Individuals who exercise regularly have superior mental health compared to those who do not exercise, new research suggests.
Investigators studied data for 1.2 million US adults and found that those who exercised had 1.5 fewer days of poor mental health during the past month than their physically inactive matched counterparts.
Amid the wide range of activity included in the study, team sports, cycling, aerobics, and going to the gym were associated with the largest reductions.
The regimen associated with the greatest benefits was exercising for 45 minutes three to five times a week.
"I think for clinicians, this study continues to reiterate the benefits of exercise for mental health, as well as physical health," lead author Adam Chekroud, assistant professor of psychiatry, Yale University, New Haven, Connecticut, and chief scientist at Spring Health, told Medscape Medical News.
"For larger health systems or service-providing enterprises like Spring Health, this research is particularly important because it helps us understand that exercise might be an important modifiable factor to help improve mental health burden, regardless of age, gender, socioeconomic background, or physical health status," he added
The study was published online August 8 in Lancet Psychiatry.
Host of Physical Benefits
"Physical exercise is associated with several positive health benefits.... Research into the effect of exercise on mental health has provided conflicting results," the authors write.
The authors suggest that a potential reason for inconsistent findings is the use of small or nonrepresentative samples.
"I know that personally, I have a really strong relationship between how I'm feeling mentally and how often I was going out for bike rides," Chekroud recounted.
"From the academic perspective, we know that exercise has a whole host of physical benefits, and from the perspective of our mental health startup, Spring Health, we know a lot of people don't feel ready or comfortable starting treatment for mental health conditions and usually want to try out other self-help style options first," he continued.
"I had read smaller-scale studies in the past showing that exercise was an effective antidepressant, and I wanted to explore this further and really try to understand what kinds of exercise might be most beneficial, and how long or how often I'd need to be doing it — that kind of information just wasn't really made compelling in the literature," he said.
To investigate the question, the researchers analyzed data from the Behavioral Risk Factor Surveillance System survey collected by the Centers for Disease Control and Prevention (CDC), relating to individuals aged 18 years or older in all 50 states between 2011 to 2015.
Participants were asked to respond to several questions, including whether they had been previously diagnosed with depression or a depressive episode; how many days during the past 30 days their mental health was "not good"; whether they had exercised during the past month and, if so, what type of exercise they spent the most time doing.
Participants reported the number of times per week or month that they engaged in the exercise and the number of minutes or hours that they usually spent exercising.
The full covariate set consisted of age, race, sex, marital status, income, education level, employment status, body mass index category, self-reported physical health, and previous diagnosis of depression.
More Not Necessarily Better
The final sample consisted of 1,237,194 participants. The mean mental health burden of poor mental health in the past month was 3.36 days (SD, 7.7; median 0; IQR, 0 - 2).
Analysis of 852,068 matched individuals (73.6% of whom exercised) found that exercise was associated with a 1.49-day (43.2%) lower self-reported mental health burden per month (W = 7.42×10-10, P < 2.2×10-16) for individuals who exercised vs those who did not.
The researchers repeated the same analysis specifically for matched individuals with and without a previous depression diagnosis and found that the effect was larger among those who reported a previous depression diagnosis.
The association between exercise and mental health burden was found across the full age span, among both sexes, for all racial groups, and with regard to all levels of household income.
All types of exercise were associated with a reduction in mental health burden (minimum reduction of 11.8%, P < 2.2×10-16 for all exercise types), compared with no exercise.
There were, however, differences with respect to exercise type. The strongest associations were found for popular sports, cycling, and aerobic and gym exercises (22.3%, 21.6%, and 20.1% lower, respectively).
Even engaging in household chores was associated with a reduction of ≥9.7% in days of poor mental health (approximately 0.4 days per month).
An exploratory post hoc analysis found that mindfulness-oriented exercises (yoga and tai chi) were associated with a significantly greater reduction in mental health burden than not exercising (22.9%), walking (17.4%), or engaging in any other exercise (17.8).
When controlling for the full covariate set, the researchers found exercising for a period of 30 to 60 minutes (peaking around 45 minutes) was associated with the lowest mental health burden.
This pattern of optimal duration was "broadly consistent" across many exercise types. Smaller reductions were seen in individuals who exercised for longer than 90 minutes.
Exercising for longer than 3 hours was associated with worse mental health burden than exercising for either 45 minutes or not exercising at all.
For people who exercised between three and five times a week, mental health burden was lower than for those who exercised either less than 3 or more than 5 times weekly.
"I would say I was pleasantly surprised by the findings, for sure," Chekroud commented.
"It was really encouraging to see that even relatively accessible exercises were associated with better mental health — things like just walking three times a week."
He noted that this "is important because previous research was focusing on quite demanding kinds of exercise, like resistance training, which might not be accessible to a large portion of the population."
It also came as a surprise that "the concept of 'more exercise is better' didn't really hold up — in fact, it seemed like people who exercise for very long durations or over 22 times per month were having more days of bad mental health than people who didn't exercise," he observed.
Largest Study to Date
Commenting on the study for Medscape Medical News, Gary Cooney, MBChB, MRCPsych, registrar in psychiatry, Gartnavel Royal Hospital, Glasgow, United Kingdom, who was not involved in the research, said that to his knowledge, this is "the largest study examining the association between health and exercise/physical activity."
The "biggest contribution the study will make to the field is to highlight the importance of this area and hopefully encourage more specific studies examining types of exercise and their associations with outcomes for specific mental disorders," said Cooney.
However, he expressed reluctance to "identify any particular take-home messages for practicing clinicians from the study" because he had "some reservations about the methodological approaches."
His reservations, which he expressed in an accompanying editorial, include the researchers' "combining of all mental disorders into a single entity," coupled with "repeated contextualization of this study with major depressive disorder," which implies an "uncomfortable interchangeability between mental health and depression."
Cooney also expressed concern regarding the unreliability of self-report and the definition of exercise (ie, inclusion of an array of activities that may not fulfill the definition of exercise, as offered by the American College of Sports Medicine).
He noted that this is "a really difficult field for research because, by nature, it is impossible to blind participants to bias."
He suggested "optimizing the scientific rigor by including, for instance, the use of validated outcome measure tools, the use of interview/questionnaires to confirm diagnosis, and the avoidance of 'umbrella terms,' such as 'mental health' and 'exercise,' where exercise is not clearly defined."
Dr Chekroud added, "Moving forward, we're excited to build on this research as part of our personalized psychiatry program and offer our patients personalized exercise regimes to help improve their mental health."
Dr Chekroud and Dr Cooney have disclosed no relevant financial relationships. Financial disclosures for Dr Chekroud's coauthers are listed in the original article.
Lancet Psychiatry. Published online August 8, 2018. Abstract
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Cite this: More Evidence Exercise Improves Mental Health - Medscape - Aug 13, 2018.
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