Money can’t buy happiness—but exercise can?

By Naveed Saleh, MD, MS, for MDLinx
Published June 5, 2019

Key Takeaways

Getting regular exercise may actually make you happier than having greater wealth, according to researchers from Yale and Oxford who published findings from their study in Lancet Psychiatry.

Specifically, individuals who exercised regularly had about 18 fewer days of poor mental health annually compared with those who did not exercise. The investigators also found that, in addition to having a greater sense of well-being, physically active individuals felt as good as non-active people who earned $25,000 more in annual income.

“The difference in mental health burden between individuals who participated in popular (team-based) sports versus those who do not exercise was approximately the same as the difference in mental health burden between individuals…with a difference in household income of more than US$25,000,” wrote the authors, led by Sammi R. Chekroud, Oxford Centre for Human Brain Activity, Wellcome Centre for Integrative Neuroimaging, Department of Psychiatry, University of Oxford, Oxford, United Kingdom.

Exercise does a body good

Although all clinicians know that exercise does a body good, surprisingly little research has been done on the effect of exercise on mental health burden. Thus, researchers conducted this cross-sectional study to investigate this association. They mined data representing over 1.2 million US adults from the 2011, 2013, and 2015 Centers for Disease Control and Prevention Behavioral Risk Factors Surveillance System surveys, and analyzed the effects of exercise type, duration, frequency, and intensity on mental health burden.

The authors compared self-reported “bad” mental health between individuals who exercised with those who did not by asking the following 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?”

Participants were also asked whether they engaged in any physical activity or exercise besides their regular jobs. Those who responded positively were then queried on the type of physical activity or exercise they spent the most time doing in the previous month. In all, 75 types of exercise were represented in the sample, from lawn-mowing and housework to weight-lifting and cycling.

The researchers controlled for sex, marital status, education level, income, body mass index category, self-reported physical health, and previous diagnosis of depression, and performed manifold sensitivity analyses.

Exercise linked to less ‘bad’ mental health

Exercisers had a 1.49 (43.2%) reduction in bad mental health days during the past month vs non-exercisers, who were otherwise matched for physical and sociodemographic characteristics. This reduction translated to about 18 fewer poor mental health days per year, and this correlation was strongest among subjects who exercised 3-5 times per week at 30-60 minutes per session.

In people who reported a previous diagnosis of depression, the effect was even larger. Compared with people with depression who didn’t exercise, those who did exercise had 45 fewer bad mental health days per year.

Any type of exercise was associated with a lower mental health burden compared with no exercise. Playing team sports—alternatively defined as “popular sports,” with no examples given by the authors—was associated with the largest reduction, 22.3%. Large reductions were also found for cycling, 21.6%, and for aerobic and gym activities, 20.1%. Even walking was associated with a 17.7% reduction in mental health burden compared with no exercise.

However, the researchers found that more time spent exercising wasn’t always better in terms of mental health. In fact, people who exercised more than 23 times per month, or for more than 90 minutes per session, exhibited worse mental health.

Effects of exercise were sizeable when compared with other modifiable factors. For example, the mental health burden in subjects who took part in team sports vs those who did not was about the same as the difference in mental health burden of having a college degree vs high school degree, or a difference in annual household income of more than $25,000.

The positive effects of exercise are, indeed, manifold and include decreased overall mortality, enhanced musculoskeletal health and stress regulation, and lowered risks of cardiovascular disease, obesity, stroke, and cancer. Nevertheless, other research on the effect of exercise on mental health burden has yielded limited and sometimes conflicting results.

In some randomized controlled trials, for instance, experts have shown that exercise is an effective treatment for mild and moderate depression, either alone or in combination with other treatments. Yet, these studies have either been of low power, have included non-representative or small samples, have included few exercise types, and/or have failed to consider other features of exercise (eg, duration and frequency).

With respect to the current study, the authors concluded that: “These findings could offer a platform for future research into the role of exercise in reducing mental health burden in a more efficient manner both in randomised clinical trials and at a population level.”

More exercise is not better

In a commentary published in the Journal of Sport and Health Science, Dr. Anne-Marie Elbe, Institute of Sport Psychology and Physical Education, Faculty of Sport Science, Leipzig University, Leipzig, Germany, and colleagues were impressed with the current study, writing:

“A very interesting aspect of the study of Chekroud et al is that it contributes to our knowledge about the optimal range for frequency and duration of physical exercise and that it is not a ‘the more, the better’ relationship. Chekroud et al. show that the correlation with mental health burden was lowest when individuals engage in about 45 min of exercise 3-5 days per week. This is in close agreement with the recommendation of 150 min per week of moderate-to-vigorous physical activity from the World Health Organization.”

Dr. Elbe and coauthors did, however, did discuss limitations of the study, including those that contradicted their position that mental health exists on a continuum, and not in a dichotomous state, as promoted by Chekroud et al: “The measurement of mental health is based on 1 item that asks participants how many days during the past 30 days their mental health was not good. Assessing mental health in this way is quick and effective, but it does not reflect the fact that mental health is currently described as a continuum.”

Finally, they noted that the cross-sectional nature of the study renders it unclear with respect to the direction of causality between exercise and mental health.

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