Although there is evidence that exercise can boost mental health, scientists know less about whether physical fitness can prevent the onset of mental health conditions. A recent systematic review and meta-analysis take a closer look.

Common mental health problems, such as depression and anxiety, are a growing global issue.

They reduce overall wellbeing and life satisfaction, but they may also increase the risk of cardiovascular disease and increase mortality risk.

Although talking therapies and medication can help in many instances, they do not help everyone.

An issue as substantial as mental health needs an effective public health strategy; stopping mental health issues before they begin would, of course, be ideal.

Researchers are focused on unraveling the myriad of factors that increase the risk of developing mental health conditions. Although it is not possible to alter some of these factors, such as genetics, it is possible to modify some lifestyle factors, including diet and physical activity.

Scientists are keen to identify which modifiable factors might have the most significant impact on mental health. Some researchers are looking to physical fitness.

Fitness and mental health

The authors of a recent study investigated whether cardiorespiratory fitness might be an effective intervention. Cardiorespiratory fitness is a measure of the cardiovascular and respiratory systems' capacity to supply oxygen to the body during exercise.

They recently published the results of their analysis in the Journal of Affective Disorders.

The authors explain how previous studies "have found that low physical activity is associated with a greater incidence of common mental health disorders." However, few studies have investigated whether cardiorespiratory fitness is directly related to mental health risk.

Medical News Today spoke with the lead author of the study Aaron Kandola, from University College London in the United Kingdom. We asked him why so few studies have looked at this question.

One reason, he said, is that cardiorespiratory fitness "can be expensive and impractical to measure, particularly in large groups of people." He explains how it needs to be "measured with structured exercise tests that require the use of specialized equipment in a controlled environment."

A small pool of studies

To investigate, the researchers hunted down studies that looked at how fitness interacts with mental health risk.

They only included papers that used a prospective study design. This means that at the beginning of the studies, none of the participants had mental health conditions, and researchers observed them for a time to see if any mental health issues arose.

All experiments assessed cardiorespiratory fitness and either depression or anxiety.

In total, the researchers only identified seven studies to include in their qualitative synthesis and four that they could enter into their meta-analysis.

Their analysis of the latter four studies — which included 27,733,154 person-years of data — produced significant results. The authors write:

"We found that low [cardiorespiratory fitness] and medium [cardiorespiratory fitness] are associated with a 47% and 23% greater risk of [...] common mental health disorders, compared with high [cardiorespiratory fitness]."

They also found evidence of a dose-dependent relationship between fitness and common mental health conditions. The authors explain that "[i]ncremental increases in [the cardiorespiratory fitness] group were associated with proportional decreases in associated risk of new onset common mental health disorders."

The results were in line with the researchers' expectations. As Kandola told MNT, "exercise is the biggest determinant of cardiorespiratory fitness," and scientists have already uncovered "the benefits of exercise for common mental health disorders."

However, he explained that they "were surprised at the lack of research in this area." He hopes that their study will "help to draw more attention to it."

Kandola plans to continue exploring this avenue. He told MNT that the team is "currently working on several other studies to further investigate the impact of exercise and fitness on mental health across the lifespan, and to identify possible mechanisms that underlie this relationship."