Researchers have reported a clear link between poor physical fitness and the risk of exhibiting symptoms of depression, anxiety, or both.
The study, which included more than 150,000 participants, found that cardiorespiratory fitness and muscle strength independently contribute to a greater risk of deteriorating mental health.
However, the researchers saw the most significant association when they looked at the combination of cardiorespiratory fitness and muscle strength.
The research, published in the journal BMC Medicine, may help inform clinical advice on mental health and fitness.
Mental health issues, just like physical health issues, can have a significant negative effect on a person’s life. Anxiety and depression are two of the most common mental health problems.
There is a growing body of evidence that physical activity can help prevent or treat mental health problems. However, there are still many questions that need answers.
For example, what metrics should researchers use to quantify physical activity? In what ways can it prevent mental health problems or improve a person’s mental health? And is it possible to demonstrate a causal link between physical activity and better mental health?
It is important to have detailed evidence of the relationship between physical activity and mental health, as well as the mechanisms that may underlie it. With this information, clinicians can offer more targeted counseling to people with mental health problems.
To begin to answer some of these questions, a team of researchers analyzed a large body of existing data that allowed them to strengthen their understanding of the association between fitness and mental health.
In the present study, the researchers relied on data from UK Biobank, a data repository comprising information from more than 500,000 volunteers aged 40 to 69 from England, Wales and Scotland. .
Between August 2009 and December 2010, a subset of UK Biobank participants – 152,978 participants – underwent tests to measure their physical condition.
Investigators assessed participants’ cardiorespiratory fitness by monitoring their heart rate before, during, and after a six-minute submaximal stress test on a stationary bike.
They also measured the volunteers’ grip strength, which the researchers in the present study used as an indicator of muscle strength. Along with these fitness tests, participants completed two standard clinical questionnaires related to anxiety and depression to give researchers insight into their mental health.
After seven years, the researchers again assessed each person’s anxiety and depression using the same two clinical questionnaires. In their analysis, the researchers took into account potential confounding factors, such as age, birth sex, previous mental health issues, smoking, income level, physical activity, school experience. , parental depression and diet.
Researchers found a significant correlation between participants’ initial fitness and mental health seven years later.
Participants who were classified as having low combined cardiorespiratory capacity and low muscle strength were 98% more likely to experience depression and 60% more likely to experience anxiety.
The researchers also looked at the distinct correlations between mental health and cardiorespiratory fitness, and mental health and muscle strength. They found that each fitness measure was individually associated with a change in risk, but less significantly than the combination of measures.
According to Aaron Kandola, the lead author of the study and a doctoral candidate in the Division of Psychiatry at University College London, UK: âHere we have provided further evidence of a relationship between physical health and mental health and this structured exercise aimed at improving different types of fitness is not only good for your physical health, but may also have beneficial effects on mental health.
The study is a robust prospective study with a long follow-up period of seven years and objective measures of risk factor (cardiovascular fitness and muscle strength) and outcome (depression, anxiety or both).
While it does demonstrate a correlation between fitness and better mental health outcomes, that doesn’t necessarily mean there is a causal relationship between the two. For example, it could be that people with better mental health are more likely to stay physically active.
However, researchers have deployed various statistical techniques that they believe suggest there is likely a causal relationship between fitness and better mental health.
In addition to adjusting for potential confounders associated with both low levels of fitness, depression, and anxiety, such as smoking, the authors also performed a number of sensitivity analyzes.
They checked for reverse causality (when the result is actually the cause) by excluding people who were depressed or anxious at the start of the study. They also changed the cut-off values ââthat determined whether people suffered from depression. None of these analyzes changed their conclusions.
It remains to show the mechanisms that could explain this relationship.
Nevertheless, the results are still important. In addition to providing additional evidence for the beneficial effects of physical activity on mental health, the study is also one of the first to use objective measures of fitness to do so.
For researchers, this could mean that quantitative measures of physical fitness and, in particular, measures of cardiorespiratory fitness and muscle strength – rather than self-reports of physical activity – could potentially serve as indicators. of mental health risk for clinicians.
Encouragingly, the researchers note that a person can significantly improve their fitness in as little as three weeks. According to their figures, it can reduce the risk of developing a common mental health problem by up to 32.5%.
For Kandola, the results are particularly relevant given the effects of the current COVID-19 pandemic.
“Reports that people are not as active as they used to be is worrying, and even more so now that global lockdowns have closed gyms and limited the time people spend away from home,” Kandola said. âPhysical activity is an important part of our life and can play a key role in preventing mental health problems. “