Do you need a new, evidence-based source of to get in shape or stay fit? If so, a recently published seven-year study of over 150,000 people reports that individuals with higher aerobic and muscular fitness levels are significantly less likely to experience and . These findings (Kandola et al., 2020) were published on Nov. 11 in the journal BMC Medicine.
Lead author Aaron Kandola of UCL's Division of and colleagues found that people with low levels of cardiorespiratory and muscular fitness were almost twice as likely to experience depression than study participants with higher aerobic/muscular fitness. Low levels of fitness also predicted a significantly greater chance of . Karmel Choi of Harvard Medical School, whose previous research (Choi et al., 2019) found that physical activity keeps depression at bay, is a co-author of this study.
This prospective cohort study involved 152,978 participants age 40 to 69 who were part of the more extensive UK Biobank Study, consisting of 500,000 people from England, Scotland, and Wales recruited between April 2007 to December 2010 to participate in nationwide longitudinal research.
About seven years ago, Kandola et al. collected baseline measurements of participants' cardiorespiratory fitness using stationary bicycles and conducted grip strength tests using a hydraulic hand dynamometer in each hand as a predictor of total muscle strength.
At baseline, the researchers accounted for confounding factors such as , dietary habits, mental illness history, and socioeconomic status. Participants also filled out questionnaires that assessed depression and anxiety symptoms.
Seven years later, the researchers conducted the same tests again and found that "high aerobic and muscular fitness at the start of the study was associated with better mental health seven years later."
More specifically, the follow-up analysis showed that "people with the lowest combined aerobic and muscular fitness had 98% higher odds of depression, 60% higher odds of anxiety, and 81% higher odds of having either one of the common mental health disorders, compared to those with high levels of overall fitness." (Note: This is an observational study that identifies correlation, not causation.)
Based on these findings, the authors speculate that aerobic and resistance training may offset the risk of experiencing depression, anxiety, and other common mental health disorders. "While broadly increasing physical activity will be beneficial, structured aerobic and resistance exercises with sufficient intensity to improve fitness may have a greater effect on risk reduction," the authors note.
"Our findings suggest that encouraging people to exercise more could have extensive public health benefits, improving not only our physical health but our mental health too," senior author Joseph Hayes of University College London said in a news release. "Improving fitness through a combination of cardio exercise and strength and resistance training appears to be more beneficial than just focusing on aerobic or muscular fitness."
"Other studies have found that just a few weeks of regular intensive exercise can make substantial improvements to aerobic and muscular fitness, so we are hopeful that it may not take much time to make a big difference to your risk of mental illness," Kandola added. "Reports that people are not as active as they used to be are worrying, and even more so now that global lockdowns have closed gyms and limited how much time people are spending out of the house. Physical activity is an important part of our lives and can play a key role in preventing mental health disorders."
From a public health perspective, the researchers speculate that encouraging the general population to improve their physical fitness through a combination of cardio workouts and strength-training exercises could significantly reduce the incidence of depression, anxiety, and other common mental disorders while simultaneously improving physical health outcomes.