Cardiorespiratory health and muscular fitness might play an important role in common mental disorders, according to a new study published in BMC Medicine. The research indicates that people with low levels of fitness are more likely to suffer from anxiety and nearly twice as likely to experience depression.
“Physical fitness is a critical marker of physical health but we know relatively little about its relationship with mental health. If fitness is related to mental health, it strengthens these emerging ideas we are seeing now about the interrelationship between physical and mental health,” said study author Aaron Kandola, PhD candidate at University College London’s Division of Psychiatry.
“We know physical activity is broadly beneficial, but we know little about what types of activities and at what intensity are most helpful for mental health. For example, if we know muscular fitness is associated with good mental health, we know improving muscular fitness involves consistent resistance training and a gradually increasing intensity several times a week over the course of a few weeks.”
Previous studies have found that people who exercise more are less likely to experience mental illnesses, but most studies rely on people self-reporting their activity levels, which can be less reliable than the objective measures.
“Physical activity is a behavior and complex to measure or interpret. Fitness is a biological trait and pretty straightforward to measure objectively with tests and interpret the outcome,” Kandola said.
For their new study, the researchers analyzed data from 152,978 individuals aged 40 to 69 who participated in the UK Biobank study. Their baseline aerobic fitness at the start of the study period was tested by using a stationary bike with increasing resistance, while their muscular fitness was measured with a grip strength test. The participants also completed a questionnaire gauging depression and anxiety symptoms.
Seven years later, the participants again completed assessments of depression and anxiety symptoms, and the researchers found that high aerobic and muscular fitness at the start of the study was associated with better mental health seven years later.
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.
“Maintaining good fitness is important for both physical and mental health. Try to combine different activities into a routine to keep multiple aspects of fitness at a good level i.e. resistance and cardio exercises to keep muscular and aerobic fitness levels up,” Kandola told PsyPost.
“The real danger is low fitness – people with low fitness had the worst mental health outcomes in our study. People with low fitness should start slow, keep the exercises simple, build up over time, don’t rush into intense aerobic or resistance training regimes.”
The researchers accounted for potentially confounding factors at baseline such as diet, socioeconomic status, chronic illness, and mental illness symptoms. But as with any study, the new research includes some limitations.
“Our study was observational, we looked at people’s fitness and mental health over time – but we didn’t experimentally change anything ourselves. It is important that trials build on this evidence to clearly demonstrate cause and effect. There are quite a few trials showing exercise is good for depression and anxiety symptoms, but they don’t usually focus on improving fitness specifically,” Kandola explained.
The study, “Individual and combined associations between cardiorespiratory fitness and grip strength with common mental disorders: a prospective cohort study in the UK Biobank“, was authored by Aaron A. Kandola, David P. J. Osborn, Brendon Stubbs, Karmel W. Choi, and Joseph F. Hayes.