Previous studies have shown that a sedentary lifestyle increases the risk of depression, but most of these have been based on interviews with adults.
Researchers from the University of Gothenburg’s Sahlgrenska Academy can now show in a large-scale study that exercise while young is linked to a reduced risk of serious depression later in life.
“The teenage years are a critical period in the development of the brain when higher functions are established and social and emotional skills develop,” explains Maria Åberg from the Sahlgrenska Academy, the researcher who led the study.
“There was therefore a need for wider studies of younger people.”
The study covers all Swedish men born between 1950 and 1987 in good mental health on enlisting for military service, which was then compulsory. For these 1,117,292 men, the researchers compared the results of physical tests at the time of enlistment with national disease registers.
“Poor physical fitness at the age of 18, as measured by test results on an exercise bike on enlisting, was directly associated with an increased risk of serious depression in adult years,” says Maria Åberg.
“Separate analyses were performed to allow for reverse causality – in other words the possibility of very early symptoms of depression leading to reduced fitness in the physical tests. But even after taking this into account, there were still the same associations. Even more remarkable is that the increase in risk could be observed up to 40 years later.”
By undertaking a special analysis of the roughly 380.000 brothers covered by the study, the researchers were also able to rule out environmental and hereditary factors.
Maria Åberg and her research group have shown in a previous study that high levels of fitness as a teenager impact on IQ and academic performance, and she thinks that schools should give sport a higher status and more resources.
“While there’s a need for more research in this area, our results provide strong support for school curricula including more active sporting activity and encouraging habits that build and maintain physical fitness.”
The article “Cardiovascular fitness in males at age 18 and risk of serious depression in adulthood: a Swedish prospective population-based study” was published in the British Journal of Psychiatry on June 14 2012.