New research tracking Norwegian youth for over a decade shows that getting more active in your mid-teens can significantly lower your risk of depression, revealing the real power of movement for mental health.
Study: Symptoms of Depression, Physical Activity, and Sedentary Time: Within-Person Relations From Age 6 to 18 in a Birth Cohort. Image Credit: oneinchpunch / Shutterstock
A research team at the Norwegian University of Science and Technology followed a large group of children and adolescents from age 6 to 18 and found that young adolescents who increase their physical activity from the age of 14 have a lower risk of developing depression later in life. The study is published in the Journal of the American Academy of Child & Adolescent Psychiatry.
Background
A significant increase in the prevalence of major depressive disorder has been observed among young people in the last decade. The childhood to adolescence transition period is particularly sensitive for the development of mental disorders, including depression.
Physical activity is a promising preventive intervention for mental health and overall well-being. However, increasing physical activity as an intervention to prevent depression in children and adolescents has shown only a modest effect in the short term. This highlights the need for more research with a more extended follow-up period.
The majority of observational studies aim at understanding whether a child with a higher level of physical activity will have less depression than other children with a lower level of physical activity. This kind of cross-sectional analysis (“between-person” comparison), however, cannot accurately assess the risk of depression.
Longitudinal comparisons that compare changes occurring within an individual over time (“within-person” comparison) provide more precise information for planning a treatment or developing a preventive intervention.
Given the significant impact of physical activity on mental health, researchers designed this study to explore “within-person” relationships between physical activity, sedentary time, and depressive symptoms. They included sedentary time in the analysis as it is a vital parameter to predict health, irrespective of physical activity. The use of within-person analyses in this study allowed the researchers to control for all stable, unmeasured confounders, providing more robust findings than traditional between-person comparisons.
Study design
The study analyzed data from 873 participants in the Trondheim Early Secure Study, a cohort study of children born in Trondheim, Norway, in 2003 and 2004. The participants were followed from age 6 to 18.
The participants' physical activity was assessed using an accelerometer every two years, and clinical interviews were conducted to determine their mental health. The study analyzed seven rounds of data (6, 8, 10, 12, 14, 16, 18 years) collected from them.
“We also investigated whether belief in one’s own physical abilities, body image, and sports participation had an impact on the association between physical activity and depression,” said Professor Silje Steinsbekk, Department of Psychology at Norwegian University of Science and Technology.
Study findings
The study revealed that adolescents aged 14 to 18 years (middle to late adolescence) who have a lower level of physical activity are at higher risk of developing depressive symptoms two years later. This association was similar for male and female participants.
However, the study could not find any association between sedentary time and depressive symptoms. Regarding the opposite direction of influence, the study found that an increased number of depressive symptoms predicts decreased levels of physical activity from ages 10 to 12 and 14 to 16.
Importantly, the study tested whether factors such as athletic self-esteem, body image, or sports participation explained the relationship between physical activity and depressive symptoms. However, the researchers found that none of these factors mediated the association.
Study significance
The study reveals that young people who increase their physical activity level from the age of 14 years are at lower risk of developing depressive symptoms later in life. While the protective association was found only from age 14 onward, the difference in effect size compared to earlier ages was not statistically significant. However, a similar benefit of physical activity has not been observed at earlier ages.
“This finding was true for teens 14 to 16 years old and 16 to 18. Both the sum of daily physical activity and the proportion of activity that is more intense and particularly important for our health turned out to protect against symptoms of depression,” Steinsbekk said.
In younger age groups, the study finds that participants who experience more depressive symptoms are more likely to have lower levels of physical activity.
“Although we found that physical activity seems to protect against depression symptoms in adolescence, this did not apply to young adolescents aged 10–14. However, we found an opposite correlation from 10–12 and 14–16 years: Those who had more symptoms of depression were more likely to become less physically active,” Steinsbekk said.
The study could not find any association between time spent in sedentary activity and the risk of depressive symptoms, highlighting that sedentaryness is not just the opposite of physical activity. Physical activity is associated with a sense of accomplishment, self-esteem, neurophysiological effects, social interactions, companionship, and belongingness, which collectively contribute to an individual's physical and mental well-being.
As mentioned by researchers, these findings cannot be generalized to clinical samples of adolescents with depression, as the association between physical activity and depression is stronger in clinical samples. Similarly, these findings may not be generalized to other populations, as the prevalence of mental health problems is lower in Norway, and Norwegian children are reportedly more physically active than other European children.
It is also worth noting that the effects found in this study were of moderate size, and although they may accumulate over time, many factors influence whether young people develop depressive symptoms.
Overall, the study suggests that interventions aimed at increasing physical activity among young people may help prevent the development of depressive symptoms.