Originally published Feb. 11, 2020 by CNN Health.
By Sandee LaMotte
Science shows moderate to vigorous aerobic exercise is good for us — it improves sleep; lowers blood pressure; protects against heart disease, diabetes and cancer; reduces stress; boosts mood; and fights anxiety and depression.
It’s especially important in adolescence, where the first signs of depression often begin, studies show. But unless your child is an athlete, it can be tough to wean them away from social media and the ever-present screen to swim laps or go for a blood-pumping jog. A new study has some good news: even light exercise may help protect children against developing depression.
The study, published Tuesday in the journal Lancet Psychiatry, found that 60 minutes of simple movement each day at age 12 was linked to an average 10% reduction in depression at age 18. The types of movement ranged from running and biking to walking, doing chores, painting or playing an instrument.
“It’s not just more intense forms of activity that are good for our mental health,” Aaron Kandola, a PhD student in psychiatry at University College London and lead author of the study, said in a statement.
“A lot of initiatives promote exercise in young people, but our findings suggest that light activity should be given more attention as well,” senior author Dr. Joseph Hayes, a psychiatrist and clinical research consultant at University College London, said in a statement.
“Schools could integrate light activity into their pupils’ days, such as with standing or active lessons,” Hayes said. “It doesn’t require much effort and it’s easy to fit into the daily routines of most young people.”
The study used information from the University of Bristol’s Children of the ’90s study, which has been following 14,500 women and their children for 30 years, from pregnancy onward.
As part of this, 4,257 adolescents wore instruments to track their movements at ages 12, 14 and 16 over a three-day period. For at least 10 hours each day, accelerometers recorded whether the child moved or was sedentary. The machines provided a better method of tracking than prior studies, which relied on self-reporting, researchers said.
“Worryingly, the amount of time that young people spend inactive has been steadily rising for years, but there has been a surprising lack of high-quality research into how this could affect mental health,” Kandola said.
Sedentary behavior increased as the children grew older, the study found, with depression scores highest among the least active. Each additional hour of sitting at age 12 was linked to an 11% increase in depression scores at age 18, based on a clinical questionnaire that measures depressive symptoms and their severity on a spectrum.
At age 14, each additional hour of being inactive raised depressive scores by 8%, while 16-year-olds had an increased score of 10.5%, the study found. The study only looked at depression, not anxiety disorders.
Researchers adjusted their analysis to account for those with depression at the beginning of the study as well as socioeconomic status, parental history and the like, which are all linked to mental health. While the study is only an association and can’t prove a relationship between movement and depression, “our study suggests that these two trends may be linked,” Kandola said.
In fact, the data “suggested that a 2 reduction in daily sedentary behavior between the ages of 12 and 16 years old was associated with a 16 22% reduction in depression scores by age 18,” the study said.
Rates of adolescent mental disorders on rise
According to the World Health Organization, depression is one of the leading causes of illness and disability among adolescents around the world, accounting for “16% of the global burden of disease and injury in people aged 10 to 19 years.”
In the United States, rates of teen depression are on the rise. A new study to be published in March found rates of major depressive episodes in the last year among teens increased 52% between 2005 and 2017. The study analyzed data from the US National Survey on Drug Use and Health and found rates rose from 8.7% to 13.2% over that time span.
A depressive episode is defined by a list of symptoms that include feeling sad, hopeless, frustrated, anxious or worthless for at least two weeks.
That number fits with a 2017 analysis by the US National Institute of Mental Health, which found 13.3% of American teens aged 12 to 17 have suffered at least one major depressive episode over the last 12 months. That’s more than three million children, mostly girls. Girls are almost three times as likely to suffer depressive episodes, the report said.
The trend is worrisome, experts say, especially since only 50% of depressed teens are diagnosed before adulthood and suicide is on the rise. A study last year found that the numbers of children and teens with suicidal thoughts who went to emergency rooms in the US doubled between 2007 and 2015.
The National Institute of Mental Health is currently funding three separate research projects to study the depressed teenage brain and evaluate treatments.