A new study has found that teens who sit for too long may be damaging their mental health however, light activity can reduce the risk

Children who spend too much time sitting still also known as sedentary behaviour, are at an increased risk of developing depression by the age of 18, a new study by researchers at University College London (UCL) has found.

However, the research, which was published recently in The Lancet Psychiatry journal, also found that children who did an extra 60 minutes of light activity a day, such as walking or doing chores at the age of 12, were at a reduced risk of developing depressive symptoms by the time they reached 18.

“Our findings show that young people who are inactive for large proportions of the day throughout adolescence face a greater risk of depression by age 18. We found that it’s not just more intense forms of activity that are good for our mental health, but any degree of physical activity that can reduce the time we spend sitting down is likely to be beneficial,” said the study’s lead author, PhD student Aaron Kandola, UCL Psychiatry.

“We should be encouraging people of all ages to move more, and to sit less, as it’s good for both our physical and mental health.”

The research team used data from 4,257 adolescents, who have been participating in longitudinal research from birth as part of the University of Bristol’s Children of the 90s cohort study. The children wore accelerometers to track their movement for at least 10 hours over at least three days, at ages 12, 14 and 16.

The accelerometers reported whether the child was engaging in light activity (which could include walking or hobbies such as playing an instrument or painting), engaging in moderate-to-physical activity (such as running or cycling), or if they were sedentary.

Depressive symptoms, such as low mood, loss of pleasure and poor concentration, were measured with a clinical questionnaire. The questionnaire measures depressive symptoms and their severity on a spectrum, rather than providing a clinical diagnosis.

Between the ages of 12 and 16, total physical activity declined across the cohort, which was mainly due to a decrease in light activity (from an average of five hours, 26 minutes to four hours, five minutes) and an increase in sedentary behaviour (from an average of seven hours and 10 minutes to eight hours and 43 minutes).

The researchers found that every additional 60 minutes of sedentary behaviour per day at age 12, 14 and 16 was associated with an increase in depression score of 11.1, 8 or 10.5 per cent, respectively, by age 18. Those with consistently high amounts of time spent sedentary at all three ages had 28.2 per cent higher depression scores by age 18.

Every additional hour of light physical activity per day at age 12, 14 and 16 was associated with depression scores at age 18 that were 9.6, 7.8 and 11.1 per cent lower, respectively.

The researchers found some associations between moderate-to-vigorous activity at earlier ages and reduced depressive symptoms, although they caution that their data was weaker due to low levels of activity of such intensity in the cohort (averaging around 20 minutes per day), so the findings do not clarify whether moderate-to-vigorous activity is any less beneficial than light activity.

While the researchers cannot confirm that the activity levels caused changes to depressive symptoms, they accounted for potentially confounding factors such as socioeconomic status, parental history of mental health, and length of time wearing the accelerometer, and adjusted their analysis to account for people with depressive symptoms at the beginning of the study.

“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. The number of young people with depression also appears to be growing and our study suggests that these two trends may be linked,” Aaron Kandola added.

The study’s senior author, Dr Joseph Hayes, UCL Psychiatry and Camden and Islington NHS Foundation Trust said, “A lot of initiatives promote exercise in young people, but our findings suggest that light activity should be given more attention as well.”

“Light activity could be particularly useful because it doesn’t require much effort and it’s easy to fit into the daily routines of most young people. Schools could integrate light activity into their pupils’ days, such as with standing or active lessons. Small changes to our environments could make it easier for all of us to be a little bit less sedentary,” he added.

Commenting on the study, Ms Janis Morrissey, Head of Health Promotion, Information and Training at the Irish Heart Foundation said, “As we approach exam time, it’s good to remember that physical activity can be a supportive tool. We would encourage all young people to be as active as possible, not just through sport but by moving more throughout the day. Not only can physical activity help improve mental and physical health, but it has also been shown to improve educational attainment.”

“Given it’s pivotal role in supporting cardiovascular health, physical activity is a strategic priority for the Irish Heart Foundation, with a particular focus on children and young people. We support teachers to deliver the curriculum through inclusive and non-competitive programmes that make being active fun. Just over a year ago, we launched YPATH PE4Me which has revolutionised the way PE is taught in secondary schools. We already have an uptake of one third of schools.

“We are now focusing our energies on primary schools, working with DCU to re-develop our Action for Life programme. It will take an innovative, rounded approach including the knowledge, emotional and physical aspects of physical activity, in line with the PE and SPHE curriculum,” she added.

For more information on ways to move more during the day please see here