Potential antidote for teen depression: keep moving

A prospective study has shown a link between light physical activity and a reduction in depressive symptoms in adolescents, suggesting that switching from couch-potato mode to walking even at a casual pace might help in keeping depressive symptoms at bay.

As depression appears to start during adolescence, this may be the ideal period to implement strategies to curb depression at a later stage. [Lancet 2014;383:1404–1411; Lancet 2012;379:1056-1067] Evidence shows that physical activity may help reduce depressive symptoms; however, most have focused on moderate-to-vigorous activities (eg, brisk walking, jogging, cycling). [Neurosci Biobehav Rev 2019;107:525-539]

Light activity (eg, slow walking, standing classes), which requires less effort and is easier to integrate into a daily routine, may be more sustainable, noted the researchers. However, light activity is progressively displaced by sedentary behaviour (ie, screen time, lying/sitting still) throughout adolescence, as evidenced by the current findings.

From 12 to 16 years, time spent doing light activity decreased (mean, from 326 to 245 min/day; p<0.0001) as the duration of sedentary behaviour increased (mean, from 431 to 523 min/day; p<0.0001). [Lancet Psychiatry 2020;7:262-271]

A 60-minute/day exposure to sedentary behaviour between 12 and 16 years led to depression rates ranging from 8–11 percent at 18 years, with the strongest association observed at 12 years (incidence rate ratio, 1.11; p<0.0001). Correspondingly, every 60-minute/day light activity during the same timepoints led to a drop in depression rates by 8–11 percent.

These results reflect the consistent association between increased sedentary behaviour throughout adolescence and depressive symptoms at 18 years, said the researchers. “[These imply] that a 2-hour reduction in daily sedentary behaviour between … 12 and 16 years was associated with a 16–22-percent reduction in depression scores by 18 years. For young people with subclinical depressive symptoms, a reduction of this magnitude can have a substantial impact.”

These were observed following evaluation of a subsample of adolescents (n=4,257; 56 percent female) from the ALSPAC* study who had a CIS-R** depression score at 18 years. The amounts of time spent in sedentary behaviour and physical activity were measured using accelerometers at 12, 14, and 16 years. Participants were followed for 6 years.

Drop the remote

Evidence shows that mentally active sedentary behaviours (eg, working at a desk) may also lower the risk of depressive symptoms than mentally passive sedentary behaviours (eg, watching TV). [Br J Psychiatry 2019;1-7] Nonetheless, the study findings highlight the importance of light movement to mitigate the potential dangers of globally rising sedentary behaviour in young people, underscored the researchers.

Therefore, public health guidelines and interventional approaches should include measurable and achievable targets for promoting light activity to displace sedentary behaviour and potentially pull the adolescent depression curve down, they said. “[I]ndividual, school, or community levels [should] incorporate extended bouts of light activity into the daily routines of young people, such as standing lessons, increasing active travel time between classes, or promoting lightly active hobbies such as playing an instrument and painting.”

However, the researchers noted that attrition over time could have resulted in selection bias. There may have also been some degree of inaccuracy with accelerometer use (eg, inability to record posture), they added. Nonetheless, the long follow up period, large patient sample, and repeated objective measures fortified the groundwork for the robust findings.

“[Overall,] emphasizing the mental health benefits of physical activity would send a stronger and more relatable message given the rising prevalence of depression in adolescents,” said the researchers. Future studies should also explore the impact of physical activity and sedentary behaviour on other mental health issues such as anxiety disorders.