Remember when you were a teenager and the weekends were your chance to catch up on all that sleep you missed during the week? If you were a normal teenager at a normal school, you probably missed sleep during the week because of all the fun social activities you had and the fact that school started too early in the morning. If you were a nerd like me, at a nerd school, it was because you had about 5 hours of homework a night and a calculus teacher that insisted your calculus homework should only take half an hour because that’s how long it took her to do it. I digress.
It turns out that a major imbalance in sleep between weekdays and weekends for adolescents is not a good thing at all. This shift in sleep is something researchers call “social jet lag”. A paper from the labs of Ron Dahl and Erika Forbes was just released in Biological Psychology with results from a study showing that brain structures of adolescents with this kind of sleep imbalance just don’t respond as much to monetary rewards as adolescents with a more consistent sleep pattern across the week. They found that this lack of response had more to do with the shift in sleeping time rather than the total number of hours slept – in other words, it wasn’t just sleep deprivation that was associated with the change in brain function.
Why do we care if teenagers’ brains don’t respond to reward? It’s associated with a lot of bad outcomes, including increased risk-taking behaviours, substance abuse, and even mood disorders like depression. Previous studies have shown that social jet lag in adolescents has been linked to these sorts of behaviours, but this study is the first to show a neural basis for the association.
However, this study only looked at the kids at one point in time, so the authors do point out that we can’t be sure if the sleep problems were causing the lack of brain response, or if the lack of response to reward meant that adolescents were looking for bigger “thrills” by staying up late on the weekends. We need more longitudinal research to answer these kinds of questions, i.e., studies that follow up kids over a number of years.
These guys consistently put out top-quality research informing our knowledge of adolescent development so it’s great to see some work by them supporting the importance of sleep hygiene (i.e., good sleeping habits) in this age (although I should disclose a conflict of interest in that my lab is currently collaborating on a sleep intervention trial with Ron Dahl).
You can read the abstract for this study here