Just how important is sleep during the teenage years? It is well-known that newborns and toddlers need a lot of sleep to get through the day. Emerging research from our lab shows that teens are also vulnerable to the effects of poor sleep, both in their behavior and in brain development and functioning.
Text: Adriana Galván
Parents, educators, and adolescents themselves blame media and technology for increasingly poor sleep as puberty hits. Indeed, adolescents say they stay up late to juggle social demands, homework, extra-curricular activities, after-school jobs, and technology. However, what few people realize is that there are also biological reasons for this change in sleep.
At around the time pubertal hormones start to kick in, many adolescents begin to experience what is referred to as sleep-wake “phase delay,” which is a preference for later bedtime and wake times. This phase delay is typically a shift of up to 2 hours compared to children in middle childhood; whereas the average bedtime is 9:24 pm for 6th graders in the U.S., it is 11:02pm for 12th graders. Interestingly, this phenomenon is observed all around the world in individuals of all different cultures.
What does biology have to do with going to bed?
First, melatonin, the hormone that helps signal sleepiness is released in the body later in the evening in teens compared to adults. This makes falling asleep at an earlier bedtime difficult for many teenagers.
Second, teenagers experience a change in their “sleep pressure,” in which the pressure or desire to fall asleep increases more slowly than in children.
This leads to a higher tolerance for being awake. Both factors make it easier for most adolescents to stay awake later without feeling sleepy. The problem is that even though they have a higher tolerance for being awake, adolescents continue to need as much sleep as children (and no one would argue about whether or not a newborn or toddler needs a lot of sleep!). So how is the teenager supposed to get as much sleep as when they were earlier if their body is encouraging staying up later? The answer is simple. Nature intended for adolescents to go to bed later but also to wake up later yet modern society threw a wrench in these plans by imposing early school start times. As a result, many adolescents stay up late on school nights, get insufficient sleep and then struggle to stay awake in class the following day.
Is poor sleep actually harmful to teens?
In a recent study, my collaborators and I found that in addition to moodiness, there are negative effects on academic performance and brain function. We enrolled a group of teenagers into the study who told us about their daily sleep habits for two weeks. We also collected information about their mood, academic performance, stress levels and general well-being. We expected the research to show that teens who got less sleep overall would have worse outcomes on all of these dimensions but the data surprised us. Instead, we found that greater sleep variability was more harmful than chronically low sleep duration, such that teens whose sleep varied dramatically from one night to the next showed worse academic performance in school (as measured by their grade point average) and less engagement of the brain regions that help us learn new information.
This phenomenon is known as “social jet lag,” which refers to inconsistent sleep patterns. This term is usually used to describe differences in the amount of sleep a person receives between weekday and weekend nights but also reflects sleep variability on a day-to-day basis more generally. In a second analysis of the data, we considered the effects of daily stress on the link between excessive sleep variability and compromised brain function. The results show that when teenagers are performing a risky choice computer game following a very stressful day, they take more risks and show less engagement of the insula, a brain region involved in risk assessment. However, this effect was only true for those teens who had received insufficient sleep the night before they played the risky choice game, suggesting that sleep loss may amplify the effects of stress on behavior, and specifically, may make bad decisions even worse.
The good news is that sleep habits can be changed
Parents prioritize informing their teens about the dangers of many health-related risks, including promiscuous sex, reckless driving and drug use. Unfortunately, the perils of poor sleep is not one of those dangers parents warn teens about. New parents obsess over their newborn’s sleep but over time, this obsession wanes. According to a large study by the National Sleep Foundation a few years ago, only 29% of parents surveyed were aware of the mismatch between how much teens are supposed to sleep and how much they actually sleep. This points to a troubling lack of parental awareness regarding the extent of insufficient sleep in their adolescents.
The good news is that sleep habits can be changed! The emerging research on teen sleep can help empower teens, parents and educators to take control of their sleep patterns to get as much as they need. The first step is communicating the importance of sleep and supporting this message with neurobiological research in teens, just as our lab and labs around the world are working diligently to do.