teen boy asleep in grass with backpack nearbyTeens are notorious for sleeping in late, staying up late and always feeling tired. They seem very different from their younger selves. Younger children hop out of bed near dawn and usually drift off to sleep by 8PM. Parents and researchers have long noticed this change in sleep style and assumed it was due to external factors, such as social activities, homework and TV or computer use. It isn’t only that. In the 1990s scientists found out the shift in sleep patterns has a large biological component stemming from changes in the way melatonin works. However, genes and behavior are also involved.

Melatonin is a hormone that governs a person’s circadian rhythms, including the sleep-wake cycle. This cycle influences both how long we sleep and when we sleep. During puberty there is a change in melatonin secretion so that it occurs later in the cycle. As a result, at least 2/3 of teens truly don’t get tired at 9 or 10 PM. In fact, they’re often quite alert at that time. This is different from children, who tire after dinner, and also from adults, who begin unwinding by 8PM and typically become sleepy around 10 PM. In contrast, teens may not tire until midnight, or even later! However, teens still need a good amount of sleep: about 9 ¼ hours. (Children need about 10 hours and adults about 8 ¼ hours.)

Other biological factors are also involved in sleep. There are genetic influences. Some people truly are “morning people,” while others feel more alert later in the day. This tends to run in families, though certainly not everyone in a family will have the same pattern. We cannot change this tendency, it’s part of who we are.

Light also has a role. It interacts with and influences circadian rhythms. Bright morning light helps trigger a feeling of waking up, just as darkness influences a feeling of sleepiness.

In addition to biology, teens may get less sleep than they need because of their lifestyle choices. It is easy to loose track of time when doing homework, using social media, texting, playing computer games, researching things on the internet and so on. Everyone with a computer knows this. Teens have always had a call to be socially engaged (a few decades ago it was by telephone) and in today’s world they have many ways to stay connected to friends through the various social networking options.

teen girl upside down on her bedOne reason teens feel so sleepy is because their sleep cycle is at odds with their usual daily schedule. Because school starts early, teens typically have to get up between 6 AM and 7AM. This means they are getting just 4 to 7 hours of sleep — far less than they need. As a result, many teens truly are sleep deprived.

Part 2 of this article Provides strategies for helping your teen manage sleep needs