Dear Grace,

Hang on tight because the human brain keeps you on a 24-hour roller coaster.

Every day the human body produces a chemical messenger in the brain called melatonin. It tells the body when it is time to go to bed.

“It’s just like your parents,” said my friend Samantha Gizerian, an assistant professor at Washington State University, who studies how kid and baby brains develop. “Except you can’t run away from melatonin.”

Melatonin goes up at night, peaks while you are sleeping, and comes down in the morning. Melatonin levels stay low across the afternoon and start to rise again in the evening. Your brain also cools down as you fall asleep, warms up during the day, and then cools off again before bedtime.

Gizerian said you can’t run away from melatonin because it works with the sun. As it gets darker outside, the nerves in your eyes perceive less light. That’s how the brain knows to start producing melatonin. This also why it’s important to turn off any screens or lights before bed—otherwise your brain might think it is daytime and you won’t sleep well. You’ll be feeling like a zombie the next day.

“You are always going to be more alert in the mid-morning or afternoon, whether you are an early bird or a night owl,” Gizerian said, causing my ears to perk up at the talk of both birds and sleep.

She also explained that most of what scientists know about young brains actually comes from studying older, teenage brains. Babies and kids like to move around a lot and much of the research requires the study subject to stay still.

Scientists know teenage brain clocks are about two hours behind those of full-grown adults, so when adult brains are hard at work, young brains are still warming up. Their bodies are also producing other kinds of messengers that are helping them grow.

“That delay may be a way that the brain has developed for more rest and recovery,” Gizerian said, “but who knows.”

So, to answer your question, young brains do not work better in the morning. Some studies have shown students even perform better on tests when they take them in the afternoon, Gizerian said. In fact, almost all the research on teenage brains shows they function better in the afternoon. A good night’s sleep helps, too.

I could attest to this from my personal experience and will celebrate Brain Awareness Week and National Nap Day this month with a lot of catnaps.

Years ago sleep researchers wondered why teenagers liked to stay up so late, preferred to sleep-in, and were so sleepy in the morning, Once they found out about melatonin patterns in their brains, researchers wondered why this chemical rollercoaster was going on at all. It’s a question that still puzzles them.


Dr. Universe