Why Some People Are Natural Night Owls, According to Sleep Experts

If you’ve ever wondered why it’s harder for you to fall asleep at a typical bedtime or wake up early in the morning, the answer can most likely be found in your biology. Your circadian rhythm, or internal body clock, largely influences your natural sleep-wake preferences, known as chronotypes.

While biology plays a major role in determining when you feel tired and alert, your habits and environment also influence your sleep patterns and quality. According to our experts, evening light exposure, a lack of regular exercise, and an inconsistent sleep schedule can all affect when you feel ready for bed and when you naturally wake up. Even with lifestyle adjustments, however, night owls often find it more difficult to rise early than their early-bird counterparts. To better understand why some people are naturally inclined to stay up later, we asked sleep experts to explain the science behind being a night owl.

The Science Behind Being a Night Owl

Your chronotype largely determines whether you’re a night owl or a morning person, also known as a late or early type. Jennifer Martin, a professor at Florida International University’s College of Medicine, explains that chronotypes are driven by the circadian rhythm—the body’s internal clock that regulates sleep, alertness, and other essential daily functions. Genetics largely determine whether you’re a late or early type, which is why being a night owl often runs in families.

According to Kenneth Wright, a professor and director of the Sleep and Chronobiology Laboratory in the Department of Integrative Physiology at the University of Colorado Boulder, people whose internal clocks run slightly longer than 24 hours tend to stay up later and wake up later, making them more likely to be night owls. Conversely, people whose internal clocks run slightly shorter than 24 hours tend to feel sleepy earlier and wake up earlier, giving them morning-person tendencies, he says.

How a Night Owl’s Body Clock Works

Late types often wake up while their melatonin levels are still elevated, meaning their circadian clock is still promoting sleep, says Jamie Zeitzer, a professor at the Department of Psychiatry and Behavioral Sciences at Stanford University. As a result, night owls are more likely to feel sleepy upon waking. They also tend to experience greater social jet lag, sleeping later on weekends to catch up on rest, which can shift their circadian rhythm even later by Monday morning, Wright adds.

To help the body wake up, cortisol levels rise in anticipation of wake time. “This rise in cortisol helps free up energy that is important for increasing your cardiovascular tone,” Wright says. “Many night owls will wake up earlier than their circadian system is expecting, causing them to have insufficient energy when they wake up.” As a result, many night owls feel groggy in the morning because their bodies have not yet fully prepared for wakefulness.

How Habits and Environment Affect Night Owls

Certain daily habits and environmental factors can either reinforce or shift a person’s natural chronotype. For night owls, keeping lights on late into the evening, following an inconsistent sleep schedule, and not exercising regularly can make it harder to get enough sleep, Martin says.

Staying up late watching TV or scrolling through social media can further promote wakefulness, making it even more difficult to wind down at night, according to research.¹ While these habits can negatively affect both night owls and morning people, they may reinforce a night owl’s tendency to stay up late by further delaying the body’s internal clock.