Sleep study finds that habit of being an 'owl' can be detrimental to mental health

Night owls, brace yourself. A new study from Stanford Medicine has found that following your natural inclination to stay up until the early hours of the morning can have negative effects on your mental health.

In a survey of nearly 75,000 adults, researchers compared participants’ preferred sleep times, known as chronotypes, with their actual sleep behavior. They found that regardless of their preferred bedtime, everyone is better off going to bed earlier. Morning larks and night owls are equally likely to suffer from mental and behavioral problems if they stay up late.

A study published in the journal Psychiatry Research recommends turning off lights before 1 a.m.

"We found that being in your chronotype wasn't the deciding factor, and in fact, staying up late at night wasn't good for your mental health," said Jamie Zeitzer, PhD, professor of psychiatry and behavioral sciences and senior author of the study. "The big question is why."

Renske Locke, PhD, a postdoctoral fellow in psychiatry and behavioral health, is the study's lead author.

How do you sleep at night? The results weren't quite what the researchers expected. Previous research by Zeitzer's team suggested that women with cancer who slept contrary to their chronotype had shorter life expectancies.

"There's a lot of data that suggests that living within your chronotype is very important," he said. "That was our expectation."

The researchers decided to study chronotype compliance in a larger population. They studied middle-aged and older adults in the U.K. who were asked about their sleep patterns, including their preference for mornings or evenings. They were sent wearable accelerometers (essentially sophisticated activity monitors, Seitzer said) to track their sleep for seven days.

Participants' mental health was determined from their medical records. The researchers included any mental or behavioral disorders listed in the International Classification of Diseases.

Among the 73,880 participants, 19,065 identified themselves as morning types, 6,844 as evening types, and 47,979 as middle types.

Their sleep behavior was assessed for the entire group. The earliest 25 percent were considered early sleepers, the latest 25 percent were considered late sleepers, and the middle 50 percent were considered in between. Categorizing sleep behavior this way, rather than by specific time frames, makes more sense because different populations may have different sleep norms, Zeitzer said. "If we were doing this study in college students, 1 a.m. obviously wouldn't be considered late."

It's All About Timing When the researchers analyzed the data, they were surprised to find that being in chronotype alignment was not the best choice for mental health. In fact, it was better for night owls to live out of chronotype alignment.

"I thought, 'Let's try to disprove this because it doesn't make sense,'" Seitzer recalled. "We spent six months trying to disprove it and couldn't."

The results were clear - both morning and evening types who went to bed late had higher rates of mental health disorders, including depression and anxiety.

"The worst-case scenario is people who stay up late at night," Zeitzer said. Night owls who stuck to their chronotype were 20 to 40 percent more likely to be diagnosed with a mental disorder than night owls who followed an early or intermediate sleep schedule.

Evening types who followed an earlier schedule felt better. Morning types who went to bed later suffered, but not much.

Larks who rose with the sun had the best mental health of all, which surprised no one.

The researchers found that sleep duration and sleep time consistency could not explain these differences in mental health.

They also tested the possibility that it was poor mental health that was causing people to stay up late, rather than the other way around. They tracked a subset of participants who had no previous diagnosis of a mental disorder for the next eight years. During that time, the night owls who stayed up late were more likely to develop mental disorders.

Or is it about choices? There could be many explanations for the connection between sleep time and mental well-being, but Zeitzer thinks it's more likely to be about the bad decisions people make in the early morning hours.

Many harmful behaviors occur more frequently at night, including suicidal thoughts, violent crime, alcohol and drug use, and binge eating.

One theory, known as the "mind after midnight" hypothesis, suggests that neurological and physiological changes late at night may contribute to impulsivity, negative mood, poor judgment, and greater risk-taking.

This may explain why even late at night, morning types seem to have an advantage - they're out of their comfort zone. "If I had to guess, morning people who stay up late at night are aware that their brains aren't working the way they should, so they may put off making bad decisions," Zeitzer said.

"Meanwhile, the evening person, who stays up late at night, thinks, 'I feel great. This is a great decision I'm making at three o'clock in the morning.'"

Another explanation may be social mismatch with the underlying chronotype.

"There may be fewer social constraints late at night because there are fewer people around you who are awake," Zeitzer said. This is especially true in places like the U.S. and U.K., where people tend to be more isolated in the evenings. In Mediterranean cultures, where nights are more sociable, staying awake may even be good for mental health.

While Zeitzer advises night owls to go to bed before 1 a.m., he realizes that's easier said than done. Getting sunlight in the morning and sticking to an earlier schedule every day of the week may change your sleep habits, but it doesn't change your chronotype. "From a biological standpoint, it's a lot like a rubber band — you take a day off and you get back to where your body wants to be," he said.

His team plans to study whether certain nighttime behaviors, rather than the time of day itself, are linked to poor mental health.

"If you like staying up late and you're just doing what people normally do at 10 o'clock at night, but you're doing it at 2 or 3 o'clock in the morning - maybe that's not a problem," he said. But is there any joy in that?