Sleep study finds night owl habit may be detrimental to mental health

Owls should get ready. A new study from Stanford Medicine researchers found that following your natural tendency to stay up until the early hours of the morning has negative effects on your mental health.

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

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

"We found that matching your chronotype is not a deciding factor, and in fact, staying up late at night is not good for your mental health," said Jamie Seitzer, Ph.D., 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 lead author of the study.

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

“There’s a lot of data that suggests living in alignment with your chronotype is really important,” he said. “That was our expectation.”

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

The 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 relative to 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 consistent with your chronotype wasn't the best choice for mental health. In fact, it was better for night owls to live a life that was out of chronotype.

"I thought, 'Let's try to disprove this, because it doesn't make sense,'" Zeitzer recalled. "We spent six months trying to disprove it, and we 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 health disorder than night owls who followed an early or intermediate sleep schedule.

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

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

The researchers found that sleep duration and consistency of sleep time 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 subgroup of participants who had no previous diagnosis of a mental disorder over the next eight years. During this time, night owls who went to bed late were more likely to develop mental disorders.

Or is it about the elections? There may be many explanations for the link between sleep timing and mental well-being, but Seitzer believes it most likely has to do with poor decisions people make in the early morning hours.

Many harmful behaviors are more likely to occur at night, including suicidal ideation, violent crime, alcohol and drug use, and overeating.

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

This may explain why, even late at night, morning types seem to have an advantage - they are 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 as well as they should, so they can put off making bad decisions," Seitzer said.

"Meanwhile, the evening person, staying up late at night, thinks: 'I feel great. This is a great decision for me to make at three o'clock in the morning.'"

Another explanation could be social incongruity with the underlying chronotype.

"There may be fewer social restrictions late at night because there are fewer people around you who are awake," Seitzer said. This is especially true in places like the US and UK, where people tend to be more isolated in the evenings. In Mediterranean culture, where nights are more sociable, staying awake may even be beneficial for mental health.

Although Seitzer advises night owls to go to bed before 1 a.m., he knows that's easier said than done. Getting sunlight in the morning and keeping an earlier schedule each day of the week may change your sleep habits, but it doesn't change your chronotype. "From a biological perspective, 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 itself, are associated with poor mental health.

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