Going to bed late, regardless of whether you’re a night owl or an early bird by nature, is linked to worse mental health, according to a new study by Stanford University researchers.
Scientists had believed that aligning your sleep behavior to your sleep time preference — “evening people” going to sleep later, and “morning people” going to sleep earlier — was beneficial for mental health. This is known as aligning to your chronotype.
But the latest study suggests, to researchers’ surprise, that going to bed late is potentially harmful for the mental health of all individuals, regardless of their natural sleep time preferences, as it’s linked to higher rates of depression and anxiety.
“We found that alignment with your chronotype is not crucial here, and that really it’s being up late that is not good for your mental health,” said the study’s senior author Jamie Zeitzer, a Stanford professor of psychiatry and behavioral sciences. “The big unknown is why.”
Both morning people and evening people who went to sleep late had higher rates of depression and anxiety, according to the study, which was published this month in Psychiatry Research.
Night owls who went to sleep late were the most negatively impacted: They were 20%-40% more likely to have been diagnosed with a mental health disorder than night owls who went to sleep on an early or intermediate schedule.
Early birds who went to sleep late also suffered in terms of their mental health, but not as much as the night owls.
Early birds who went to bed early, and awoke with the sun, fared the best.
The findings were determined independent of sleep duration and consistency of sleep timing.
For healthy aging, the study recommends that people go to bed before 1 a.m., regardless of whether they identify as night owls or early birds.
“It’s important to get to sleep before 1 a.m.,” Zeitzer said. “That’s the one-sentence takeaway.”
The analysis included about 74,000 middle-aged and older adults in the United Kingdom. Researchers tracked their sleep using a wearable activity tracker for seven days, and noted from their health records any diagnoses of mental or behavioral disorders. About a quarter of the participants self-identified as evening people; 9% considered themselves morning people; 65% were somewhere in the middle.
The study did not attach a specific bedtime to be considered “early” or “late,” but rather grouped the participants in three categories, relative to each other’s sleep time — 25% were early sleepers, 25% were late sleepers, and 50% were intermediate or middle sleepers. The 1 a.m. cutoff was based on the distribution of participants’ sleep times.
The study did not attempt to answer why mental health appears linked to sleep timing. But researchers think it could be related to actions and behaviors that people tend to take or experience in the very early morning hours, such as alcohol and drug use, overeating and suicidal thoughts. People also tend to be more isolated late at night, with fewer people around who are also awake, and thus fewer social guardrails.
Zeitzer is now taking the study a step further and examining whether certain behaviors that people engage in late at night are associated with positive or negative mental health outcomes.
“If you’re up late binge-watching Netflix, does that have the same outcome as if you were up late because you’re hanging out with friends?” he said. “If you’re staying up late, does it matter what you’re doing? That’s the next step.”