Summary: Staying up late is linked to worse mental health regardless of whether someone is naturally a morning or evening person. In a large study of nearly 74,000 adults, researchers found that both “morning larks” and “night owls” who habitually go to bed late show higher rates of mental and behavioral disorders. The benefit of earlier sleep applied across chronotypes, and the authors suggest aiming for sleep before 1 a.m. to support mental health.
Key Facts:
- Late bedtimes are associated with increased rates of mental and behavioral disorders, independent of chronotype.
- Both morning and evening chronotypes tend to experience better mental-health outcomes when they sleep earlier.
- The study’s practical recommendation is to go to bed before 1 a.m. to reduce mental-health risks.
Source: Stanford
Night owls, take note. A large study led by researchers at Stanford Medicine examined how a person’s preferred sleep schedule (chronotype) and their actual sleep timing relate to mental health. The surprising conclusion: staying up late appears harmful regardless of whether a person feels naturally inclined to be active at night.
The research team compared self-reported chronotype with objectively measured sleep behavior using wrist-worn accelerometers worn for seven days. Mental-health outcomes came from medical records, and diagnoses were classified using standard international codes for mental, behavioral, and neurodevelopmental disorders.
Published in Psychiatry Research, the study recommends that people aim to sleep before 1 a.m. to support better mental health.
“We found that alignment with your chronotype is not the key factor here; being up late is what correlates with poorer mental health,” said Jamie Zeitzer, Ph.D., professor of psychiatry and behavioral sciences and the study’s senior author. “The main question remaining is why this pattern exists.”
Renske Lok, Ph.D., a postdoctoral scholar in psychiatry and behavioral health, is the study’s lead author.
How did the study measure sleep and mental health?
The team analyzed data from 73,888 community-dwelling adults in the UK Biobank, focusing on middle-aged and older participants. Individuals reported whether they consider themselves morning types, evening types, or intermediate. Researchers then used accelerometer data to determine actual sleep timing over a seven-day period.
Instead of using fixed clock times, the researchers classified sleep timing relative to the cohort: the earliest 25% of sleepers were labeled “early,” the latest 25% “late,” and the middle 50% “intermediate.” This relative categorization accounts for population differences in typical bedtime norms.
Mental-health diagnoses were identified from health records using International Classification of Diseases (ICD) codes and included a broad range of mental, behavioral, and neurodevelopmental disorders, as well as depression and anxiety.
Late nights matter more than alignment
Contrary to the team’s expectations—based on prior research suggesting benefits from living in line with one’s chronotype—the data showed a consistent link between late sleep behavior and higher rates of mental-health disorders across chronotypes. In other words, being a night owl who stays up late was associated with worse outcomes than a night owl who kept earlier hours.
Specifically, night owls who maintained late sleep schedules were 20% to 40% more likely to have a recorded mental-health diagnosis than night owls who adopted early or intermediate sleep schedules. Morning types who shifted to later sleep times experienced an increased risk too, though the effect was less pronounced than for late-sleeping evening types. Overall, morning types who rose early showed the best mental-health profiles.
The researchers also examined whether shorter sleep duration or inconsistent sleep timing explained the association; these factors did not account for the observed differences. To address reverse causation—whether poor mental health causes late sleep rather than the reverse—the team followed a subset of participants without prior mental-health diagnoses for up to eight years. Those who were night owls and slept late were most likely to develop new mental-health disorders during follow-up.
Possible explanations: behavior, biology, and social context
Several hypotheses could explain why late-night behavior relates to poorer mental health. One idea is behavioral: late-night hours are associated with increased risk-taking and harmful activities (alcohol or drug use, overeating, violent behavior, and suicidal ideation), and those behaviors may contribute to worse mental-health outcomes.
Another possibility, sometimes called the “mind after midnight” hypothesis, proposes that physiological and neurological changes after midnight—such as impaired judgment and greater impulsivity—make it easier to make poor decisions at night. Morning people who stay up late may recognize their diminished capacity and be more cautious; evening people, by contrast, may feel alert and make riskier choices late at night.
Social context may also play a role. In cultures or settings where nightlife is limited and most people sleep earlier, staying up late can create social isolation and fewer supportive interactions. Conversely, in more social nighttime cultures, late hours might carry different mental-health implications.
While shifting sleep earlier can be difficult—chronotype appears to be biologically anchored—practical steps such as morning light exposure and consistent daily routines may help people move their sleep timing earlier. Zeitzer cautions that chronotype itself doesn’t change easily: it behaves like a stretched rubber band that returns toward its natural position after a lapse.
The research team plans to investigate whether specific late-night behaviors, rather than timing alone, drive the relationship with mental health. As Zeitzer put it, “If someone simply does the same low-risk activities they would normally do at 10 p.m., but at 2 a.m., that might not be harmful. The concern is more about what people do during those late hours.”
About this mental health and chronotype research news
Author: Nina Bai
Source: Stanford
Contact: Nina Bai – Stanford
Image: The image is credited to Neuroscience News
Original Research: Open access.
Title: Perils of the nighttime: Impact of behavioral timing and preference on mental health in 73,888 community-dwelling adults by Renske Lok et al., published in Psychiatry Research.
Abstract
Perils of the nighttime: Impact of behavioral timing and preference on mental health in 73,888 community-dwelling adults
Mental health is influenced both by a person’s chronotype (their preferred timing for sleep) and by their actual sleep timing, and these two factors are frequently out of sync. This study assessed how chronotype, actual sleep timing, and the alignment between them relate to mental and behavioral disorders.
Using data from 73,888 middle-aged and older adults in the UK Biobank, the investigators combined questionnaire-based chronotype information with seven-day accelerometry to classify actual sleep behavior. Mental-health outcomes (mental, behavioral, and neurodevelopmental disorders, depression, and anxiety) were identified using ICD-10 diagnostic codes from health records.
Compared with morning types who slept early (aligned), morning types who slept late (misaligned) had higher risks of mental, behavioral, and neurodevelopmental disorders, depression, and anxiety (p’s < 0.001). In contrast, evening types who adopted an earlier sleep schedule (misaligned) showed a lower risk of depression (p < 0.01) and trends toward lower risk for other disorder categories.
Longitudinal analyses that tracked the onset of new mental-health diagnoses supported the cross-sectional findings: late sleep timing predicted greater likelihood of developing mental-health disorders over time.
The takeaway recommendation from the study is practical: to support healthy aging and mental well-being, individuals should aim to go to sleep before 1 a.m., regardless of their chronobiological preference.