Getting seven or eight hours is not enough, study finds.
Sleeping irregular hours increases the risk of depression, even if the total amount of sleep is sufficient, research finds.
People who sleep and wake at different times are just as likely to suffer depression as those who do not get enough sleep overall.
The findings highlight how important it is to maintain regular hours of sleep — on top of getting enough total sleep.
Irregular sleep schedules may cause mental health problems by disrupting circadian rhythms, the researchers suggest.
Circadian rhythms are the natural sleep-wake cycles of the body.
Sleep may be more restorative when it coincides with melatonin production and lower core body temperature, which are two circadian rhythms which help the body prepare for sleep.
For the study, researchers tracked over 2,100 young doctors as they battled through their first year of training after completing medical school.
Trainee doctors are well-known to experience highly irregular work schedules, along with reduced time for sleep.
Psychologists gathered information about their sleep and wake patterns through wearable devices.
Ms Yu Fang, the study’s first author, said:
“The advanced wearable technology allows us to study the behavioral and physiological factors of mental health, including sleep, at a much larger scale and more accurately than before, opening up an exciting field for us to explore.
Our findings aim not only to guide self-management on sleep habits but also to inform institutional scheduling structures.”
The results showed that trainee doctors with the most variable sleep schedules scored the highest on depression tests — they also had the worst moment-to-moment mood.
Professor Srijan Sen, study co-author, said:
“These findings highlight sleep consistency as an underappreciated factor to target in depression and wellness.
The work also underscores the potential of wearable devices in understanding important constructs relevant to health that we previously could not study at scale.”
Parents of young children will be well aware of the damaging effects of irregular sleep schedules on mental health.
Ms Fang joked:
“I also wish my 1-year-old could learn about these findings and only wake me up at 8:21 a.m. every day.”
The study was published in the journal npj Digital Medicine (Fang et al., 2021).
