Study: Irregular Sleep Conducted to Bad Moods, Depression


Those whose waking time varies from day to day may find themselves in as much of a foul mood as those who stayed up extra late the night before, or who got up extra early that morning, according to the study authors.

An irregular sleep schedule can increase a person’s risk of depression over the long term as much as getting fewer hours of sleep overall or staying up late most nights, according to a new study.

Those whose waking time varies from day to day may find themselves in as much of a foul mood as those who stayed up extra late the night before, or who got up extra early that morning, according to the study authors.

Conducted by Michigan Medicine, the study uses data from direct measurements of the sleep and mood of more than 2100 early-career physicians over 1 year. The interns—who are first year residency training students after medical school—all experienced the long intense workdays and irregular work schedules that are the hallmark of this time in medical training. Those factors, changing from day to day, altered their ability to have regular sleep schedules.

The new paper is based on data gathered by tracking the interns’ sleep and other activity through commercial devices worn on their wrists. They were also asked to report their daily mood on a smartphone app and take quarterly tests for signs of depression.

Those whose devices showed they had variable sleep schedules were more likely to score higher on standardized depression symptom questionnaires and to have lower daily mood ratings. Further, those who regularly stayed up late or got the fewest hours of sleep also scored higher on depression symptoms and lower on daily mood. These findings add to what is already known about the association between sleep, daily mood, and long-term risk of depression.

“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,” said study author Yu Fang, MSE, in a press release. “Our findings aim not only to guide self-management on sleep habits but also to inform institutional scheduling structures.”

Cathy Goldstein, MD, MS, associate professor of neurology and physician in the Sleep Disorders Center at Michigan Medicine, noted that wearable devices that estimate sleep are now being used by millions of people, including the Fitbit devices used in the study, other activity trackers, and smart watches.

“These devices, for the first time, allow us to record sleep over extensive time periods without effort on behalf of the user,” Goldstein said. “We still have questions surrounding the accuracy of the sleep predictions consumer trackers make, though initial work suggests similar performance to clinical and research grade actigraphy devices which are cleared by the FDA.”

Additionally, Srijan Sen, MD, PhD, professor of neuroscience and psychiatry, noted that the new findings build on what his team’s work has already shown about the high risk of depression among new physicians and other underlying factors associated with a heightened risk.

“These findings highlight sleep consistency as an underappreciated factor to target in depression and wellness,” Sen said. “The work also underscores the potential of wearable devices in understanding important constructs relevant to health that we previously could not study at scale.”

Limitations of the study include the relatively young group of people evaluated and their level of degrees, being both college and medical. However, the researchers said they hope that other populations will be evaluated using similar devices and approaches to see whether the findings about variation in sleep schedule hold up for them.


Irregular sleep connected to bad moods and depression, study shows. Michigan Health Lab. Published February 18, 2021. Accessed February 18, 2021.

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