Irregular Sleeping Patterns Linked to Depression, Bad Mood in First-Year Medical Students

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Irregular sleeping patterns can increase a person’s risk of depression and lower their daily mood over the long term as much as getting fewer hours of sleep or staying up late most nights, according to a new study of first-year medical students.

Published February 18, 2021 in npj Digital Medicine, researchers from Michigan Medicine—the University of Michigan’s academic medical center—examined the sleeping habits of interns during their first year of physician training, which is known for its long intense work days and irregular work schedules.

Researchers gathered data on the interns’ sleep and other activity through wearable devices on their wrists; asked them to track daily mood on a smartphone app; and, administered the 9-item Patient Health Questionnaire (PHQ-9) quarterly to test depression symptoms.

Using the Intern Health Study, a multisite prospective cohort study that has been tracking mood and depression risk of first-year medical residents for >10 years, researchers picked 2115 participants to be included in the current study.

The Intern Health Study collected an average of 2 weeks of data from before the physicians’ intern years started, and an average of 4 months of monitoring through their intern year.

Interns whose wearable devices showed they had irregular sleeping schedules and those who regularly stayed up late or got the fewest hours of sleep, were more likely to score higher on the PHQ-9 and to have lower daily mood ratings, according to the study.

Even next day mood was worsened by reduced sleep duration, later bedtime, earlier wake time, and larger shifts in total sleep time and wake time.

“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 lead author Yu Fang, MSE, research specialist, Michigan Neuroscience Institute, in a university press release. “Our findings aim not only to guide self-management on sleep habits but also to inform institutional scheduling structures.”

Researchers did note that the relatively young age of participants (mean age, 27 years) and their high academic levels are not representative of the general population; however, they were a good group to test hypotheses in because they had similar workloads and schedules.

Future research should examine other populations using similar devices and approaches to find out if these current findings hold true for them, according to study authors.