Longer work weeks increase depression risk in first-year physicians

Working more than 90 hours per week was associated with higher levels of depression in first-year physicians, a recent study found.

“The proportion of physicians who have a positive screening for depression increases by a factor of five to six times with the start of residency,” Yu Fang, MSE, a research area specialist lead at the University of Michigan Molecular and Behavioral Neuroscience Institute, and colleagues wrote in a correspondence in The New England Journal of Medicine. “The long work hours that are typical of residency are a potential driver of worsening depressive symptoms.”

Fang and colleagues analyzed data on 17,082 physicians who, from 2009 to 2020, were recruited into the Intern Health Study, a sampling of physicians in their first postgraduate year.

The participants completed a nine-item version of the Patient Health Questionnaire (PHQ-9) 1 to 2 months before the start of the internship and then quarterly throughout the internship.

“On the PHQ-9, depression is categorized as minimal by a score of 0 to 4, mild by a score of 5 to 9, moderate by a score of 10 to 14, moderately severe by a score of 15 to 19 and severe by a score of 20 to 27,” the researchers wrote.

At baseline, participants’ median PHQ-9 score was 2 points, while the median number of hours worked per week was 67.

Fang and colleagues reported that participants who had higher work-level hours also had total PHQ-9 scores indicating greater levels of depression, “with 33.4% of the interns meeting PHQ-9 criteria for depression at a level of more than 90 work hours per week.”

In work-hour categories of more than 40 and up to 45 hours per week, the PHQ-9 score increased an estimated 1.8 points (95% CI, 1.7-2) from baseline. That increase was 5.2 points (95% CI, 4.9-5.6) in work weeks of more than 90 hours.

The researchers acknowledged that because it was an observational study, the results could be contributed to residual confounding, though methods and approaches emulated a clinical trial.

Speaking to Healio, study coauthor Amy S.B. Bohnert, PhD, MHS, an associate professor in the department of psychiatry at the University of Michigan, noted that it was a surprise to see how much of a dose-response effect was present, instead of a threshold effect.

“It suggests that it is important to try to continue to reduce work hours overall, not just to avoid the most extreme schedules,” she said.

Bohnert added that one of the potential factors increasing the harm of long work hours may be the effect on sleep, “especially because overnight shifts are often a contributor to high sleep hours.”

“It is important to better understand these relationships and the degree to which this is a mechanism,” she said.

References:

• Fang Y, et al. N Engl J Med. 2022;doi:10.1056/NEJMc2210365.
• In stressful jobs, depression risk rises with hours worked, study in new doctors finds. https://www.eurekalert.org/news-releases/968159. Published Oct. 19, 2022. Accessed Oct. 25, 2022.