Importance In the general population, depression increased with the onset of the COVID-19 pandemic. In addition to the general pandemic impact, training physicians faced many sudden and dramatic changes in their training environment. However, the effects of these changes on the mental health of training physicians remains unknown.

Objective To identify change in depression risk among training physicians with the onset of the COVID-19 pandemic and factors associated with risk.

Design Prospective cohort study.

Setting University- and community-based health care institutions in the United States and Shanghai, China

Participants First-year resident physicians (interns) serving during the 2018-19 (n=1844), 2019-20 (n=1201), and 2020-21 (n=2448) academic years (U.S. sample); interns serving during the 2021-22 academic year (n=471) (Shanghai sample)

Main Outcomes and Measurements Depressive symptoms (Patient Health Questionnaire-9 [PHQ-9]) and work hours were assessed quarterly for all U.S. cohorts. The 2019-20 cohort completed supplemental surveys of these measures in April and May 2020. Shanghai sample interns were assessed for depressive symptoms (PHQ-9) and work hours quarterly before, during, and after the 2022 lockdown.

Results Within the 2019-20 U.S. cohort, depressive symptom scores decreased from the pre-pandemic (September, December) to the pandemic period (April, May, June) (5.5 [3.9] vs. 4.9 [4.3], p<0.001). In causal mediation analysis, 62% of this change was mediated through work hours (0.62, 95% CI [0.44-1.00]). Descriptive comparisons of this cohort with cohorts training immediately before (2018-19) and after (2020-21) the pandemic onset demonstrated that both work hours and depressive symptoms were significantly lower in spring 2020, but returned to pre-pandemic levels by fall 2020. In the parallel Shanghai cohort serving during the April 2022 lockdown, we found a similar magnitude drop in depressive symptoms (5.6 [3.3] vs. 4.9 [4.8], p=0.005), with 64% of the effect mediated through work hours (0.64, 95% CI [0.24-1.84]).

Conclusions and Relevance Interns experienced a 11% decrease in depressive symptoms with the onset of the pandemic, which was primarily driven by reduced work hours. The identified associations between work hours and depressive symptoms early in the pandemic may inform strategies to support physician wellness moving forward.

Question How did depressive symptoms in training physicians change during the COVID-19 pandemic?

Findings In a prospective cohort study including 1201 U.S. first-year residents during the 2019-2020 academic year, we found an 11% decrease in depressive symptoms with the pandemic onset. Causal mediation analysis identified that work hours mediated 62% of this change. These findings were replicated in a parallel cohort of 471 Shanghai residents, where work hours mediated 64% of the 11% decrease in depressive symptoms during the 2022 lockdown.

Meaning The identified decreases in depressive symptoms mediated through work hours can inform future reforms to support resident well-being.

The authors have declared no competing interest.

Funding/Support: National Institute of Mental Health (R01 MH101459) to Dr. Srijan Sen and T32 fellowship 5T32HL110952-09 to Dr. Pereira-Lima); An investigator grant from Precision Health Initiative at University of Michigan, Ann Arbor (to Drs. Zhenke Wu and Srijan Sen). ​​Shanghai Education Commission Research and Innovation Program (2019-01-07-00-02-E00037), Program of Shanghai Subject Chief Scientist (17XD1401700), the 111 Program of Higher Education Discipline Innovation, Shanghai Jiao Tong University Scientific and Technological Innovation Funds (to Dr. Weidong Li).

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study design was approved by the Institutional Review Board at the University of Michigan and the participating hospitals in the Intern Health Study (HUM00033029).

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I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

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I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

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Data underlying the present analysis are available upon request to the authors, and data from the Intern Health Study are available from ICPSR.