Challenges to Behavioral Health and Injury Surveillance During the COVID-19 Pandemic—Reply

In Reply Schoenbaum and Colpe identify important limitations to our study¹ on trends in emergency department (ED) visits for mental health, overdose, and violence before and during the COVID-19 pandemic. Specifically, they highlight 3 aspects of the data from the National Syndromic Surveillance Program (NSSP) at the US Centers for Disease Control and Prevention (CDC) that affected the interpretation of reported trends, including the expanded coverage of the NSSP over time, that analyses were not limited to EDs with consistent participation, and that rates per population were not reported.

NSSP coverage expanded from 62.4% of ED visits in the US in 2019 to 70.7% in 2020. While this growth can affect interpretability of trends, particularly following substantial declines in the overall number of ED visits, NSSP’s expansion has resulted in additional resources that have improved data quality and system functionality, including recent advances in the ability to limit analyses to facilities with consistently high discharge diagnosis code completeness and consistent reporting over time. Recently, NSSP used this methodology to characterize the effect of COVID-19 on ED visits from December 2018 to January 2021 and found results consistent with our study,¹ with more individuals seeking emergency care for mental or behavioral health and socioeconomic (eg, threats of job loss) and psychosocial concerns during the pandemic period compared with the prepandemic period.² Therefore, NSSP’s growth actually reflects a system strength, as it facilitates subset analyses that can confirm and bolster confidence in national-level study results.

While calculating rates per population is challenging because of varying NSSP coverage by state, robust population-based estimates can be determined on finer geographic scales by limiting analyses to counties with participating facilities. County-level analyses historically required state permission, but this requirement has been lifted for COVID-19 response activities to improve understanding of the effect of the pandemic on the US health care system. Recent initiatives—including the CDC’s Drug Overdose Surveillance and Epidemiology,³ Emergency Department Surveillance of Nonfatal Suicide Related Outcomes,⁴ and Firearm Injury Surveillance Through Emergency departments⁵—provide funding for state and territorial health departments to share local data with the CDC for routine monitoring of overdose, violence, and injury outcomes. These initiatives require recipients to collect at least 75% of state-level ED visits and encourage recipients to onboard new facilities, thus increasing NSSP coverage and improving opportunities to calculate rates per population at granular levels.

All data sources have strengths and limitations that affect their ability to address epidemiologic questions. Current time lags for mortality and survey data using rigorous sampling methods limit our understanding of the immediate challenges that communities face. NSSP data uniquely offer near real-time insights into nationwide ED visit trends. While the pandemic has raised awareness of existing public health data system limitations, it has also greatly increased the visibility and highlighted the value of timely syndromic surveillance data to inform public health activities. Further, novel methodologic tools within the NSSP platform enable these data to better contribute to our understanding of important public health threats over time. Future studies of ED visits for mental health, overdose, and violence will use these methods to improve interpretability of results.

Corresponding Author: Kristin M. Holland, PhD, MPH, US Centers for Disease Control and Prevention, 4770 Buford Hwy, Atlanta, GA 30341 (imh1@cdc.gov).

Published Online: June 9, 2021. doi:10.1001/jamapsychiatry.2021.1204

Conflict of Interest Disclosures: None reported.

Disclaimer: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the US Centers for Disease Control or Agency for Toxic Substances and Disease Registry.

Additional Contributions: We would like to acknowledge state, local, and jurisdictional health departments participating in the US Centers for Disease Control and Prevention National Syndromic Surveillance Program as well as the facilities working closely with these health departments to build statewide syndromic surveillance systems.