Trends in the Incidence of New-Onset Anorexia Nervosa and Atypical Anorexia Nervosa Among Youth During the COVID-19 Pandemic in Canada

IMPORTANCE: The COVID-19 pandemic has had considerable mental health consequences for children and adolescents, including the exacerbation of previously diagnosed eating disorders. Whether the pandemic is a factor associated with the concomitant increase in new-onset anorexia nervosa or atypical anorexia nervosa remains unknown. OBJECTIVE: To assess the incidence and severity of newly diagnosed anorexia nervosa or atypical anorexia nervosa in a national sample of youth before and during the first wave of the COVID-19 pandemic. DESIGN, SETTING, AND PARTICIPANTS: This repeated cross-sectional study analyzed new eating disorder assessments that were conducted at 6 pediatric tertiary-care hospitals in Canada between January 1, 2015, and November 30, 2020. Patients aged 9 to 18 years with a new anorexia nervosa or atypical anorexia nervosa diagnosis at the index assessment were included. EXPOSURES: COVID-19–associated public health confinement measures during the first wave of the pandemic (March 1 to November 30, 2020). MAIN OUTCOMES AND MEASURES: Primary outcomes were the incidence and hospitalization rates within 7 days of de novo anorexia nervosa or atypical anorexia nervosa diagnosis. Event rate trends during the first wave were compared with trends in the 5-year prepandemic period (January 1, 2015, to February 28, 2020) using an interrupted time series with linear regression models. Demographic and clinical variables were compared using a χ(2) test for categorical data and t tests for continuous data. RESULTS: Overall, 1883 children and adolescents with newly diagnosed anorexia nervosa or atypical anorexia nervosa (median [IQR] age, 15.9 [13.8-16.9] years; 1713 female patients [91.0%]) were included. Prepandemic anorexia nervosa or atypical anorexia nervosa diagnoses were stable over time (mean [SD], 24.5 [1.6] cases per month; β coefficient, 0.043; P = .33). New diagnoses increased during the first wave of the pandemic to a mean (SD) of 40.6 (20.1) cases per month with a steep upward trend (β coefficient, 5.97; P < .001). Similarly, hospitalizations for newly diagnosed patients increased from a mean (SD) of 7.5 (2.8) to 20.0 (9.8) cases per month, with a significant increase in linear trend (β coefficient, −0.008 vs 3.23; P < .001). These trends were more pronounced in Canadian provinces with higher rates of COVID-19 infections. Markers of disease severity were worse among patients who were diagnosed during the first wave rather than before the pandemic, including more rapid progression (mean [SD], 7.0 [4.2] months vs 9.8 [7.4] months; P < .001), greater mean (SD) weight loss (19.2% [9.4%] vs 17.5% [9.6%]; P = .01), and more profound bradycardia (mean [SD] heart rate, 57 [15.8] beats per minute vs 63 [15.9] beats per minute; P < .001). CONCLUSIONS AND RELEVANCE: This cross-sectional study found a higher number of new diagnoses of and hospitalizations for anorexia nervosa or atypical anorexia nervosa in children and adolescents during the first wave of the COVID-19 pandemic in Canada. Research is needed to better understand the drivers and prognosis for these patients and to prepare for their mental health needs in the event of future pandemics or prolonged social isolation.