Figure 1. Monthly Percentage of Male and Female Adolescents Aged 13 to 18 Years With Mental Health Diagnoses of Anxiety or Depression Between January 2018 and March 2022.

The β-coefficients with corresponding 95% CIs in parentheses represent the change in level and slope in percentage of adolescents with the respective mental health conditions. Solid lines represent the observed trends. Dashed lines represent the estimated linear trends in the respective period. The vertical lines divide the assessment period into 3 periods: the prepandemic period (January 2018 to March 2020), the early period of the pandemic when school closure was common (April 2020 to September 2020), and the recent period of the pandemic after schools started to reopen (October 2020 to March 2022). Different y-axis scales were chosen to account for variations in prevalence across mental health diagnostic groups. The monthly proportion of 13- to 18-year-old male and female adolescents with mental health diagnoses was assessed according to the presence of at least 1 outpatient or inpatient mental health diagnosis of interest among all youths enrolled in the respective month.