Boston, MA—Reopening schools during the COVID-19 pandemic was linked with significantly lower rates of mental health diagnoses among children, including anxiety, depression, and attention-deficit/hyperactivity disorder (ADHD), and a drop in related health care spending, according to a new study from researchers at Harvard T.H. Chan School of Public Health and colleagues. The benefits were especially pronounced among girls. The study was published Monday, Dec. 8, 2025, in Epidemiology.