The key findings from the NSDUH 2021 report include: - 1 in 5 adolescents had a major depressive episode in the past year, with nearly 75% experiencing severe impairment. - Nearly 1 in 4 adults aged 18 and older had a mental illness in the past year. - 61.2 million people (21.9% of the population) aged 12 or older used illicit drugs in the past year. - 9.2 million people aged 12 or older misused opioids in the past year. - 94% of people with a substance use disorder did not receive any treatment.