Prevalence of Any Mental Illness Among Adults in the US

"The 2020 NSDUH provided estimates of any mental illness (AMI) and serious mental illness (SMI) for adults aged 18 or older. Adults aged 18 or older were classified as having AMI if they had any mental, behavioral, or emotional disorder in the past year of sufficient duration to meet DSM-IV criteria (excluding developmental disorders and SUDs).^18,79

"Adults who were classified as having AMI were classified as having SMI if they had any mental, behavioral, or emotional disorder that substantially interfered with or limited one or more major life activities. Statistical prediction models that were developed using clinical interview data from a subset of NSDUH adult respondents in 2008 to 2012 were used to classify whether respondents in the 2008 to 2020 adult samples had AMI or SMI in the past year.⁸⁰

"As noted previously, a set of break-off analysis weights was developed for adults’ mental health data for 2020. Estimates of AMI and SMI for 2020 used these break-off analysis weights.

"Among adults aged 18 or older in 2020, 21.0 percent (or 52.9 million people) had AMI in the past year (Table A.29B). The percentage was highest among young adults aged 18 to 25 (30.6 percent or 10.2 million people), followed by adults aged 26 to 49 (25.3 percent or 25.7 million people), then by adults aged 50 or older (14.5 percent or 16.9 million people).

"Serious Mental Illness among Adults in the Past Year

"Among adults aged 18 or older in 2020, 5.6 percent (or 14.2 million people) had SMI in the past year (Figure 32). Consistent with the age group pattern for AMI, the percentage of adults with SMI was highest among young adults aged 18 to 25 (9.7 percent or 3.3 million people), followed by adults aged 26 to 49 (6.9 percent or 7.0 million people), then by adults aged 50 or older (3.4 percent or 4.0 million people)."