Mental illnesses are common in the United States, with the 2021 National Survey on Drug Use and Health (NSDUH) by the Substance Abuse and Mental Health Services Administration (SAMHSA) estimating that they affected over 20% of U.S. adults or 57.8 million. Moreover, the survey estimated that 14.1 million household-dwelling adults aged 18 or older live with serious mental illness (e.g., schizophrenia, bipolar disorder, major depressive disorder), which substantially interferes with or limits one or more major life activities. Mental illness, particularly serious mental illness (SMI), is thus a significant public health problem. Yet surveillance systems have traditionally left several gaps in the understanding of these issues among people who do not reside in households, e.g., homeless, institutionalized, or incarcerated populations, who have disproportionately high rates of mental and substance use disorders.

To address this gap, the Mental and Substance Use Disorders Prevalence Study (MDPS) was launched in 2019 as a SAMHSA-funded cooperative agreement with RTI International. Between October 2020 and October 2022, this study conducted 5,679 clinical interviews among 18–65-year-olds, including those living in households, prisons, state psychiatric hospitals, and homeless shelters. Key findings related to prevalence and treatment rates include:

  • One in four adults lived with at least one mental disorder in the past year, with major depressive disorder (15.5%) and generalized anxiety disorder (10.0%) being the most common;
  • Almost 3.7 million individuals (1.8%) have a lifetime diagnosis of a schizophrenia spectrum disorder, a rate much higher than previously estimated; and
  • Six in ten adults with a mental disorder received treatment at least once in the past year.

There may be differences in findings from MDPS and NSDUH, due to the many differences in the methodologies used by the two studies. In particular, NSDUH restricts the study to persons living in households and homeless shelters. Other major differences between MDPS and NSDUH include the age of respondents: 18-65 vs 12 and older; the sampling methods used: probability- and nonprobability-based vs strictly probability-based; the sample size: 5,679 vs 69,850; the nature of the interview and interviewers: clinical vs self-report and clinician vs nonclinical field interviewer; the interview administration mode: virtually or in-person by the clinician vs self-administrated; data collection duration: 2 years vs annually; the mental disorders outcomes: specific SMIs vs three general categories; and treatment outcomes of interest. These differences complicate a direct comparison of the findings from the two studies.

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