Serious Mental Illness (SMI) among Adults

  • While mental disorders are common in the United States, their burden of illness is particularly concentrated among those who experience disability due to serious mental illness (SMI).
  • The data presented here are from the National Survey on Drug Use and Health (NSDUH), which defines SMI as:
    • A mental, behavioral, or emotional disorder (excluding developmental and substance use disorders);
    • Diagnosable currently or within the past year;
    • Of sufficient duration to meet diagnostic criteria specified within the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV);
    • Resulting in serious functional impairment, which substantially interferes with or limits one or more major life activities.
  • In 2012, there were an estimated 9.6 million adults aged 18 or older in the U.S. with SMI in the past year. This represented 4.1 percent of all U.S. adults.

Prevalence of serious mental illness among U.S. adults by sex, age, and race in 2012


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Statistical Methods and Measurement Caveats

Diagnostic Assessment:

  • The NSDUH SMI estimates are generated from a prediction model that includes data from a subset of adult NSDUH respondents who completed a past 12-month version of the Structured Clinical Interview for the DSM-IV-TR Axis I Disorders (Research Version, Non-patient Edition (SCID-I/NP)).
  • The assessment included diagnostic modules assessing:  mood, anxiety, eating, impulse control, substance use, adjustment disorders, and a psychotic symptoms screen.
  • The assessment did not contain diagnostic modules assessing:  adult attention deficit hyperactivity disorder (ADHD), autism spectrum disorders, schizophrenia or other psychotic disorders (although the assessment included a psychotic symptom screen).
  • People who only have disorders that are not included in these diagnostic modules may not be adequately detected.  However, there are known patterns of high comorbidities among mental disorders;  these patterns increase the likelihood that people who meet SMI criteria were detected by the study, as they may also have one or more of the disorders assessed in the SCID-I/NP.

Population:

  • The entirety of NSDUH respondents for the SMI estimates is the civilian, non-institutionalized population aged 18 years old or older residing within the United States.
  • The survey covers residents of households (persons living in houses/townhouses, apartments, condominiums; civilians living in housing on military bases, etc.) and persons in non-institutional group quarters (e.g., shelters, rooming/boarding houses, college dormitories, migratory workers' camps, halfway houses).
  • The survey does not cover persons who, for the entire year, had no fixed address (e.g., homeless and/or transient persons not in shelters); were on active military duty; or who resided in institutional group quarters (e.g., correctional facilities, nursing homes, mental institutions, long-term hospitals).
  • Some people in these excluded categories have SMI, but they are not accounted for in the NSDUH SMI estimates.

Non-response Bias:

  • In 2012, 28% of the NSDUH adult sample did not complete the interview. 
  • Reasons for non-response to interviewing include: refusal to participate (20%); respondent unavailable (2%); physical or mental incompetence (2%); no one at home/not answering the door (1-2%); language barriers (1-2%).
  • People with SMI may disproportionately fall into these non-response categories. While NSDUH weighting includes non-response adjustments to reduce bias, these adjustments may not fully account for differential non-response by mental illness status.

Please see the 2012 SAMHSA NSDUH Mental Health Findings report for further information on how these data were collected and calculated.