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New Report Provides National Clinical Data on the Prevalence of Many Specific Mental Disorders

Science Update

This week the Substance Abuse and Mental Health Services Administration (SAMHSA) released the findings of a new clinical study providing national data on the prevalence of specific mental disorders in adults. The CBHSQ Data Review: Past Year Mental Disorders among Adults in the United States presents data from the Mental Health Surveillance Study (MHSS) on the past-year prevalence of mood disorders, anxiety disorders, eating disorders, substance use disorders, adjustment disorder, and psychotic symptoms.

As part of a $5 million American Recovery and Reinvestment Act (ARRA) investment from NIMH, SAMHSA took advantage of a unique opportunity to collect clinician-assessed diagnostic information from a representative sample of the US population. In the MHSS, researchers applied follow-up clinical assessments to a subset of existing data that had been collected as part of SAMHSA’s annual National Survey on Drug Use and Health (NSDUH).

The NSDUH—one of the primary sources of mental health indicators in the US—uses a computer-assisted self-administered questionnaire to gather information about the prevalence of major depressive episode and other mental-health related symptoms and associated impairments. While the NSDUH methodology allows SAMHSA statisticians to generate model-based estimates of the prevalence of serious mental illness (SMI) in the nation, this model-based statistical approach does not generate annual percentages of adults with specific mental disorders, such as generalized anxiety disorder, dysthymic disorder, or other specific mental disorders.

Clinical interviews, such as those used in the MHSS study, can be used to fine-tune and/or validate self-report or lay-administered mental disorder assessment questionnaires, such as those used in the NSDUH study. Clinical interviews themselves are rarely feasible in epidemiological studies because of the considerable effort and expense it takes to train, hire, and supervise a cadre of clinicians to field a comprehensive study in a large nationally representative sample.

For this effort, SAMHSA expanded the MHSS clinical calibration project. They increased the originally planned number of follow-up clinical assessments collected from a subset of NSDUH participants from 3,500 to over 5,500.

The instrument used in the MHSS was the Structured Clinical Interview for DSM-IV-TR Axis I Disorders (SCID-I)— widely considered a “gold standard” for structured clinical psychiatric assessment. In the MHSS, the SCID-I was used to screen participants for past-year (and in a few cases, lifetime) experience with 16 different mental disorders. A further detailed clinical assessment was administered to all respondents who screened positive for any of these disorders. Interviews were conducted by trained clinical interviewers over the telephone and subsequently reviewed by doctoral-level clinical supervisors.

The benefits of expanding the clinical sample size were two-fold. First, by the end of 2012, SAMHSA researchers collected over 5,500 clinical interviews from which they were able to calculate reliable estimates of the prevalence of specific mental disorders among US adults in the prior 12 months. Second, having 2,000 additional respondents in the MHSS allowed SAMHSA to generate much more precise estimates of SMI overall.

Additional information about the MHSS is now publicly available on the SAMHSA website.