Population-based surveys use different measures of mental illness. Some are administered by trained mental health professionals, and others by trained lay professionals. Some of the measures yield a psychiatric diagnosis, while others screen for the presence of symptoms or diagnostic criteria. Read on to learn about the mental illness diagnostic and screening tools used in major population-based health surveys. 

Mental Illness Diagnostic Tools

The Structured Clinical Interview for DSM Disorders (SCID)
The Research Version is considered to be the standard among psychiatric research instruments based on DSM-IV-TR criteria; the SCID takes 30-60 minutes and must be conducted by a trained mental health professional. (First, M.B. et al. (2002). Structured Clinical Interview for DSM-IV-TR axis I disorders, Research version. New York, NY: Biometrics Research, New York State Psychiatric Institute.) 

The Composite International Diagnostic Interview (CIDI)
​This measure was developed by WHO and is based on DSM-III criteria. CIDI also is intended for use in epidemiological, clinical, and research studies. CIDI takes 45-60 minutes but may be administered by trained lay interviewers. (Kessler, R.C. et al. (2004). The World Mental Health (WMH) Survey Initiative Version of the World Health Organization (WHO) Composite International Diagnostic Interview (CIDI). Int J Methods Psychiatr Res, 13, 93–121.)

The World Mental Health Composite International Diagnostic Interview (WMH-CIDI)
​This measure was developed by WHO and is based on ICD-10 and DSM-IV criteria. CIDI also is intended for use in epidemiological, clinical, and research studies. CIDI takes 45-60 minutes but may be administered by trained lay interviewers. (Kessler, R.C. et al. (2004). The World Mental Health (WMH) Survey Initiative Version of the World Health Organization (WHO) Composite International Diagnostic Interview (CIDI). Int J Methods Psychiatr Res, 4(13), 93–121.)

Mental Illness Screening Instruments

The Center for Epidemiologic Studies Depression Scale (CES-D).
This measure includes twenty items comprising six scales reflecting major facets of depression: depressed mood, feelings of guilt and worthlessness, feelings of helplessness and hopelessness, psychomotor retardation, loss of appetite, and sleep disturbance. Scores of >=16 are considered probable cases of depression. In the 11-item CESD-R, scores of >=9 are the threshold. (Radloff, L.S. (1977) ‘The CES-D scale: A self-report depression scale for research in the general population’. Applied Psychological Measurement 1: 385-401.). 
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The Patient Health Questionnaire-9 (PHQ-9)  
This measure screens for the presence of the nine DSM-IV-TR criteria for acute and clinically significant depressive disorders. 

The Patient Health Questionnaire (PHQ-8)
​This questionnaire omits the PHQ-9 question concerning suicidal or self-injurious ideation. (Reeves, W.C. et al. (2011). Mental illness surveillance among adults in the United States. MMWR Surveill Summ, 60(Suppl 3), 1-29.)

The Patient Health Questionnaire (PHQ-2) 
​These two items specifically screen for depression symptoms. (Kroenke, K. et al. (2003). The Patient Health Questionnaire-2: Validity of a two-item depression screener. Medical Care, 41, 1284-1294.) 

The Kessler-6 Psychological Distress Scale (K-6)
This measure screens for psychological distress experienced by persons with anxiety and mood disorders. Serious psychological distress as defined by the Kessler-6 score is highly associated with anxiety disorders and depression but does not identify a specific mental illness. A cut point on 13+ on the K6 is the optimal cut point for assessing the prevalence of SMI in the national population. (Andrews, G. et al. (2001). Interpreting scores on the Kessler psychological distress scale (K10). Aust N Z J Public Health, 25, 494–497.)

Health Related Quality of Life Core Module (HRQOL-4)
This module asks respondents about self-rated general health, physical health, mental health, and activity limitations resulting from poor physical or mental health during the previous 30 days. (Moriarty, D.G. et al. (2003). The Centers for Disease Control and Prevention’s healthy days measures—population tracking of per­ceived physical and mental health over time. Health Qual Life Outcomes, 2(1), 37.)

Health Related Quality of Life Mentally Healthy Days (HRQOL-MHD)
This measure asks the number of mentally unhealthy days out of the past 30 experienced by a person. Respondents who report ≥14 mentally unhealthy days over the past month are defined as having frequent mental distress. (Moriarty, D.G. et al. (2003). The Centers for Disease Control and Prevention’s healthy days measures—population tracking of per­ceived physical and mental health over time. Health Qual Life Outcomes, 2(1), 37.)

Disability Screening Assessment

The World Health Organization Disability Assessment Schedule (WHO-DAS)
​This schedule assesses functional limitations in cognition, mobility, self-care, social interactions, life activities, and community participation.    

Disability assessment in large-scale or population-based surveys
In large-scale surveys, disability can be measured either as a functional limitation or as participation in a disability benefit program (e.g., public Social Security Disability Insurance or Supplemental Security Income, or private disability insurance). As a result of the 2010 Affordable Care Act, the Department of Health and Human Services (HHS) established a standard set of six questions that assess functional disability in major government surveys. According to the HHS Implementation Guidance on Data Collection Standards for Race, Ethnicity, Sex, Primary Language and Disability Status (10/31/2011),  “The six-item set of questions used in the American Community Survey (ACS) and other major surveys to gauge disability is the data standard for survey questions on disability. This set of six disability questions represents a minimum standard, and the questions and answer categories should not be changed. Additional questions on disability may be added to any survey as long as these six questions are included.  If the ACS changes the disability questions in the future, the U. S. Department of Health and Human Services will revisit the standard and adjust the survey questions as necessary.”

The Six Disability Questions (Yes/No Responses) are:
  1. Are you deaf, or do you have serious difficulty hearing?
  2. Are you blind, or do you have serious difficulty seeing, even when wearing glasses?
  3. Because of a physical, mental, or emotional condition, do you have serious difficulty concentrating, remembering, or making decisions? (5 years old or older)
  4. Do you have serious difficulty walking or climbing stairs? (5 years old or older)
  5. Do you have difficulty dressing or bathing? (5 years old or older)
  6. Because of a physical, mental, or emotional condition, do you have difficulty doing errands alone such as visiting a doctor's office or shopping? (15 years old or older)
​See the CDC page that list population surveys that include the standard disability questions.