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National and State Estimates of Drug Abuse Treatment Gap 

Chapter 1. Description of the NHSDA

1.1 Overview

This report presents information from the 2000 National Household Survey on Drug Abuse (NHSDA) on the number and percentage of the population in the Nation and in each State who need but did not receive treatment for an illicit drug use problem, referred to as the "treatment gap."

The NHSDA is an annual survey of the civilian, noninstitutionalized population of the United States who are 12 years old or older. It is the primary source of statistical information on the use of illegal drugs by the U.S. population. Conducted by the Federal Government since 1971, the survey collects data by administering questionnaires to a representative sample of the population through face-to-face interviews at their place of residence. The survey is sponsored by the Substance Abuse and Mental Health Services Administration (SAMHSA), and data collection is carried out by RTI of Research Triangle Park, North Carolina. The project is planned and managed by SAMHSA's Office of Applied Studies (OAS). This chapter contains a summary of the survey methodology.

1.2 NHSDA Methodology

The NHSDA collects information from residents of households, noninstitutional group quarters (e.g., shelters, rooming houses, dormitories), and civilians living on military bases. Persons excluded from the survey include homeless people who do not use shelters, active military personnel, and residents of institutional group quarters, such as jails and hospitals.

Prior to 1999, the NHSDA was conducted using a paper-and-pencil interviewing (PAPI) method, with an interview lasting about an hour. The NHSDA PAPI instrumentation consisted of a questionnaire booklet completed by an interviewer and a set of individual answer sheets completed by a respondent. All substance use questions and other sensitive questions appeared on the answer sheets so that the interviewer was not aware of the respondent's answers. Less sensitive questions, such as those on demographics, employment status, and household composition, were asked aloud by the interviewer and recorded in the questionnaire booklet.

Since 1999, the NHSDA interview has been carried out using a computer-assisted interviewing (CAI) method. The survey uses a combination of computer-assisted personal interviewing (CAPI) conducted by an interviewer and audio computer-assisted self-interviewing (ACASI). For the most part, questions previously administered by the interviewer are nowadministered by the interviewer using CAPI. Questions previously administered using answer sheets are now administered using ACASI, which is designed to provide the respondent with a highly private and confidential means of responding to questions and to increase the level of honest reporting of illicit drug use and other sensitive behaviors. Nevertheless, NHSDA estimates of treatment need and the treatment gap are based on self-reports, and their accuracy depends on respondents' truthfulness and memory. Because it is assumed that there is some level of underreporting by respondents, and because heavy drug users are believed to be underrepresented in the NHSDA sample because it is household-based, estimates of treatment need and the treatment gap based on the NHSDA are considered conservative.

Consistent with the 1999 NHSDA, the 2000 NHSDA sample employed a 50-State design with an independent, multistage area probability sample for each of the 50 States and the District of Columbia. The eight States with the largest population (which together account for 48 percent of the total U.S. population aged 12 or older) were designated as large sample States (California, Florida, Illinois, Michigan, New York, Ohio, Pennsylvania, and Texas). For these States, the design provided a sample large enough to support direct State estimates. For the remaining 42 States and the District of Columbia, smaller but adequate samples were selected to support State estimates using small area estimation (SAE) techniques. The design oversampled youths and young adults, so that each State's sample was approximately equally distributed among three age groups: 12 to 17 years, 18 to 25 years, and 26 years or older. To enhance the precision of trend measurement, half of the first-stage sampling units (area segments) in the 1999 sample were also in the 2000 sample. However, all of the households included in the 2000 sample were new.

Nationally, 169,769 addresses were screened for the 2000 survey and 71,764 persons were interviewed within the screened addresses. The survey was conducted from January through December 2000. Weighted response rates for household screening and for interviewing were 92.8 and 73.9 percent, respectively.

1.3 Remainder of This Report

Chapter 2 presents national estimates of the need for treatment and the treatment gap. Overall treatment need and treatment gap estimates are discussed first, followed by discussion of treatment need estimates arranged by age, gender, race/ethnicity, geographic area, education, and employment. Chapter 3 focuses on State treatment gap estimates and includes a summary of the methodology used to calculate these estimates followed by the results and discussion. Two appendices also are included. Appendix A provides information on the measurement of dependence, abuse, treatment, and treatment need, and Appendix B provides technical details on the State estimation methodology.

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This page was last updated on June 03, 2008.