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2000 State Estimates of Substance Use & Mental Health

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1. Introduction

This report presents State estimates for 17 measures related to substance use based on the 1999 and 2000 National Household Surveys on Drug Abuse (NHSDAs). Since 1971, the NHSDA has been an ongoing survey of the civilian, noninstitutionalized population of the United States aged 12 years old or older. State estimates presented in this report and related prior releases are based on a small area estimation (SAE) procedure in which State-level NHSDA data are combined with local-area county and Census block group/tract-level data from the State. These model-based estimates provide more precise estimates of substance use at the State level.

Beginning in 1999, the NHSDA produced estimates at the State level for a selected set of variables. These variables included prevalence rates for a number of licit and illicit substances, perceptions of risks of substance use, and other measures related to substance dependence and abuse. In 2000, 12 of the measures were repeated in the NHSDA questionnaire, and a modified set of the questions related to substance dependence and abuse was substituted. These new questions more accurately and completely captured information on dependence and abuse used in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association [APA], 1994).

For the new (modified) measures related to substance dependence and abuse, State estimates used only the data from the 2000 NHSDA. For the 12 measures that were identical in 1999 and 2000, estimates were based on combined 1999 and 2000 data. Because year-to-year changes at the State level were relatively small, and the relative variance of the changes was large, the decision was made to combine the 1999 and 2000 NHSDA data for improved estimates of the 12 measures common to both years. For details on the SAE methodology, including discussion of the survey-weighted hierarchical Bayes estimation approach, evaluation of change estimates, and methodology used to produce the 2-year averages, see Appendix B in Volume II.

1.1 Prior Releases of State Estimates

The Summary of Findings from the 1999 NHSDA (Office of Applied Studies [OAS], 2000) presented national estimates of substance use and, for the first time, State estimates for seven priority variables for all persons aged 12 or older and three age groups (12 to 17, 18 to 25, and 26 or older):

Subsequently, State estimates for additional substance use measures were developed for those aged 12 or older, 12 to 17, 18 to 25, and 26 or older. Those measures were as follows:

The estimates produced included both an estimate for each State and the 95 percent prediction interval (PI). Together, the 18 measures represent the complete set of State model-based estimates calculated for 1999.

Subsequent to the publication of the Summary of Findings from the 1999 NHSDA (OAS, 2000), an error was discovered in the imputation procedure that significantly affected some of the national and State prevalence estimates. This error was corrected for the 1999 estimates in this report, the 1999 estimates on the OAS website (OAS, 2002a), and the 1999 estimates in a State youth report (Wright & Davis, 2001). (See Appendix E in Volume II for a fuller discussion.)

1.2 Summary of NHSDA and State Methodology

The NHSDA is the primary source of statistical information on the use of illicit drugs by the U.S. civilian population aged 12 or older. 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, under the direction of SAMHSA's OAS. This section briefly describes the NHSDA methodology. A more complete description is provided in Appendix D in Volume II.

The survey covers 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. Appendix F in Volume II describes surveys that include populations that are not part of the NHSDA sampling frame.

Prior to 1999, the NHSDA was administered in about an hour and used paper-and-pencil interviewing (PAPI) methods. 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 interviewers was not aware of respondent answers. Less sensitive questions, such as demographics, occupational status, household size, and composition, were asked aloud by the interviewer and recorded in the questionnaire booklet.

The 1999 NHSDA marked the first survey year in which the national sample was interviewed using a computer-assisted interviewing (CAI) method. The survey used 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 an interviewer are still administered by an interviewer, but CAPI is used. Questions previously administered using answer sheets are now administered using ACASI. CAI has many advantages over PAPI, including more efficient collection and processing of the data and improved data quality. Use of ACASI is designed to provide the respondent with a highly private and confidential means of responding to questions and should increase the level of honest reporting of illicit drug use and other sensitive behaviors. For further details on the development of the CAI procedures for the 1999 NHSDA, see OAS (2001a).

The 1999 and 2000 NHSDAs 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 design-based 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 (described in Appendix B in Volume II). The design also oversampled youths and young adults, so that each State's sample was approximately equally distributed among three major age groups: 12 to 17 years, 18 to 25 years, and 26 years or older.

Nationally, addresses were screened and persons were interviewed within the screened addresses. The 1999 survey was conducted from January through December 1999, and the 2000 survey in the analogous period in 2000. The screening response rates for 1999 and 2000 were 89.6 percent and 92.8 percent, respectively. The interview rate was 68.6 percent in 1999 and 73.9 percent in 2000. The overall response rates for 1999 and 2000 were 61.4 percent and 68.6 percent, respectively. Weighted overall response rates for 1999 for individual States ranged from 49.8 to 78.2 percent. The range in 2000 was somewhat better-from 58.2 to 80.6 percent. For more detail, see Table s B.27 and B.28 in Appendix B in Volume II.

Estimates in this report have been adjusted to reflect the probability of selection, record nonresponse, poststratification to known benchmarks, item imputation, and other aspects of the estimation process.

1.3 Format of Report and Presentation of Data

The findings presented in this report are divided into five main chapters in Volume I, along with U.S. maps at the ends of chapters and data tables in Appendix A at the end of this volume. Five supplementary technical appendices are provided in a separately bound Volume II.

Chapter 2 presents 1999 and 2000 State estimates of marijuana use, incidence of marijuana use, perceived risks of marijuana use, any illicit drug use, any illicit drug use except marijuana, and cocaine use. Chapter 3 discusses estimates of alcohol use, "binge" alcohol use, and the perceived risks of "binge" alcohol use. Chapter 4 focuses on estimates of tobacco use, cigarette use, and the perceptions of risks of heavy cigarette use. Chapter 5 discusses the substance treatment-related measures (i.e., dependence on and abuse of illicit drugs or alcohol). Chapter 6 is a discussion of the findings.

At the ends of Chapters 2 to 5, State model-based estimates are portrayed in U.S. maps showing all 50 States and the District of Columbia. These estimates also are provided in tables that include all 50 States and the District of Columbia by four age categories (Appendix A) and in individual State tables arranged to display all of the estimates discussed in this report by the four age categories for a given State (Appendix C in Volume II). The color of each State on the U.S. maps indicates how the State ranks relative to other States for each indicator. States could fall into one of five groups according to their ranking by quintiles. Because there are 51 areas to be ranked, the middle quintile was assigned 11 areas and the remaining groups 10 each. In some cases, a group may have contained more or fewer areas than this number because the estimates were the same as for other States in the group. Those States with the highest rates for a given variable are in red, with the exception of the perceptions of risk variables, for which the lowest perceptions of great risk are in red. Those States with the lowest estimates are in white, with the exception of the perceptions of risk variables, for which the highest perceptions of great risk are in white. For the model-based estimates, when two or more States fell on the border between adjoining quintiles and had identical estimates to two decimal places, those States were assigned to the lower quintile.

At the top of each table in Appendix A is a "national" total that represents the (weighted) sum of the estimates from the 50 States and the District of Columbia. Those totals are generally slightly different from the corresponding national estimates calculated by summing the sample-weighted records across the entire sample. The latter estimates are the preferred unbiased estimates for the Nation and are used in the text for comparison with the State-level estimates.

Associated with each State estimate is a 95 percent PI. These intervals indicate the precision of the estimate. For example, the State with the highest estimated past month alcohol rate for youths (a model-based estimate) was North Dakota, with a rate of 26.2 percent (Table A.14). The 95 percent PI on that estimate is from 23.1 to 29.5 percent. Therefore, the probability is 0.95 that the true prevalence for North Dakota will fall between 23.1 and 29.5 percent. The PI indicates the uncertainty due to both sampling variability and model bias.

1.4 Measures of Substance Use Presented in This Report

Estimates based on combined 1999-2000 NHSDA data were developed using 12 measures:

Other estimates based on 2000 NHSDA data were collected using five measures:

The NHSDA includes questions on a number of factors associated with a higher likelihood (risk factors) or lower likelihood (protective factors) of substance use. Among these, low perceptions of risk of substance use are often associated with higher levels of substance use (see Wright & Davis, 2001; Wright & Pemberton, in press). In this report, State-level estimates of the perceptions of risk of marijuana use, "binge" alcohol use, and cigarette use are presented.

1.5 Calculation of Average Annual Incidence of Marijuana Use

Incidence rates are typically calculated as the number of new initiates of a substance during a period of time (such as in the past year) divided by the estimate of the number of person years of exposure (in thousands). The incidence measure in this report is the result of a simpler definition but is based on the model-based methodology mentioned earlier in this chapter and discussed further in Appendix E in Volume II. The definition in this report is as follows:

Average annual incidence rate = 0.5 * {Number of initiates in past 24 months /
[(Number of initiates in past 24 months * 0.5) + Number of persons who never used]}.

Note that this estimate uses a 2-year time period to accumulate incidence cases from each annual survey. By assuming further that the distribution of first use for the incidence cases is uniform across the 2-year interval, the total number of person years of exposure is 1 year on average for the incidence cases plus 2 years for all the never users at the end of the time period. This approximation to the person years of exposure permits one to recast the incidence rate as a function of two population prevalence rates, namely, the fraction of persons who first used marijuana in the past 2 years and the fraction who had never used marijuana. Both of these prevalence estimates were estimated using the survey-weighted hierarchical Bayes estimation approach.

The count of persons who first used marijuana in the past 2 years is based on a "moving" 2-year period that ranges over 3 calendar years. Subjects were asked when they first used marijuana. If a person indicated first use of marijuana between the day of the interview and 2 years prior, the person was included in the count. Thus, it is possible for a person interviewed in the first part of 1999 to indicate first use as early as the first part of 1997 or as late as the first part of 1999. Similarly, a subject interviewed in the last part of 1999 could indicate first use as early as the last part of 1997 or as late as the last part of 1999. Therefore, in the 1999 survey, the reported period of first use ranged from early 1997 to late 1999 and was "centered" in 1998. About half of the 12 to 17 year olds who reported first use in the past 24 months reported first use in 1998, while a quarter each reported first use in 1997 and 1999. Persons who responded in 1999 that they had never used marijuana were included in the count of "never used." Reports of first use in the past 24 months from the 2000 survey ranged from early 1998 to late 2000 and were centered in 1999. For the 12 to 17 year olds, about half of these reports of first use from the 2000 survey occurred in 1999 and one quarter each occurred in 1998 and 2000. For further information on the general procedures for calculating incidence rates, see Appendix E in Volume II.

1.6 Other NHSDA Reports and Products

In August 2000, the first report of the 1999 NHSDA data was released-the Summary of Findings from the 1999 NHSDA (OAS, 2000). In addition to national results, that report included estimates for the 50 States and the District of Columbia for seven model-based variables by four age groups (ages 12 or older, ages 12 to 17, ages 18 to 25, and ages 26 or older). Additional tabulations have been generated from the 1999 data and are available at the OAS website (OAS, 2002a). Further methodological information will be posted to the website as it becomes available. Analytic reports focusing on specific issues or population groups will continue to be produced by OAS. A few of the reports in progress or recently published focus on the following topics:

A complete listing of previously published reports from the NHSDA and other data sources is available from OAS, and many of these reports are also available through the Internet (see Acknowledgments on page ii). In addition, OAS makes public use data files available to researchers through the Substance Abuse and Mental Health Data Archive (SAMHDA, 2002). Currently, files are available from the 1979 through the 1999 NHSDAs.

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This page was last updated on December 30, 2008.