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2003 State Estimates of Substance Use

1. Introduction

This report presents State estimates for 21 measures of substance use or mental health problems based on the 2002 and 2003 National Surveys on Drug Use and Health (NSDUHs).1 Sponsored by the Substance Abuse and Mental Health Services Administration (SAMHSA), NSDUH is an ongoing survey of the civilian, noninstitutionalized population of the United States aged 12 years or older. Approximately 136,000 persons were interviewed in 2002–2003. State estimates presented in this report have been developed using a small area estimation (SAE) procedure in which State-level NSDUH 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 than estimates based solely on the survey data.

1.1. 1999–2001 NHSDA State Estimates

Beginning with the 1999 survey data, SAMHSA produced estimates at the State level for a selected set of variables (Office of Applied Studies [OAS], 2001b). 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 same measures were repeated in the questionnaire, and a modified set of questions related to substance dependence and abuse was added. These new questions capture more accurately and completely information on dependence and abuse criteria described in the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association [APA], 1994). In 2000, estimates for the 12 measures that were common to 1999 and 2000 were based on the combined data for those 2 years in order to improve their accuracy (Wright, 2002a, 2002b). In 2001, a measure for serious mental illness (SMI) was added to the questionnaire, expanding the number of measures estimated at the State level to 19. The other 18 measures were based on combined data for 2000 and 2001.

1.2. 2002 and 2003 NSDUH State Estimates

In 2002, several changes were introduced to the survey. Incentive payments of $30 were given to respondents for the first time in order to address concerns about the national and State response rates. Other changes included a change in the survey name, new data collection quality control procedures, and a shift from the 1990 decennial census to the 2000 census as a basis for population count totals and to calculate any census-related predictor variables that are used in the estimation. These changes and others improved the quality of the data provided by the survey, with the most notable result being the increase in the weighted interview response rate from 73.3 percent in 2001 (Table E.20, Wright, 2003b) to 78.6 percent in 2002 (see Table  A.1 in this report).

An unanticipated result of these changes was that the prevalence rates for 2002 were in general substantially higher than those for 2001—substantially higher than could be attributable to the usual year-to-year trend—and thus are not comparable with estimates for 2001 and prior years.2 Therefore, the 2002 NSDUH was established as a new baseline for the State, as well as national, estimates. Given the varying effects of the incentive and other changes on the States, not only are the estimates for 2002 and later years not comparable with prior years, but also the relative rankings of States may have been affected. Therefore, the rankings of States for 2002–2003 should not be compared with those for prior years.

Although the survey methodology is the same for 2002 and 2003, our investigations have demonstrated that the State-level sample sizes for the majority of States (those with annual sample sizes of approximately 900 persons) are too small to detect any trends from 1 year to the next. However, by combining data across 2 years, the precision of the small area estimates for the small States, and thus the rankings, can be significantly improved. In addition, by combining 2 years of data, the impact of the national model on those States is significantly reduced relative to estimates based on a single year's data.3 For information on the quality of the estimates, see Chapter 7 of this report. For a description of refinements made in the 2002–2003 SAE methodology relative to prior years, see Appendix A. Also included in that appendix are the State sample sizes and response rates for 2002, 2003, and 2002–2003 combined (Table s A.1 to A.6). For a more detailed discussion of the SAE methodology, see Appendix E of the 2001 State report (Wright, 2003b). Tables of model-based estimates for each substance use or mental health measure are included in Appendix B. Additional tables showing the corresponding estimated total number of persons for each measure and individual State tables listing all 21 measures are provided on the SAMHSA website (see http://www.oas.samhsa.gov/2k3State/lot.htm).

1.3. Prior NSDUH Reports on State Estimates

The Summary of Findings from the 1999 NHSDA (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, 1999 State estimates were developed for additional substance use measures for the same age groups (OAS, 2002a). In total, there were 18 measures reported. These results and all subsequent State and national estimates have been posted to the SAMHSA website (see http://www.oas.samhsa.gov/nsduh.htm and http://www.oas.samhsa.gov/states.htm).

A special State report that focused on youths (also based on the 1999 NHSDA) was released in 2001 (Wright & Davis, 2001). For the 2000 and 2001 surveys, the national results were released separately (OAS, 2001c, 2002b, 2002c) from the State results. State estimates for 2000 were released in two volumes, one with the findings and the other with technical appendices (Wright, 2002a, 2002b). National and State estimates of the drug abuse treatment gap for 2000 appeared in a separate report (OAS, 2002d). State estimates for the 2001 NHSDA also were released in two volumes, one with findings and the other with technical appendices (Wright, 2003a, 2003b). State estimates from the 2002 data were released in a single volume (Wright, 2004), separately from the 2002 national report (OAS, 2003b).

1.4. Summary of NSDUH Methodology

NSDUH 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 planned and managed by SAMHSA's OAS, and the data are collected and processed by RTI International.4 This section briefly describes the national survey methodology. 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 prisons and long-term hospitals. 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). 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 through 2001 NHSDAs and the 2002 and 2003 NSDUHs 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 accounted 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). Collectively, the sample allocated to these States ensured adequate precision at the national level while providing individual State samples large enough to support both model-based (SAE) and design-based estimates. For the remaining 42 States and the District of Columbia, smaller, but adequate, samples were selected to support State estimates using SAE techniques (described in Appendix E of the 2001 NHSDA State report, Wright, 2003b). 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, 267,000 addresses were screened and 136,000 persons were interviewed within the screened addresses. The survey is conducted from January through December each year. The screening response rate for 2002–2003 combined averaged 90.7 percent, and the interviewing response rate averaged 78.0 percent, obtaining an overall response rate of 70.7 percent. The State overall response rates for 2002–2003 ranged from 60.7 percent in New York to 82.2 percent in South Dakota (Table  A.5).

Estimates in this report have been adjusted to reflect the probability of selection, unit nonresponse, poststratification to known benchmarks, item imputation, and other aspects of the estimation process. These procedures are described in the Methodological Resource Books (MRBs) for each survey year (see

1.5. Format of Report and Presentation of Data

The findings in this report are presented in seven chapters, including this introductory chapter, along with U.S. maps at the ends of Chapters 2 through 6 and data tables in Appendix B at the end of the report.

Chapter 2 presents State estimates of the prevalence of marijuana use, incidence of marijuana use, perceived risks of marijuana use, and the prevalence of any illicit drug use, any illicit drug use other than marijuana, and cocaine use. Chapter 3 discusses analogous estimates of alcohol use, binge alcohol use, and the perceived risks of binge alcohol use. Chapter 4 presents estimates for tobacco use, cigarette use, and the perceptions of risk of heavy cigarette use. Chapter 5 discusses the substance treatment–related measures (i.e., dependence on and abuse of illicit drugs or alcohol and needing but not receiving treatment). Chapter 6 presents estimates of serious mental illness (SMI). Chapter 7 is a discussion of the findings.

At the end of Chapters 2 through 6, State model-based estimates are portrayed in U.S. maps showing all 50 States and the District of Columbia. The maps reflect the ranking of States into fifths from lowest to highest for each measure to simplify the discussion in the chapters. The quintile rankings can be determined from tables that include all 50 States and the District of Columbia, listed in alphabetical order (Appendix B), by four age categories. Appendix A gives a brief description of the SAE methodology and discusses minor refinements in that methodology for these analyses relative to prior years. Tables for individual States also are available on the SAMHSA website to display all of the estimates discussed in this report by the four age categories for a given State. Corresponding to the estimated percentages or rates for each substance use or mental health measure in Appendix B are tables of the total number of persons associated with each measure (see http://www.oas.samhsa.gov/2k3State/lot.htm).

The color of each State on the U.S. maps indicates how the State ranks relative to other States for each measure. 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 "quintile" could have more or fewer States than desired because two (or more) States have the same estimate (to two decimal places). When this occurs at the "boundary" between two "quintiles," all States with the same estimate were assigned to the lower quintile. Those States with the highest rates for a given outcome are in red, with the exception of the perceptions of risk measures, 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 measures, for which the highest perceptions of great risk are in white.

At the top of each table in Appendix B is a national total that represents the (population-weighted) mean of the estimates from the 50 States and the District of Columbia. These totals have been benchmarked in order to agree with the corresponding national estimates calculated as sample-weighted averages or proportions across the entire sample. (For more details, refer to Appendix A, Section A.4.)

Associated with each State estimate is a 95 percent prediction interval (PI). These intervals indicate the precision of the estimate. For example, the State with the highest estimated past month alcohol rate for youths aged 12 to 17 (a model-based estimate) was North Dakota, with a rate of 25.2 percent (Table  B.8). The 95 percent PI on that estimate is from 22.1 to 28.7 percent. Therefore, the probability is 0.95 that the true prevalence for North Dakota will fall between 22.1 and 28.7 percent. The PI indicates the uncertainty due to both sampling variability and model bias.

In this report, State rankings are discussed in terms of the range and the national average because the latter provide a useful context for the discussion. However, the differences between the highest (or lowest) rate and the next-to-highest (or next-to-lowest) rate are typically very small and not statistically significant. For example, although Alaska had the highest rate of past month use of an illicit drug for 2002–2003, the estimate for the District of Columbia was only 4 tenths of a percentage point lower and statistically no different than the Alaska estimate. Therefore, it is important to consider the PI when comparing States. For Alaska, one can say that 95 percent of the time the true value would fall in the range of approximately 10.3 to 14.0 percent. Clearly, the estimate for the District of Columbia falls into this range, but Utah's does not (Table  B.1).

Throughout the report, there are a number of drug measures that are related, such as marijuana use and any illicit drug use. It might appear that one could draw new conclusions by subtracting one from the other (e.g., subtracting the percentage who used marijuana in the past month from the percentage who used any illicit drug in the past month to find the percentage who used an illicit drug other than marijuana in the past month). Because related measures have not been estimated jointly, but with different models, subtracting one measure from another related measure at the State level can give misleading results, perhaps even a "negative" estimate, and should not be done.

1.6. Measures Presented in This Report

Estimates for 2002–2003 were developed for 21 measures:

1.7. Other NSDUH Reports and Products

The national results from the 2003 survey were released in September 2004 (OAS, 2004b). Additional methodological information on NSDUH, including the questionnaire, is available electronically on the OAS webpages at http://www.oas.samhsa.gov. Brief descriptive reports and in-depth analytic reports focusing on specific issues or population groups also are produced by OAS. Further information on access to NSDUH publications, detailed tables, and public use files is contained in "Accessing Data from the National Survey on Drug Use and Health (NSDUH)" (OAS, 2004a). A complete listing of previously published reports from NSDUH and other data sources is available from OAS. Most of these reports are available through the Internet (http://www.oas.samhsa.gov). In addition, OAS makes public use data files available to researchers through the Substance Abuse and Mental Health Data Archive (SAMHDA, 2004). Currently, files are available from the 1979 to 2003 surveys at http://www.icpsr.umich.edu/SAMHDA/index.html.

Early in 2005, estimates for substate planning areas based on combined 1999–2001 NHSDA data will be available at the SAMHSA website. The substate planning area definitions are currently being collected from all 50 States and the District of Columbia, using the areas for substate allocation of funds under SAMHSA's treatment block grant program. This will be the first time that substate data for the entire United States have been collected and estimated using comparable methods. Estimates will be available for each State and the District of Columbia for 12 measures related to substance use for the population aged 12 or older. Along with the substate estimates will be comparable State and regional estimates summarized in tables and maps that indicate the distribution of prevalence rates across the United States. The methodology used for producing substate estimates will be similar to the SAE methodology used to produce the State estimates in this report.


End Notes

1In 2002, the name of the survey was changed from the National Household Survey on Drug Abuse (NHSDA) to NSDUH.

2For a thorough discussion of the impact of these changes, see OAS (2003a) and Appendix C of OAS (2003b).

3Combining data across 2 years permits the estimation of change at the State level by expressing it as the difference of two consecutive 2–year SAE moving averages. Once the 2004 data are available for analysis, two estimates at the State level will be developed, one based on combined 2003–2004 data and the other on combined 2002–2003 data. This method is similar to the one used in the 2001 State report (Wright, 2003b).

4RTI International is a trade name of Research Triangle Institute.

5For details on how the average annual rate of first use of marijuana (incidence of marijuana) is calculated, refer to Section A.6 of Appendix A.

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This page was last updated on June 03, 2008.