1. Introduction

This report presents State estimates for 19 measures of substance use or mental health problems based on the 2001 National Household Survey on Drug Abuse (NHSDA). Since 1971, the NHSDA has been an ongoing survey of the civilian, noninstitutionalized population of the United States age 12 years old or older. State estimates presented in this report are based on data collected in 1999 and later and have been developed using 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 with the 1999 NHSDA data, the Substance Abuse and Mental Health Services Administration (SAMHSA) produced estimates at the State level for a selected set of variables (Office of Applied Studies [OAS], 2002b). 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 NHSDA questionnaire, and a modified set of new questions related to substance dependence and abuse were added. These new questions more accurately and completely capture information on dependence and abuse criteria described in the 4^th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association [APA], 1994). For the 2000 report of State estimates, the 12 measures that were common to 1999 and 2000 had their estimates based on the combined data for those years in order to improve their accuracy (Wright, 2002a, 2002b).

In 2001, 18 measures shared common definitions for 2000 and 2001. Estimates of prevalence were based on the combined data for those years. One new measure, serious mental illness (SMI), was introduced in 2001.

Because 12 of the measures utilized the same definitions from 1999 through 2001, it was possible for the first time to estimate change between the prevalence rates based on combined 1999–2000 data and data combined for 2000–2001. For details on the SAE methodology, including a discussion of the survey-weighted hierarchical Bayes estimation approach, the methodology used to produce the 2-year averages and the estimates of change, and the validation results, see Appendix E in Volume II.

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 age 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 SAMHSA, and data collection is carried out by RTI of Research Triangle Park, North Carolina, under the direction of the Office of Applied Studies (OAS) in SAMHSA. This section briefly describes the NHSDA methodology. A more complete description is provided in Appendix F 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 H in Volume II describes surveys that include populations that are not part of the NHSDA sampling frame.

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 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 age 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 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 and 2001 surveys in the analogous periods in those years. The screening response rates for 1999, 2000, and 2001 were 89.6 percent, 92.8 percent, and 91.9 percent, respectively. The interview response rate was 68.6 percent in 1999, 73.9 percent in 2000, and 73.3 percent in 2001. The overall response rates for 1999, 2000, and 2001 were 61.4 percent, 68.6 percent, and 67.4 percent, respectively. 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. In 2001, State response rates ranged from 55.3 to 78.5 percent. For more details, see Table s E.18 to E.20 in Appendix E in Volume II.

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.

1.3. Format of Report and Presentation of Data

The findings presented in this report are divided into seven main chapters, including this introductory chapter, in Volume I, along with U.S. maps at the ends of Chapters 2 through 6, and data tables in Appendices A and B at the end of this volume. Six supplementary appendices are provided in a separately bound Volume II.

Chapter 2 presents State estimates of marijuana use, incidence of marijuana use, perceived risks of marijuana use, any illicit drug use, any illicit drug use other than marijuana, and cocaine use. Estimates are produced for the combined 2000–2001 period and for change between 1999–2000 and 2000–2001. 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) for the 2000–2001 period. Chapter 6 presents SMI estimates based solely on the 2001 NHSDA. Chapter 7 is a discussion of the findings.

At the ends of Chapters 2 to 6, State model-based estimates are portrayed in U.S. maps showing all 50 States and the District of Columbia. 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. Individual State tables also are provided 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 "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 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.

At the top of each table in Appendix B 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 24.7 percent (Table B.7). The 95 percent PI on that estimate is from 21.6 to 28.1 percent. Therefore, the probability is 0.95 that the true prevalence for North Dakota will fall between 21.6 and 28.1 percent. The PI indicates the uncertainty due to both sampling variability and model bias.

For the first time, estimates of change between 1999–2000 and 2000–2001 are presented (see Table s A.1 to A.12). These tables show the estimates for 1999–2000 and 2000–2001 and a p value to test the hypothesis that there was "no change" over this period. Although the usual standards of significance in NHSDA publications utilize p values of 0.01 or 0.05 (corresponding to a probability of 99 or 95 percent, respectively, that the change was not 0), p values of 0.10 have occasionally been used. The methodology for estimating change involves estimating one model for 1999–2000 based on the predictor variables and the sample for those years and a separate model for 2000–2001 based on the predictor variables and sample for those years. This can lead to slightly different national models (i.e., models with slightly different model coefficients for the two sets of years). If the models were identical for the combined years, the change between 1999–2000 and 2000–2001 would equal the average yearly change between 1999 and 2001. "Average yearly change" indicates the change between 1999 and 2001 divided by 2. Because the national models for 1999–2000 and 2000–2001 are not generally equal, and the influence of the national model relative to the 2 years of data can vary depending on the relative precision of each, the estimates of State change generally will not be equal to the average change between 1999 and 2001. However, conceptualizing it as such is probably the best way to interpret the change. For more details on this topic, see the section on validation of change in Appendix E.

The NHSDA standards for tests of significance have been extended in this analysis to include the p = 0.10 level in the analysis of change because the year-to-year changes are usually small and relatively hard to detect. As noted in Chapter 7, the significance levels quoted in Appendix A tables are somewhat conservative. A more precise significance-level calculation presented in Appendix E yielded p values that were reduced by a multiple ranging from 0.94 to 0.79. The discussion also has been extended in this report to include States that have changed the category in which they were ranked by two or more quintiles, depending on the measure (e.g., a change of a State from ranking in the top fifth in 1999–2000 to ranking in the middle fifth in 2000–2001). For some measures, such as those with low prevalence rates, the estimates reflect a good deal of variation between 1999–2000 and 2000–2001; thus, many more States have apparent changes of two or more quintiles. For such measures, the discussion has been limited to changes of three or more quintiles.

The discussion of quintile ranking is primarily descriptive and is not based on actual tests of significance. For significance, one must rely on the tests of significance that are presented in Table s A.1 to A.12. Therefore, a State may have changed its quintile rank by two or more quintiles, yet the estimate for 1999–2000 may not be statistically different from the estimate for 2000–2001.

1.4. Measures of Substance Use Presented in This Report

Estimates based on combined 2000–2001 NHSDA data were developed using 18 measures:

past month use of any illicit drug,
past month use of marijuana,
perceptions of great risk of smoking marijuana once a month,
average annual rates of first use of marijuana,
past month use of any illicit drug other than marijuana,
past year use of cocaine,
past month use of alcohol,
past month binge alcohol use,
perceptions of great risk of having five or more drinks of an alcoholic beverage once or twice a week,
past month use of any tobacco product,
past month use of cigarettes,
perceptions of great risk of smoking one or more packs of cigarettes per day,
past year alcohol dependence or abuse,
past year alcohol dependence,
past year any illicit drug dependence or abuse,
past year any illicit drug dependence,
past year dependence on or abuse of any illicit drug or alcohol, and
past year treatment gap.

In addition, the first 12 of the above measures include estimates of change between the prevalence rates for 1999–2000 and 2000–2001. An additional 19^th measure completes the list of measures for which State estimates are presented:

past year serious mental illness.

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 often are 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 G in Volume II. The definition in this report is as follows:

Average annual incidence rate = {(Number of marijuana initiates in past 24 months) /
[(Number of marijuana initiates in past 24 months * 0.5) +
Number of persons who never used marijuana]} / 2.

In this report, this rate is expressed as a percentage or rate per 100 person years of exposure. 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 2001 to indicate first use as early as the first part of 1999 or as late as the first part of 2001. Similarly, a subject interviewed in the last part of 2001 could indicate first use as early as the last part of 1999 or as late as the last part of 2001. Therefore, in the 2001 survey, the reported period of first use ranged from early 1999 to late 2001 and was "centered" in 2000. About half of the 12 to 17 year olds who reported first use in the past 24 months reported first use in 2000, while a quarter each reported first use in 1999 and 2001. Persons who responded in 2001 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 G in Volume II. Note that only incidence rates for marijuana use are provided in this report.

1.6. Other NHSDA Reports and Products

The national results from the 2002 survey were recently released (September 2003) in two publications: (1) an overview of the findings (OAS, 2003a) and (2) a full report of results (OAS, 2003b). The name of the survey was changed in 2002 to the National Survey on Drug Use and Health in order to more accurately reflect the content of the questionnaire. In addition to the name change, other methodological changes were introduced, including a $30 incentive payment for completing the survey. Generally, analyses indicate that the changes have improved response rates and the levels of reported use of substances. However, given the changes, the new estimates are no longer comparable with NHSDA substance use estimates for 2001 and prior years—including the State estimates in this report. For a more complete discussion of the changes made and their impact on the estimates, see Appendix C in OAS (2003b). State estimates for 2002 based on the improved methodology will be published in 2004.

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:

substance dependence, abuse, and treatment (Epstein, 2002);
characteristics of recent marijuana initiates (Gfroerer, Wu, & Penne, 2002); and
risk and protective factors for substance use (using data from the 1999 NHSDA) (Wright & Pemberton, in press).

A complete listing of previously published reports from the NHSDA and other data sources is available from OAS, and many of these reports also are available through the Internet (see page ii). In addition, OAS makes public use data files available to researchers through the Substance Abuse and Mental Health Data Archive (SAMHDA, 2003). Currently, files are available from the 1979 through the 2001 NHSDAs.