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State Estimates of Substance Use and Mental Health from the
2005-2006 National Surveys on Drug Use and Health

bulletNational data      bulletState level data       bulletMetropolitan and other subState area data


1. Introduction

This report presents State estimates for 23 measures of substance use or mental health problems based on the 2005 and 2006 National Surveys on Drug Use and Health (NSDUHs) and changes in these measures between 2004-2005 and 2005-2006.1 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. Interview data from 136,110 persons were collected in 2005-2006 (Table  A.9). 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. Aggregates of these State estimates are presented as regional and national estimates. Note that these estimates are benchmarked to the national design-based estimate (for details, see Section A.4 in Appendix A). This model-based methodology provides more precise estimates of substance use at the State level than those based solely on the sample, particularly for smaller States.

Starting in 1999, the survey sample was expanded to produce State-level estimates. The samples in each State were selected to represent proportionately the geography and demography of that State. The first report with State estimates was published in 2000 (Office of Applied Studies [OAS], 2000). It utilized the 1999 survey data and the SAE procedure. Because the SAE procedure requires significant preparatory steps for the modeling and extensive computation to generate results, the number of variables estimated has been limited to ones with high policy value. The first report included only seven measures. Subsequent State reports have been published annually, gradually extending the capabilities of the SAE procedure and increasing the number of measures estimated (Wright, 2002a, 2002b, 2003a, 2003b, 2004; Wright & Sathe, 2005; Wright & Sathe, 2006; Wright, Sathe, & Spagnola, 2007). The current practice is to base annual estimates on a 2-year moving average of NSDUH data in order to enhance the precision for States with smaller samples.

State estimates also have been produced for additional measures by combining 3 (or more) years of NSDUH data and using sampling weights and direct estimation. The advantage of this approach is that it can be used on any variable in the NSDUH dataset; however, the estimates typically are not as accurate as the SAE measures. These estimates have been included in some reports and in tables on the SAMHSA website.

1.1 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.2 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 survey marked the first 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 increases 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 (2001).

The 1999 through 2001 NHSDAs and the 2002 through 2006 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.

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.

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.3 Therefore, the 2002 NSDUH was established as a new baseline for the national, as well as the State, 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 or later should not be compared with those for prior years.

By combining data across 2 years, the precision of the small area estimates for the small States, and thus their rankings, have been improved significantly. In addition, by combining 2 years of data, the impact of the national model on those States has been reduced significantly relative to estimates based on a single year's data.4

Nationally in 2005-2006, 271,112 addresses were screened and 136,110 persons responded within the screened addresses (Table  A.9). The survey is conducted from January through December each year. The screening response rate for 2005-2006 combined averaged 91.0 percent, and the interviewing response rate averaged 75.2 percent, for an overall response rate of 68.4 percent (Table  A.9). The State overall response rates for 2005-2006 ranged from 56.7 percent in New York to 77.5 percent in Utah. 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 NSDUH methodological resource books (MRBs) for each survey year (see http://oas.samhsa.gov/nsduh/methods.cfm).

1.2 Format of Report and Presentation of Data

The findings in this report are presented in six chapters, including this introductory chapter, along with U.S. maps of estimates for States at the ends of Chapters 2 through 6 and data tables in Appendices B and C at the end of the report. For serious psychological distress (SPD), estimates are provided for those aged 18 to 25, 26 or older, and 18 or older. For major depressive episode (MDE), estimates are provided for those aged 12 to 17, 18 to 25, 26 or older, and 18 or older. For all other outcomes, there are separate estimates for three age groups (12 to 17, 18 to 25, and 26 or older) and a combined estimate for those aged 12 or older. Estimates for past month alcohol use and binge alcohol use also are presented for those aged 12 to 20.

Chapter 2 presents State estimates for the prevalence of illicit drug use, marijuana use, the perceived risk of marijuana use, incidence of marijuana use, illicit drug use other than marijuana, cocaine use, and the nonmedical use of pain relievers. Chapter 3 discusses analogous estimates of alcohol use, binge alcohol use, and the perceived risk of binge alcohol use. Chapter 4 presents estimates for tobacco use, cigarette use, and the perceived risk of heavy cigarette use. Chapter 5 discusses the substance treatment–related measures (i.e., dependence on and abuse of alcohol or illicit drugs and needing but not receiving treatment). Chapter 6 presents estimates of SPD and MDE.

At the ends 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. Appendix A gives a brief description of the SAE methodology for 2005-2006. For a more detailed discussion of the SAE methodology, see Appendix E of the 2001 State report (Wright, 2003b). Also included in Appendix A are the State sample sizes and response rates for 2004, 2005, 2006, 2004-2005 combined, and 2005-2006 combined (Table s A.1 to A.12). Tables of model-based estimates for each substance use or mental health measure are included in Appendix B. The quintile rankings can be determined from these tables that include all 50 States and the District of Columbia, listed in alphabetical order, by four age categories. Estimates of change between 2004-2005 and 2005-2006 are presented in Appendix C. Estimates of change are presented for the four U.S. geographic regions in addition to State and age group. These regions, defined by the U.S. Census Bureau, consist of the following groups of States:

Northeast Region - Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, and Vermont.

Midwest Region - Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin.

South Region - Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, and West Virginia.

West Region - Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.

Tables for individual States are available on the SAMHSA website and display all of the estimates discussed in this report by the appropriate age categories (see http://oas.samhsa.gov/StatesList.cfm). Also available on the SAMHSA website are tables of the total number of persons associated with each measure corresponding to the estimated percentages or rates for each substance use or mental health measure in Appendix B (see http://oas.samhsa.gov/2k6State/toc.cfm). Estimates for all persons aged 18 or older for all 23 measures also are available on the website.

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 for each measure, 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 such ties occurred 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 average that represents the population-weighted mean of the estimates from the 50 States and the District of Columbia. These national averages 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 Montana, with a rate of 21.9 percent (Table  B.9). The 95 percent PI of that estimate is from 19.1 to 25.0 percent. Therefore, the probability is 0.95 that the true prevalence for Montana for persons aged 12 to 17 is between 19.1 and 25.0 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 provides 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 Oklahoma (6.7 percent) had the highest rate of past year nonmedical use of pain relievers among persons aged 12 or older for 2005-2006, the estimate for Arkansas (6.4 percent) was only 0.3 percentage points lower and statistically no different from Oklahoma's estimate (Table  B.8). Therefore, it is important to consider the PI when comparing States. For Oklahoma, one can say that 95 percent of the time the true value would fall in the range of approximately 5.6 to 8.1 percent. Clearly, the estimate for Arkansas falls into this range, but Hawaii's estimate (3.9 percent) does not.

Estimates of change between 2004-2005 and 2005-2006 are presented in Appendix C for 23 measures, by age group (see Table s C.1 to C.24). These tables show the estimates for 2004-2005 and 2005-2006 and a p value to test the hypothesis that there was "no change" over this period. The report discusses differences only if they are significant at p values of 0.05 or less (corresponding to a probability of 95 percent that the change was not 0). However, p values greater than 0.05 but less than or equal to 0.10 also have been marked to highlight other possible changes because the year-to-year changes are often small and relatively hard to detect, especially for those measures with low prevalence rates. The methodology for estimating change involves estimating one model for 2004-2005 based on the predictor variables and the sample for those years and a separate model for 2005-2006 based on the predictor variables and sample for those years. This methodology can lead to slightly different national models (i.e., models with slightly different model coefficients for the two sets of years). The change between 2004-2005 and 2005-2006 estimates the average yearly change between 2004 and 2006. "Average yearly change" indicates the change between 2004 and 2006 divided by 2. For more details on this topic, see Section A.10 in Appendix A on measuring change in State estimates.

Throughout the report, there are a number of related drug measures, such as marijuana use and 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 illicit drugs 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.

1.3 Measures Presented in This Report

Estimates for 2005-2006 were developed for 23 measures of substance use and mental health problems:

Estimates of change between 2004-2005 and 2005-2006 were developed for all 23 of these measures.

1.4 Other NSDUH Reports and Products

The national results from the 2006 NSDUH were released in September 2007 (OAS, 2007). Additional methodological information on the survey, including the questionnaire, is available electronically on the OAS website at http://oas.samhsa.gov/nsduh/methods.cfm. 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, 2004). 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://oas.samhsa.gov). In addition, OAS makes public use data files available to researchers through the Substance Abuse and Mental Health Data Archive (SAMHDA, 2007). Currently, data files are available for online analysis from the 1979 to 2006 NSDUHs at http://www.datafiles.samhsa.gov.

In 2006, estimates for substate planning areas based on combined 2002-2004 NSDUH data were made available at the SAMHSA website (OAS, 2006). In 2008, estimates for substate planning areas based on combined 2004-2006 NSDUH data will be available at SAMHSA's website. The substate planning area definitions for all 50 States and the District of Columbia are based on the areas for substate allocation of funds under SAMHSA's Substance Abuse Prevention and Treatment (SAPT) block grant. Substate area estimates based on combined 2004-2006 data will be available for each State and the District of Columbia for all 23 measures listed in Section 1.3. Estimates of change between 2002-2004 and 2004-2006 (when the region definitions have remained unchanged between the two time periods) also will be available for all measures that are defined the same way in both time periods. Along with the substate estimates, comparable State and national estimates will be summarized in tables. Maps that indicate the distribution of prevalence rates across the United States also will be available. The methodology used for producing substate estimates is similar to the SAE methodology used to produce the State estimates in this report.

End Notes

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

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

3 For an overview of the impact of these changes, see Section C.2 of Appendix C in OAS (2005).

4 Combining 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. Estimates of change between combined 2004-2005 data and the combined 2005-2006 data are presented in this report. This method is similar to the one used in the 2004-2005 State report (Wright et al., 2007).

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

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This page was last updated on December 30, 2008.