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1. Introduction

This report presents State estimates for 22 measures of substance use or mental health problems based on the 2007 and 2008 National Surveys on Drug Use and Health (NSDUHs) and determines whether changes in these measures between 2006-2007 and 2007-2008 are statistically significant. 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 136,606 persons were collected in 2007-2008 (see Table A.9 in Appendix A). 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.5 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 States with smaller samples.

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 outcome measures 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 (Hughes, Sathe, & Spagnola, 2008, 2009; Wright, 2002a, 2002b, 2003a, 2003b, 2004; Wright & Sathe, 2005, 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 multiple 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 estimates based on the SAE methods. These estimates have been included in some reports and in tables on the SAMHSA Web site.

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 Office of Applied Studies (OAS), and the data are collected and processed by RTI International through a contract with OAS.1 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 National Household Survey on Drug Abuse (NHSDA, the former name of NSDUH), see OAS (2001).

The 1999 through 2001 NHSDAs, and the 2002 through 2008 NSDUHs employed a 50-State design with an independent, multistage area probability sample for each of the 50 States and the District of Columbia. For the 50-State design, 8 States were designated as large sample States (California, Florida, Illinois, Michigan, New York, Ohio, Pennsylvania, and Texas) with target sample sizes of 3,600 per year or 7,200 over a 2-year period. In 2007-2008, sample sizes in these States ranged from 7,113 to 7,482 (Table A.9). For the remaining 42 States and the District of Columbia, the target sample size was 900 per year or 1,800 over a 2-year period. Sample sizes in these States ranged from 1,724 to 1,927 in 2007-2008. This approach ensures there is sufficient sample in every State to support SAE while at the same time maintaining efficiency for national estimates. 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—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 national, as well as the State estimates. Given the varying effects of the incentive and other changes, 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 sample 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.3

Nationally in 2007-2008, 284,425 addresses were screened and 136,606 persons responded within the screened addresses (see Table A.9 in Appendix A). The survey is conducted from January through December each year. The screening response rate (SRR) for 2007-2008 combined averaged 89.3 percent, and the interview response rate (IRR) averaged 74.2 percent, for an overall response rate (ORR) of 66.2 percent (Table A.9). The ORRs for 2007-2008 ranged from 50.8 percent in New York to 75.1 percent in South Dakota. 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://www.samhsa.gov/data/nsduh/methods.htm).

The weighted SRR is defined as the weighted number of successfully screened households (or dwelling units)4 divided by the weighted number of eligible households, or

Capital S R R is equal to the ratio of two quantities. The numerator is the summation of the product of w sub h h and complete sub h h. The denominator is the summation of the product of w sub h h and eligible sub h h.

where whh is the inverse of the unconditional probability of selection for the household and excludes all adjustments for nonresponse and poststratification.

At the person level, the weighted IRR is defined as the weighted number of respondents divided by the weighted number of selected persons, or

Capital I R R is equal to the ratio of two quantities. The numerator is the summation of the product of w sub i and complete sub i. The denominator is the summation of the product of w sub i and selected sub i.

where wi is the inverse of the probability of selection for the person and includes household-level nonresponse and poststratification adjustments. To be considered a completed interview, a respondent must provide enough data to pass the usable case rule.5

The weighted ORR is defined as the product of the weighted SRR and the weighted IRR or

Capital O R R is equal to the product of capital S R R and capital I R R.

1.2 Format of Report and Presentation of Data

This report has seven chapters, including this introductory chapter. Chapters 2 through 6 discuss the findings of the 2007-2008 State small area estimates and comparisons between 2006-2007 and 2007-2008, along with U.S. maps of estimates for States at the end of each chapter. A separate chapter (Chapter 7) on comparisons between 2002-2003 and 2007-2008 also is included in this report. Appendix A presents the State estimation methodology. Data tables are presented in Appendices B, C, and D. Appendix E includes a discussion on other sources of State-level data. Information on the contributors to this report is provided in Appendix F.

To address SAMHSA's need for estimates of serious mental illness (SMI), several important changes were made to the adult mental health section in the 2008 NSDUH questionnaire. These questionnaire changes caused discontinuities in trends for major depressive episode (MDE) and serious psychological distress (SPD) among adults aged 18 or older; thus, these measures are not included in this report. Further analysis is needed to better understand the nature of the changes in the reporting of SPD and MDE associated with questionnaire differences. These analyses may lead to the development of statistical adjustments to provide comparable estimation and more complete trend measurement. For more information about these changes, please see Appendix B of the 2008 NSDUH national findings report (OAS, 2009).

No questionnaire changes were made in 2008 that affected MDE items for youths aged 12 to 17; therefore, estimates in Chapter 6 are provided only for persons in that age group. 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 of 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 of tobacco use, cigarette use, and the perceived risk of heavy cigarette use. Chapter 5 discusses the substance use disorder and treatment need–related measures (i.e., dependence on and abuse of alcohol or illicit drugs and needing but not receiving treatment). Chapter 6 presents estimates of MDE among persons aged 12 to 17. In Chapters 2 through 6, changes in estimates between 2006-2007 and 2007-2008 are discussed. Chapter 7 discusses changes between 2002-2003 and 2007-2008 for selected outcomes. This is a new chapter that is included to look at changes in State estimates over a longer period of time than in prior State reports.

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 describes the SAE methodology for 2007-2008. For more details on 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 2006, 2007, 2008, 2006-2007 combined, and 2007-2008 combined (Tables A.1 to A.12). Sample sizes and response rates for 2002, 2003, and 2002-2003 combined are available in Appendix A of the 2002-2003 SAE report (Wright & Sathe, 2005). 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 4 age categories. Tables comparing the 2006-2007 and 2007-2008 estimates are presented in Appendix C. Comparisons of 2002-2003 and 2007-2008 estimates are presented in Appendix D. Note that because the layout of the tables in Appendix C and Appendix D is very similar, we have deliberately used a larger font for the years in the titles of these tables so that a reader can quickly distinguish between the two. Tables comparing estimates over various time periods are presented for the four U.S. geographic regions in addition to State and age groups. 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 Web site and display all of the estimates discussed in this report by the appropriate age categories (see http://www.samhsa.gov/data/StatesList.htm). Also available on the SAMHSA Web site 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://www.samhsa.gov/data/2k8State/toc.htm). Estimates for all persons aged 18 or older for 21 of the 22 measures (excluding past year MDE) are also available on the Web site.

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.5.) 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 rate of past month use of marijuana for young adults aged 18 to 25 was Rhode Island, with a rate of 30.3 percent and a 95 percent PI that ranged from 26.5 to 34.4 percent (Table B.3). Therefore, the probability is 0.95 that the true prevalence of past month marijuana use for Rhode Island for persons aged 18 to 25 is between 26.5 and 34.4 percent. The PI generated for this report indicates the uncertainty due to both sampling variability and model bias and is also referred to as a credible interval. A credible interval is an interval that contains a given percentage of the posterior distribution of the parameter (or measure) of interest. Please note that the PIs have been generated (in a different manner) in other applications to estimate future values of a parameter of interest; however, that interpretation does not apply to this report.

In this report, State rankings are discussed in terms of the range because the latter provides a useful context for the discussion. When comparing two State prevalence rates, two overlapping 95 percent PIs do not imply that their State prevalence rates are statistically equivalent at the 5 percent level of significance. For details on a more accurate test to compare State prevalence rates, see Section A.11 in Appendix A.

Comparisons between 2006-2007 and 2007-2008 are presented in Appendix C for 22 measures, by age group (see Tables C.1 to C.23). These tables show the estimates for 2006-2007 and 2007-2008 and a p value corresponding to a test of 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. However, p values greater than 0.05 but less than or equal to 0.10 also have been marked on tables to highlight other possible changes that may be of interest despite not reaching statistical significance. The methodology for testing for change involves estimating one model for 2006-2007 based on the predictor variables and the sample for those years and a separate model for 2007-2008 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 2006-2007 and 2007-2008 estimates the average yearly change between 2006 and 2008. "Average yearly change" indicates the change between 2006 and 2008 divided by 2. For more details on this topic, see Section A.12 in Appendix A on measuring change in State estimates.

Comparisons between 2002-2003 and 2007-2008 are presented in Appendix D for 21 measures, by age group (see Tables D.1 to D.22). For details on how significance testing is done, see Section A.12. Information on other sources of State-level estimates is provided in Appendix E. This appendix briefly describes the Behavioral Risk Factor Surveillance System (BRFSS).

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 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 been estimated with different models (and not jointly in one model), subtracting one measure from another related measure at the State level can give misleading results, perhaps even a "negative" estimate, and should be avoided.

1.3 Measures Presented in This Report

Estimates for 2007-2008 were developed for 22 measures of substance use and mental health problems:

Tests of change between 2006-2007 and 2007-2008 were produced for all 22 measures, and tests of change between 2002-2003 and 2007-2008 were developed for 21 of these measures (for all except MDE).

1.4 Other NSDUH Reports and Products

The national results from the 2008 NSDUH were released in September 2009 (OAS, 2009). Additional methodological information on the survey, including the questionnaire, is available electronically on the OAS Web site at http://www.samhsa.gov/data/nsduh/methods.htm. Brief descriptive reports and in-depth analytic reports focusing on specific issues or population groups also are produced by OAS. Further information on accessing 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://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). Currently, data files are available for online analysis from the 1979 to 2008 NSDUHs at http://www.datafiles.samhsa.gov.

In 2010, estimates for substate planning areas based on combined 2006-2008 NSDUH data will be available on the SAMHSA Web site at http://www.samhsa.gov/data/metro.htm. 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 2006-2008 data will be available for each State and the District of Columbia for all 22 measures listed in Section 1.3. Comparisons between 2004-2006 and 2006-2008 (when the region definitions 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 along with maps that indicate the distribution of prevalence rates across the United States. 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 RTI International is a trade name of Research Triangle Institute, Research Triangle Park, North Carolina.

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

3 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. Comparisons between the combined 2006-2007 data and the combined 2007-2008 data are presented in this report. This method is similar to the one used in the 2004-2005, 2005-2006, and 2006-2007 State reports (Hughes et al., 2008, 2009; Wright et al., 2007).

4 A successfully screened household is one in which all screening questionnaire items were answered by an adult resident of the household and either zero, one, or two household members were selected for the NSDUH interview.

5 The usable case rule requires that a respondent answer "yes" or "no" to the question on lifetime use of cigarettes and "yes" or "no" to at least nine additional lifetime use questions.

6 For details on how the average annual rate of first use of marijuana (incidence of marijuana) is calculated, see Section A.7 of Appendix A.

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