This report presents estimates of the prevalence of substance use in substate regions based on data from the combined 2006-2008 National Surveys on Drug Use and Health (NSDUHs). An annual survey of the civilian, noninstitutionalized population aged 12 or older, NSDUH is sponsored by the Substance Abuse and Mental Health Services Administration (SAMHSA). It collects information from persons residing in households, noninstitutionalized group quarters (e.g., shelters, rooming houses, dormitories), and civilians living on military bases. In 2006-2008, NSDUH collected data from 204,408 respondents aged 12 or older and was designed to obtain representative samples from all 50 States and the District of Columbia. The survey was planned and managed by SAMHSA's Office of Applied Studies (OAS), and data collection was conducted under contract with RTI International.1
This report marks the fourth time that detailed estimates for substate regions (also referred to as planning regions, substate areas, or regions) in all 50 States and the District of Columbia have been presented by SAMHSA. The first report to provide such estimates used data from the 1999-2001 surveys (OAS, 2005b). The second report presented estimates for 22 measures or outcomes based on the 2002-2004 NSDUHs (OAS, 2006). The third report presented estimates for 23 measures or outcomes based on the 2004-2006 NSDUHs (OAS, 2008). This report presents estimates for 21 measures of substance use based on the 2006-2008 NSDUHs among persons 12 or older. Additionally, it presents estimates for underage (12 to 20) alcohol use and binge alcohol use. These reports provide a more detailed perspective on the variations in substance use rates both within and across States than is possible with State reports (e.g., Hughes, Muhuri, Sathe, & Spagnola, 2010; Hughes, Sathe, & Spagnola, 2009).
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, see Appendix B of the 2008 NSDUH national findings report (OAS, 2009).
Estimates were generated for 362 substate regions representing collectively the 50 States and the District of Columbia (hereafter referred to as States). These regions were defined by officials from each State and were typically based on the substance abuse treatment planning regions specified by the States in their applications for the Substance Abuse Prevention and Treatment (SAPT) Block Grant administered by SAMHSA.
Section A provides a brief background on the survey, how substate regions were formed for this report, the general methodological approach, and a brief discussion of selected findings. A complete list of the 21 substance use measures presented in this report is given in Section B, which also provides further information on the small area estimation (SAE) methodology used to produce substate estimates. Section C includes tables with estimates for each of the 21 measures and the corresponding prediction intervals (PIs) for all substate regions. It also contains a set of national maps that show the prevalence of each outcome measure for each substate region. The substate regions in the tables in Section C have been ordered alphabetically within each State. There are nine separate tables, each having two or three related substance use measures. Estimates for aggregate regions (also specified by certain States) also are included in these tables. Section D contains definitions of the substate regions. Section E includes the population estimates for persons aged 12 or older and the combined 2006, 2007, and 2008 NSDUH sample sizes and response rates for each substate region. Users may find the population estimates helpful in calculating the weighted average prevalence estimate for any combination of substate regions or to determine the number of people using a particular substance in a substate region. For example, the number of persons aged 12 or older who used marijuana in the past month in Alabama's Region 1 (41,025 persons) could be obtained by multiplying the prevalence rate from Table C2 (3.8 percent—shown as 3.84 percent in the table) and the population estimate from Table E1 (1,068,369). Section F lists the references, and Section G provides a list of contributors to the production of this report.
The substate regions for each State were developed for this report in a series of communications between SAMHSA staff and State treatment representatives in late 2009. The goal of the project was to provide substate-level estimates showing the geographic distribution of substance use prevalence for regions that States would find useful for treatment planning purposes.2 The final substate region boundaries were based on the State's recommendations, assuming that the NSDUH sample sizes were large enough to provide estimates with adequate precision. Most States defined regions in terms of counties or groups of counties. A few States defined the regions in terms of census tracts. Several States also requested estimates for aggregate planning regions along with the estimates for their substate planning regions. An aggregate planning region is made up of two or more substate planning regions. A few of these States wanted the maps to be produced for the aggregate regions instead of their substate planning regions. For example, New York has 15 substate regions, and those 15 regions were combined to create 4 aggregate regions that are used in the maps. Hence, for each measure in this report, maps were produced for 344 planning regions and not for 362 regions. The discussion of findings in this section (Section A.5) also is restricted to these 344 planning regions.
These 344 substate regions used in the maps were ranked from lowest to highest for each measure and were divided into 7 categories designed to represent distributions that are somewhat symmetric, like a normal distribution. Colors were assigned to all regions such that the third having the lowest prevalence are in blue (115 regions), the middle third are in white (114 regions), and the third with the highest prevalence are in red (115 regions). The only exceptions were the three perception-of-risk outcomes, which have the highest estimates represented in blue and the lowest represented in red. To further discriminate among the regions that display relatively higher prevalence, the "highest" third has been further divided into 3 categories: dark red for the 15 substate regions with the highest estimates, medium red for the 31 substate regions with the next highest estimates, and light red for the 69 substate regions in the third highest group. The "lowest" third is categorized in a similar way using three distinct shades of blue. Because of tied values of prevalence, the number of substate regions in each category may vary a little.
In addition to the tables provided in this report, other substate region tables will be available on SAMHSA's Web site. Besides the tables on the 21 measures presented in this report, the age group tables will show estimates for major depressive episode (MDE) for youths aged 12 to 17. The following sets of tables will appear on SAMHSA's Web site:
These additional tables will be posted at http://samhsa.gov/data/substate.cfm as they become available.
Estimates in this report are based on hierarchical Bayes estimation methods that combine survey data with a national model. Applying this methodology to the State substance use measures has been shown to result in more precise estimates than using the sample-based results alone (Wright, 2002). The methodology used to produce estimates in this report is the same as that used to produce State estimates from the NSDUH data since 1999 and has been used for prior substate reports (see Hughes et al., 2010; OAS, 2008). Sample data have been combined across 3 years (2006-2008) in this report to improve the precision of substate region estimates. The estimate for each region is accompanied by a 95 percent prediction interval (for more details, see Section B, Substate Region Estimation Methodology).
In addition to the substate region estimates, comparable estimates are provided for the 50 States and the District of Columbia using the same methodology. Because these estimates are based on 3 consecutive years of data, they are not directly comparable with the State estimates in earlier reports that are based on only 2 consecutive years. Estimates for the Nation and the four census regions also are presented. These regions, defined by the U.S. Census Bureau, are defined as follows:
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.
Because the small area estimation methods used here tend to borrow strength from both the national model and the State-level random effects, estimates for substate regions with sample sizes that were closer to the minimum (200) tend to be shrunk more toward the corresponding State prevalence estimate than substate regions with large sample sizes. This methodology tends to cluster the small sample substate estimates around their State means. Thus, relatively high estimates for small substate regions tend to shrink toward the State mean, while relatively low estimates tend to increase toward the State mean. On the other hand, for regions with large sample sizes, the methodology produces estimates that are close to the weighted average of the sample data. In addition, these estimates are design consistent so that as the sample size for a substate region increases, the estimate approaches the true population value.
For the 2002 NSDUH, a number of methodological changes were introduced, including a $30 incentive for participating in the survey, additional training for interviewers to encourage adherence to survey protocols, a change in the survey name, and a shift to the 2000 decennial census (from the 1990 census) as a basis for population counts used in estimation. An unanticipated result of these changes was that the prevalence rates for 2002 were in general substantially higher than those for 2001. These rates were substantially higher than could be attributable to the usual year-to-year trend. Additional information on these methodological changes is available in OAS (2005a).
Because of the changes in the survey that took place in 2002, estimates for 2006-2008 are not comparable with estimates for 1999-2001, and it is not possible to separate the effect of the methodological changes from the true trends in substance use. Therefore, one should not conclude that any differences between estimates from 1999-2001 and 2006-2008 represent true changes. However, estimates from 2002-2004, 2004-2006, and 2006-2008 are comparable for outcomes that were defined in a similar manner and for substate regions defined consistently across these time periods.
Six States made changes to their 2004-2006 substate regions for producing the 2006-2008 estimates: Florida, Louisiana, Michigan, Nebraska, Oregon, and Virginia. Each of these States had at least one substate region definition that was the same as the 2004-2006 definition. The remaining 44 States and the District of Columbia did not change their definitions of substate regions or aggregate regions.
Based on NSDUH data from the 2006-2008 surveys combined, 8.1 percent of persons in the United States aged 12 or older had used an illicit drug in the past month. Northwest Iowa reported the lowest rate at 4.2 percent, and Region 1 (Multnomah) in Oregon had the highest rate at 14.9 percent. The 15 substate regions with the highest rates were dispersed among 11 States: Alaska (Rural), California (Region 10), Colorado (Regions 2 and 7), Delaware (Wilmington City), the District of Columbia (Ward 1, Ward 2, Ward 5, and Ward 8), Massachusetts (Boston), Michigan (Detroit City), Montana (Region 5), Oregon (Region 1 [Multnomah]), Rhode Island (Bristol and Newport; and Providence), and Vermont (Champlain Valley). Of the 15 substate regions with the lowest rates of illicit drug use in the past month, 7 regions were from 3 Midwestern States: Iowa, Kansas, and North Dakota. Moreover, Pennsylvania had 3 substate planning regions (Regions 5, 18, 23, 24, and 46; Regions 29 and 34; and Regions 19, 26, 28, and 42), Texas had 2 regions (Region 10 and Region 11), and Utah had 2 regions (Central, Four Corners, San Juan, and Southwest; and Utah County) among the 15 with the lowest rates of past month illicit drug use.
Marijuana is the most commonly used illicit drug, and many of the substate regions having a high rate of illicit drug use reported similarly high rates of marijuana use. The national rate of past month marijuana use was 6.0 percent in 2006-2008. The lowest rate occurred in Iowa's Northwest region (2.9 percent). The highest rate was found in Rhode Island's Bristol and Newport region (12.2 percent). The lowest group for past month marijuana use had 12 regions that were the same as those for past month illicit drug use, and 11 of the highest 15 substate regions for past month marijuana use were the same as those for past month illicit drug use.
In 2006-2008, 38.3 percent of persons aged 12 or older in the Nation perceived a great risk in smoking marijuana once a month. Substate regions with low rates suggest that a larger percentage of the population do not think that smoking marijuana once a month is a great risk compared with regions with higher rates. The lowest rate was in District of Columbia's Ward 3 (18.5 percent), which was 1 of 3 substate regions in the District of Columbia that were among the regions with the 15 lowest rates. Other States with more than 1 region in the lowest 15 include Massachusetts and New Hampshire (3 regions each), and Oregon and Washington (2 regions each). The highest rate was in Mississippi's Region 5 (54.5 percent). Mississippi had 5 substate regions among the 15 with the highest rates. Other States with multiple substate regions in the top 15 included Pennsylvania and Texas, each with 2 regions.
Most recent marijuana initiates (i.e., those who used marijuana for the first time in the past year) were younger than 18 when they first used (OAS, 2009, p. 54). Nationwide, 1.6 percent of persons aged 12 or older had used marijuana for the first time in 2006-2008. Of the 14 regions in the highest group for first-time marijuana use, 6 regions were also in the highest group for past month marijuana use: Alaska (Rural), District of Columbia (Ward 2), Florida (Circuit 2), Rhode Island (Bristol-Newport), and Vermont (Champlain Valley and Rural Southeast).
Nationally, 3.7 percent of persons aged 12 or older had used an illicit drug other than marijuana in 2006-2008 in the past month. Illicit drugs other than marijuana include cocaine (and crack), heroin, hallucinogens, inhalants, or prescription-type psychotherapeutics used nonmedically. The nonmedical use of prescription-type psychotherapeutics includes the nonmedical use of pain relievers, tranquilizers, stimulants, or sedatives and does not include over-the-counter drugs or new methamphetamine items that were added to the NSDUH questionnaire in 2005 and 2006. Past month use of these substances ranged from a low of 2.1 percent in the Lake Region and South Central area of North Dakota to a high of 6.3 percent in the Providence substate region of Rhode Island. All 15 regions in the country with the lowest rates of use of an illicit drug other than marijuana in the past month were from Midwestern States (6 regions in Iowa, 4 in North Dakota, and 5 in South Dakota). Of the 15 substate regions with the highest rates, 8 regions were in the South (2 each in Arkansas and West Virginia, 3 in the District of Columbia, and 1 in Tennessee).
The national prevalence rate for the use of cocaine in the past year among persons aged 12 or older was 2.3 percent in 2006-2008 and ranged from 1.1 percent in Region 6 of South Dakota to 6.4 percent in the District of Columbia's Ward 2. Among the 15 substate regions with the highest rate of past year cocaine use, 8 were in the District of Columbia (Wards 1 to 8), and 4 were in Rhode Island (Bristol-Newport, Kent, Providence, and Washington). Regions with the lowest rates of past year cocaine use included 5 in Mississippi, 3 regions each from North Dakota and South Dakota, and 2 in Idaho.
During 2006-2008, 5.0 percent of all persons aged 12 or older had used a pain reliever for nonmedical use within the past year. Estimates ranged from 3.1 percent in the District of Columbia's Ward 7, Maryland's Prince George's region, and New Jersey's Northern region to 7.9 percent in Oklahoma's Oklahoma County and East Central regions. Of the 15 regions with the highest prevalence rates, 6 were from Oklahoma and 3 regions each were from Arkansas and Tennessee. Regions with the 15 lowest rates included 3 in the District of Columbia (Wards 4, 7, and 8) and 2 regions each from Florida, Maryland, New Jersey, and South Dakota.
Alcohol is the most commonly used substance in the United States. Nationally, about half (51.2 percent) of Americans aged 12 or older reported past month use of alcohol in 2006-2008. Utah County, Utah, had the lowest rate of any region in the Nation (17.6 percent). The District of Columbia (Ward 3) had the highest rate (81.2 percent). Among the 15 substate regions with the highest rates, 4 States each had 2 or more regions in this group: Connecticut (South Central and Southwest), the District of Columbia (Ward 1, Ward 2, and Ward 3), Minnesota (Region 7A [Hennepin] and Region 7C), and Rhode Island (Bristol-Newport and Washington). Of the 15 substate regions with the lowest rates of past month alcohol use, 12 were distributed across 4 States: Kentucky (2 regions), Mississippi (3 regions), Utah (5 regions), and West Virginia (2 regions).
Binge alcohol use is defined as drinking five or more drinks on the same occasion (i.e., at the same time or within a couple hours of each other) on at least 1 day in the 30 days prior to the survey. Nationally, past month binge alcohol use was reported by 23.3 percent of persons aged 12 or older during 2006-2008. Utah County, Utah, once again had the lowest rate (10.6 percent), while the highest rate was in Ward 2 in the District of Columbia (42.7 percent). Of the 15 substate regions with the lowest rates of past month binge alcohol use, 12 were distributed across 4 States: Kentucky (2 regions), Mississippi (2 regions), Utah (all 6 regions), and West Virginia (2 regions). Of the 15 substate regions with the highest rates of binge drinking, 11 were distributed across 4 States: District of Columbia (3 regions), Minnesota (2 regions), North Dakota (4 regions), and Wisconsin (2 regions).
In 2006-2008, 42.0 percent of persons aged 12 or older in the Nation perceived a great risk in having five or more drinks of an alcoholic beverage once or twice a week. Substate regions with low rates suggest that a larger percentage of the population do not think that this pattern of drinking is a great risk compared with regions with higher rates. The lowest rate was in New Hampshire's Northern region (32.1 percent), and the highest rate was in Utah's Utah County (56.1 percent). New Hampshire had 3 regions and the District of Columbia, Massachusetts, Minnesota, South Dakota, and Wisconsin each had 2 regions among the 15 substate regions with the lowest rates. Substate regions in the top 15 with the highest rates included 4 in Utah and 2 each in the District of Columbia, Mississippi, New Mexico, and Texas.
The national rate of underage alcohol use in the past month (i.e., past month use of alcohol among persons aged 12 to 20) was 27.5 percent in 2006-2008. The lowest rate occurred in Utah County, Utah (11.1 percent), while the highest rate occurred in the District of Columbia's Ward 2 (66.9 percent). Of the 15 substate regions with the lowest rates of past month underage alcohol use, 9 were in the West (1 in Alaska, 2 in Idaho, and 6 in Utah). Among the 15 substate regions with the highest rates of past month underage alcohol use, 8 were in the Northeast (1 in New Hampshire, 1 in New York, 3 in Rhode Island, and 3 in Vermont).
Nationally, the rate of underage binge drinking during the past month was 18.3 percent in 2006-2008. The lowest rate of past month underage binge alcohol use occurred in Michigan's Detroit City (9.7 percent), and the highest rate was in the District of Columbia's Ward 2 (51.9 percent). Of the 15 substate regions with the lowest rates of underage binge drinking, 9 regions were from 4 States: District of Columbia (Ward 7 and Ward 8), Mississippi (Region 2 and Region 5), South Carolina (Region 1 and Region 3), and Utah (Central, Four Corners, San Juan, and Southwest; Davis County; and Utah County). Of the 15 substate regions with the highest rates of underage binge drinking, 8 regions were in 4 States: District of Columbia (Ward 2 and Ward 3), New Hampshire (Central and Northern), North Dakota (Northeast and Southeast), and Rhode Island (Bristol-Newport and Washington).
In 2006-2008, 29.0 percent of all persons aged 12 or older used a tobacco product in the past month. Tobacco products include cigarettes, smokeless tobacco (i.e., chewing tobacco or snuff), cigars, or pipe tobacco. Tobacco is the second most commonly used substance in the United States next to alcohol. The lowest rate of past month tobacco use occurred in Utah County, Utah (13.6 percent). The highest rate was in Kentucky's Adanta, Cumberland River, and Lifeskills region (44.0 percent). Of the 15 substate regions with the lowest rates of past month tobacco use, 11 regions were in 3 States: California (4 regions), Maryland (2 regions), and Utah (5 regions). Among the 15 substate regions with the highest rates of past month tobacco use, 12 regions were in 5 States: Arkansas (2 regions), Kentucky (3 regions), Tennessee (2 regions), West Virginia (3 regions), and Wyoming (2 regions).
During 2006-2008, the national rate of past month cigarette use among persons aged 12 or older was 24.6 percent. As with past month use of tobacco, the highest rate of past month cigarette use was in Kentucky's Adanta, Cumberland River, and Lifeskills region (36.0 percent), and the lowest rate was in Utah County, Utah (11.9 percent). The majority of the 15 substate regions with the highest rates of past month cigarette use were in Arkansas (3 regions), Kentucky (3 regions), Missouri (2 regions), and West Virginia (2 regions). Of the 15 substate regions with the lowest rates of past month cigarette use, 4 regions were in California, 3 were in Maryland, and 5 were in Utah; most of these regions were among the 15 with the lowest rates of past month tobacco use.
In 2006-2008, 73.7 percent of persons aged 12 or older in the Nation perceived a great risk in smoking one or more packs of cigarettes per day. Substate regions with low rates suggest that a larger percentage of the population do not think that smoking one or more packs of cigarettes is a great risk compared with regions with higher rates. The lowest rate was in Kentucky's Kentucky River, Mountain, and Pathways region (61.9 percent), and the highest rate was in the District of Columbia's Ward 3 (81.4 percent). Ohio had 4 substate regions, Kentucky and Wisconsin each had 3 substate regions, and Missouri had 2 regions among the 15 with the lowest rates. States with multiple regions in the top 15 include Connecticut (2 regions), the District of Columbia (5 regions), and New York (2 regions).
Several series of questions to assess the prevalence of substance use disorders (i.e., dependence on or abuse of a substance) in the past 12 months are included in NSDUH each year. Substances include alcohol and illicit drugs, such as marijuana, cocaine, heroin, hallucinogens, and inhalants, and the nonmedical use of prescription-type psychotherapeutic drugs. These series of questions are used to classify persons as being dependent on or abusing specific substances based on criteria specified in the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) (American Psychiatric Association [APA], 1994). The questions on dependence ask about health and emotional problems, attempts to cut down on use, tolerance, withdrawal, and other symptoms associated with substances used. The questions on abuse ask about problems at work, home, and school; problems with family or friends; physical danger; and trouble with the law due to substance use. Dependence reflects a more severe substance problem than abuse, and persons are classified with abuse of a particular substance only if they are not dependent on that substance.
Nationally, 7.5 percent of the population aged 12 or older was classified with being dependent on or having abused alcohol in the past year in 2006-2008. Past year alcohol dependence or abuse varied from a low of 4.8 percent in Pennsylvania (Regions 19, 26, 28, and 42) to a high of 14.6 percent in the District of Columbia (Ward 2). Colorado, the District of Columbia, Minnesota, Montana, North Dakota, and South Dakota all had more than 1 of its substate regions in the highest 15.
In 2006-2008, 2.8 percent of persons aged 12 or older were dependent on or had abused illicit drugs in the past year. The rates among substate regions ranged from a low of 1.5 percent in Pennsylvania's Regions 19, 26, 28, and 42 and in Pennsylvania's Regions 5, 18, 23, 24, and 46 to 6.7 percent in the District of Columbia's Ward 5. The District of Columbia accounted for 6 of the top 14 substate regions with dependence on or abuse of illicit drugs in the past year. Only 2 of the top 15 substate regions for alcohol dependence or abuse were also in the top 14 for illicit drug dependence or abuse: the District of Columbia's Ward 1 and Ward 2.
The national rate in 2006-2008 for past year dependence on or abuse of illicit drugs or alcohol among persons aged 12 or older was 9.1 percent. Substate regions that were ranked high for past year dependence on or abuse of alcohol also tended to be ranked high for dependence on or abuse of illicit drugs or alcohol because alcohol accounts for most of the substance dependence or abuse. For example, 10 of the top 15 substate regions for alcohol dependence or abuse were in the top 15 for illicit drug or alcohol dependence or abuse. Ward 2 in the District of Columbia had the highest rate of illicit drug or alcohol dependence or abuse (16.1 percent), and Regions 19, 26, 28, and 42 in Pennsylvania had the lowest rate in the Nation (5.3 percent).
The definition of a person needing but not receiving treatment for an illicit drug use problem is that the person meets the criteria for abuse of or dependence on illicit drugs according to the DSM-IV, but has not received specialty substance use treatment for an illicit drug problem in the past year. Specialty substance use treatment is treatment received at a drug or alcohol rehabilitation facility (inpatient or outpatient), hospital (inpatient only), or mental health center. In 2006-2008, 2.5 percent of persons aged 12 or older needed treatment for an illicit drug use problem in the past year, but did not receive it. The lowest rate in the Nation (1.4 percent) occurred in Pennsylvania's Regions 19, 26, 28, and 42 and in Pennsylvania's Regions 5, 18, 23, 24, and 46. The region with the highest rate in the Nation was Ward 8 in the District of Columbia (5.1 percent). Among the top 15 substate regions with the highest rates of needing but not receiving treatment for illicit drug use problems, 11 were clustered in 3 States: 3 regions in California, 5 regions in the District of Columbia, and 3 regions in Ohio.
In 2006-2008, the percentage of persons aged 12 or older who needed but did not receive treatment for alcohol use problems (7.2 percent) was nearly 3 times as large as the percentage of persons needing but not receiving treatment for illicit drug use problems (2.5 percent). Generally, the substate regions with the highest rates of untreated alcohol use problems were not the same as those regions with the highest rates of untreated illicit drug use problems. Only Ward 1 and Ward 2 of the District of Columbia and Region 5 of Montana were in the top group for both measures. The District of Columbia's Ward 2 had a rate of 14.2 percent, the highest in the Nation, and Pennsylvania's Regions 19, 26, 28 and 42 had the lowest rate (4.5 percent).
In Section A.5, a discussion covering most of the 21 substance use measures shown in Section C was presented. This discussion was primarily limited to providing the range of rates from lowest to highest in the Nation and any State-level clustering of substate regions in the lowest or the highest group of substate regions. It is important to note that these estimates are based on a sample, and that different samples could result in slightly different high and low regions. For example, Oregon's Region 1 (Multnomah County) had the highest rate of past month illicit drug use (14.9 percent) of any substate region in the Nation. It can be stated with 95 percent confidence that the true value falls between 11.8 and 18.7 percent (see Table C1). Estimates in the highest group ranged from 12.0 percent in Colorado's Regions 2 and 7 to 14.9 percent in Multnomah County in Oregon; therefore, Multnomah County's estimate of past month illicit drug use may not be any different from estimates shown in the other regions in the highest group.
The tables presented in Section C contain estimates for 362 substate regions, 22 aggregated substate regions, 50 States and the District of Columbia, 4 census regions, and the total United States. The national maps included in that section display 344 substate regions (a combination of substate regions and aggregate substate regions) to satisfy requests made by some States to only show aggregate substate regions (see Section D). The discussion in Section A.5 is based only on these 344 substate or aggregate substate regions.
1 RTI International is a trade name of Research Triangle Institute.
2 These substate regions were defined by officials from each State, typically based on the substance abuse treatment planning regions specified by States in their applications for an SAPT Block Grant administered by SAMHSA. There is extensive variation in treatment planning regions across States. In some States, the planning regions are used more for administrative purposes rather than for planning purposes. Because the estimation method required a minimum NSDUH sample size of approximately 200 to provide adequate precision, planning regions with sample sizes that were much smaller than that were collapsed with adjacent regions until an adequate sample size was obtained.
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