The 2002 National Survey on Drug Use and Health (NSDUH) represents a new baseline year as a result of numerous changes, including a $30 incentive for participation, improved standards for interview protocol, and a change in the survey name from the National Household Survey on Drug Abuse (NHSDA) to its current name. These changes increased the overall national response rate from 2001 to 2002 by 3.9 percent and as much as 10.7 percent in one State. Partly because of the increased response rates, but also because of reporting differences, prevalence estimates for most substances are significantly higher in 2002 than in 2001—more than could be attributed to secular trends in drug use. Therefore, it is difficult to draw any conclusions by looking at the changes in prevalence rates between 2000–2001 and 2002 because the true trend cannot be separated from the methodological effects. For this reason, the 2002 estimates should not be compared with estimates from prior years. Because of the uneven effects of the incentive and other methodological changes on the State response rates and prevalence rates, one should not compare State rankings for 2002 with those for prior years either.
Chapters 2 through 6 of this report describe the variations across the States in each of the 20 measures for which estimates were produced based on the 2002 NSDUH. This chapter provides a summary of some of the most important findings, including a discussion of similarities and differences in patterns across different measures, in the context of prior research on the relationships between these measures at the individual level. Also included in this chapter is information on the quality of these estimates.
State estimates of the prevalence of substance use can provide, among other things, information on the regional clustering of these rates. Many factors can influence State prevalence rates, including local culture and social norms, State and local policies, and the sources, supply, and marketing of drugs. The findings in this report reveal varying degrees of clustering of substance use depending on the substance.
States with the highest prevalence of illicit drug use for persons aged 12 or older include six States in the West, three Northeastern States, and the District of Columbia. The lowest fifth included States from all regions except the Northeast (Figure 2.1). There was similar clustering associated with alcohol use among the States, with the highest rates for persons aged 12 or older, which included six Northeastern States, as well as Colorado, District of Columbia, Maryland, and Minnesota. However, all of the States in the lowest fifth for alcohol use among persons aged 12 or older, except for Utah, were in the South (Figure 3.1). Cigarette use was clustered mostly in the South and a few contiguous Midwestern States (Indiana, Missouri, and Ohio) (Figures 4.5 to 4.8). The highest rates of both binge alcohol use and general alcohol use were found in Northern States (Figures 3.1 to 3.8). The highest rates of past month cigarette and tobacco use were in the South (Figures 4.1 to 4.8). In general, the lower the prevalence rate of a substance, the lower the regional clustering.
Substance use epidemiology has documented the inverse relationship between the perceptions of risk in using a substance and the actual use of the substance at the individual level (e.g., Bachman et al., 1998). The lower the perception that use involves risk, the higher the probability of use. This relationship at the individual level is reflected to varying degrees in correlations at the State level. Binge alcohol use provides an example of a "weak" relationship at the State level. Six out of ten States with the lowest percentages of perceived risk of binge drinking among persons aged 12 or older reported the highest levels of binge alcohol use (Figures 3.5 and 3.9). A similar relationship occurred between past month binge use of alcohol and past month use of alcohol in general among persons aged 12 or older, with four of the States that ranked highest in past month binge alcohol use also ranking highest in past month alcohol use (Figures 3.1 and 3.5).
A slightly stronger relationship was found between perceived risk of occasional use of marijuana and past month use of marijuana among persons aged 12 or older. Seven of the States with the lowest perceived risk of occasional marijuana use also had the highest rates of past month use of marijuana (Figures 2.5 and 2.9). The strength of the relationship between the perception of risk and prevalence of use of cigarettes among persons aged 12 or older fell somewhere between perceived risk of binge use of alcohol and perceived risk of occasional use of marijuana. Six States that had high rates of cigarette use also had the lowest rates of perceived risk of heavy use of cigarettes; seven States that had low rates of cigarette use also had the highest rates of perceived risk of heavy cigarette use (Figures 4.5 and 4.9).
Because marijuana is the most commonly used illicit drug, all of the 10 States with the highest rates of illicit drug use also were the States with the highest rates of past month marijuana use in the 12 or older population (Figures 2.1 and 2.5). States where the rate of first-time use of marijuana was high also tended to be States with the highest rates of past month marijuana use (Figures 2.5 and 2.13).
Of the 10 States in the top fifth with respect to past month use of an illicit drug for persons aged 12 or older, 6 were in the top fifth for past month use of an illicit drug other than marijuana (Figures 2.1 and 2.17). Only five of the States with the highest levels of past month use of illicit drugs other than marijuana for persons aged 12 or older also had the highest rates of past year use of cocaine (Figures 2.17 and 2.21). In general, a State that had a high level of use of one substance also tended to have high levels of use of related substances.
States that ranked high for substance use by all persons aged 12 years or older also ranked high in use of substances by the population aged 26 or older. This relationship derives from the fact that the latter group represents 77 percent of the total population 12 years old or older. Although the 26 or older age group often drove the prevalence rates in the 12 or older population in a State, rates among the 12 to 17 and 18 to 25 age groups may not have followed the same pattern. For example, California displayed a rate in the top fifth for past month illicit drug use among persons aged 26 or older, but its rate in the 12 to 17 age group was in the middle fifth, and its rate in the 18 to 25 age group fell into the lowest fifth. On the other hand, Vermont and New Hampshire had high rates of use of any illicit drug among all three age groups (12 to 17, 18 to 25, and 26 or older) (Figures 2.1 to 2.4).
The relationship between past month use of alcohol to past year alcohol dependence or abuse was not particularly strong due in part to the widely different prevalence levels of the measures. For example, among the States with the highest rates of current alcohol use for those aged 12 or older (States ranged from 56.7 to 61.1 percent), only three States fell into the highest fifth for past year dependence on or abuse of alcohol (rates ranged from 9.1 to 10.2 percent) (Tables A.7 and A.13, Figures 3.1 and 5.1). The relationship between past month binge use of alcohol (about 23 percent nationally) and past year alcohol dependence or abuse was substantially stronger, showing 7 States in the top 10 for binge alcohol use also present in the top fifth for alcohol dependence or abuse in the past year among persons aged 12 or older (Table A.8, Figures 3.5 and 5.1).
The majority of States with high prevalence rates for alcohol dependence or abuse were not the same States that had high prevalence rates for illicit drug dependence or abuse. Only four of the States in the top fifth with the highest rates of alcohol dependence or abuse (District of Columbia, Montana, New Mexico, and Rhode Island) among persons aged 12 or older also were in the group of States with the highest levels of illicit drug dependence or abuse (Figures 5.1 and 5.9). Most of the States with the highest levels of illicit drug dependence or abuse were in the West: Arizona, Montana, Nevada, New Mexico, Oregon, and Washington. The top fifth also included the District of Columbia from the South and New York and Rhode Island from the Northeast. There were no States common in the top fifth for all three age groups (12 to 17, 18 to 25, and 26 or older) for past year illicit drug dependence or abuse (Figures 5.9 to 5.12).
There was some degree of relationship between high rates of past year illicit drug dependence or abuse and high rates of past year cocaine use at the State level. Four States were ranked among the highest for persons aged 12 or older for both measures: Arizona, District of Columbia, Nevada, and Rhode Island. However, another five States in the top fifth for past year cocaine use were ranked in the next-to-highest fifth for illicit drug dependence or abuse: Colorado, Massachusetts, North Carolina, Ohio, and Vermont (Figures 2.21 and 5.9).
Not only did geographic clustering of States occur among those with high prevalence rates, but similar clustering also was evident among the States with the lowest rates. For example, nine Southern States were in the lowest fifth for past month use of alcohol, seven Southern States were in the lowest fifth for past month binge use of alcohol, and seven Southern States were among those indicating a high risk of binge drinking (population aged 12 years or older). By contrast, only two Southern States (District of Columbia and Maryland) were in the top fifth for current use of alcohol, the District of Columbia was the only area from the South in the set of States with the highest rates of binge alcohol use, and no Southern State was in the set with the lowest rates for perceived risk of binge drinking (for persons aged 12 or older) (Figures 3.1, 3.5, and 3.9). Similarly, 10 Southern States comprised the category of States with the highest perceived risk of using marijuana occasionally, 7 Southern States displayed the lowest rates of past month marijuana use, and 8 Southern States reported the lowest rates of marijuana incidence. No Southern State was in the group of States with the lowest perceived risk of marijuana (for persons aged 12 or older) (Figures 2.5, 2.9, and 2.13).
States with the lowest rates of serious mental illness (SMI) represented an even mixture of all four regions for persons aged 18 or older: three from the Northeast, three from the South, two from the Midwest, and two from the West (Figure 6.1). The State with the lowest rate was New Jersey (6.5 percent). States in the highest fifth were somewhat more clustered geographically in the South (five States). Oklahoma had the highest rate of SMI (11.4 percent) in 2002. Five of the eight most populous States were ranked in the lowest fifth: California (7.0 percent), Texas (7.2 percent), Illinois (7.3 percent), Florida (7.6 percent), and Pennsylvania (7.7 percent). Persons aged 18 to 25 had higher rates of SMI than did the 26 or older age group. In the 18 to 25 age group, Georgia had the lowest rate (11.5 percent), and Rhode Island had the highest rate (17.5 percent) (Table A.20).
Although SMI is somewhat correlated at the individual level with past month use of an illicit drug, the correlation at the State level among persons aged 18 or older was fairly small (0.08). The correlation at the State level between SMI and past month use of cigarettes was higher, 0.36. This result is supported somewhat by research that shows a relationship between mental illness and past month use of cigarettes at the individual level (Arday et al., 1995; Kessler et al., 2003; Romans et al., 1993; Woolf et al., 1999). The correlations with dependence on or abuse of drugs or the need for treatment were generally quite low. The State-level correlation between SMI and 2000 per capita income was negative and larger (-0.51): the lower the per capita income, the higher the percentage with SMI.
Because of the unique NSDUH design and limited availability of independent data sources that provide State-level estimates, it is difficult to validate NSDUH State estimates using external sources. In the past, State estimates from this survey (i.e., the NHSDA) have been compared with estimates from the Behavioral Risk Factor Surveillance System (BRFSS) and the Youth Risk Behavior Survey (YRBS) sponsored by the Centers for Disease Control and Prevention (CDC, 2003a, 2003b). However, these CDC surveys (a) did not focus extensively on substance use, (b) employed different data collection methods, (c) did not cover all of the States on an annual basis, and (d) had varying degrees in potential response and nonresponse bias. It is, therefore, difficult to know how much confidence should be placed on comparing the results of surveys that are so different in design and implementation.
Although external validation of NHSDA and NSDUH findings is problematic, internal validation of the States can be useful. Because the State prevalence levels for 2002 are estimated in the same manner as they were for 2000 and 2001, the procedures and the results of the validation done for prior estimates apply to the 2002 estimates.5
Examining the average relative absolute bias (RAB) values from the 2000 State report that compare large sample benchmark values with small sample hierarchical Bayes estimates (see Table B.6 of the 2000 State report) for P1 obtained by fitting Model 1 (described in Section B.1 of the 2000 State report), the State model estimates (for all persons aged 12 or older) were very close to the large sample benchmark values (i.e., the bias as a percentage of the benchmark prevalence rate was very small). Specifically, the RABs for four selected outcomes were as follows:
These results suggest that, if the true value of past month use of marijuana for persons aged 12 or older in a State with a sample of about 900 persons was 5 percent, the small area estimate would, on average, fall within 0.2 percent (4.05 percent x 5 percent) of the true value. The precision of these estimates is better than that from corresponding design-based estimates of the same sample size. The PIs are about two thirds smaller, on average, than the design-based confidence intervals, but they are not as small as the PIs for the hierarchical Bayes estimates based on combining 2 years' data (as was done for the 2001 report by combining the 2000 and 2001 data).
As noted in past State reports, the models may not adequately adjust for differential nonresponse and bias effects at the State level. Any such bias resulting from nonresponse that varied in relation to the prevalence rates would raise concerns about comparisons among States.6 For such bias to exist after nonresponse adjustments have been made requires that the true probabilities for persons to respond to the survey still depend to some degree on whether they have used a substance or not.
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