5. Substance Dependence, Abuse, and Treatment

In 2000 and 2001, a National Household Survey on Drug Abuse (NHSDA) respondent was defined as needing treatment if he or she met the criteria for dependence or abuse or received treatment at a specialty facility in the past year. The questions to measure dependence or abuse status are based on the criteria specified in the 4^th edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (American Psychiatric Association [APA], 1994). Because of the changes between 1999 and 2000–2001 in the questions and definitions employed for determining dependence, abuse, and treatment need, it is not appropriate to compare the estimates in this report with estimates from 1999 or earlier. As with most other measures in this report, the NHSDA data from 2000 and 2001 have been combined to produce better estimates than are possible with just a single year's data. Because the 1999 data were based on different definitions, it is not possible to estimate a trend between 1999–2000 and 2000–2001.

An estimated 16.6 million Americans age 12 or older in 2001 were classified with dependence on or abuse of either alcohol or illicit drugs, a figure significantly higher than in 2000—about 14.5 million (Epstein, 2002; Office of Applied Studies [OAS], 2002c). Most of these persons (11.0 million) were dependent on or abused alcohol only. Another 2.4 million were dependent on or abused both alcohol and illicit drugs, while 3.2 million were dependent on or abused illicit drugs but not alcohol. Because these counts often translate into very low rates of dependence or abuse in the population, the rates and counts are associated with relatively large prediction intervals (PIs). For example, the State with one of the highest percentages of dependence on or abuse of illicit drugs (age 12 or older) was Nevada with 2.9 percent. However, the 95 percent PI is from 2.2 to 3.8 percent, and the lower limit falls more than halfway into the third quintile. Therefore, one should exercise caution in making decisions based solely on one of the dependence or abuse measures.

5.1. Alcohol Dependence or Abuse

Nationally, 5.9 percent of the population age 12 or older was classified with dependence on or abuse of alcohol in the past year (Epstein, 2002; OAS, 2002c). Persons age 18 to 25 had the highest rates of alcohol dependence or abuse (14.8 percent).

State estimates for 2000–2001 for persons age 12 or older ranged from 4.2 percent in North Carolina to 8.5 percent in North Dakota (Figure 5.1; Table B.13). States in the highest fifth tended to be mostly Western (Montana, New Mexico, Alaska, and Colorado) or Midwestern (North Dakota, Nebraska, and South Dakota). States in the lowest fifth were mostly in the South (North Carolina, South Carolina, Virginia, Georgia, Alabama, and Kentucky).

In the 12 to 17 age group, the estimated percentage of those identified as having an alcohol abuse or dependence problem ranged from 3.6 percent in Georgia to 9.7 percent in Montana (Figure 5.2; Table B.13). Among persons age 18 to 25, the lowest percentage was found in North Carolina (10.5 percent), and the highest State percentage was in North Dakota (24.2 percent) (Figure 5.3; Table B.13). Four States were in the highest fifth for the 12 to 17, 18 to 25, and 26 or older age groups: North Dakota, Montana, Massachusetts, and Nebraska.

In 2001, the percentage of persons estimated to be dependent on alcohol in the past year was only about 40 percent of those who were determined to be dependent on or abusing alcohol in the past year. State estimates for alcohol dependence in 2000–2001 for persons age 12 or older fell into a narrow range from 2.1 percent in New Jersey to 3.4 percent in the District of Columbia (Figure 5.5; Table B.14). Only four of the States in the top fifth for dependence or abuse also could be found in the top fifth for just dependence: District of Columbia, New Mexico, South Dakota, and Alaska. A number of States that were not in the top fifth for alcohol dependence or abuse were in the top fifth for alcohol dependence: Louisiana, Mississippi, Oklahoma, California, Illinois, and Oregon. The highest rates for alcohol dependence occurred in the 18 to 25 age group, with Montana having the highest rate—7.9 percent (Figure 5.7; Table B.14).

5.2. Illicit Drug Dependence or Abuse

Nationally, in 2001 about 2.5 percent of persons age 12 or older were dependent on or had abused illicit drugs in the past year, close to half of the percentage of those who were dependent on or had abused alcohol (5.9 percent) (OAS, 2002c).

States with estimated rates in the highest fifth were mostly either in the West (Nevada, California, Washington, New Mexico, Colorado, and Oregon) or in the Northeast (Massachusetts, Connecticut, and Vermont) (Figure 5.9; Table B.15). Only three of the States in the highest fifth for past year illicit drug dependence or abuse also were in the top fifth for past year alcohol dependence or abuse: Massachusetts, New Mexico, and Colorado (Figures 5.1 and 5.9; Table s B.13 and B.15).

Rates were slightly higher in the 12 to 17 and 18 to 25 age groups than other age groups. For States in the top fifth for dependence on or abuse of illicit drugs in the past year among youths age 12 to 17, the rates ranged from 5.7 to 7.3 percent (Figure 5.10; Table B.15). For States in the top fifth for dependence on or abuse of illicit drugs among those age 18 to 25, the rates ranged from 7.2 to 8.4 percent (Figure 5.11; Table B.15). Three States were in the top fifth for three age groups (18 to 25, 26 or older, and 12 or older): Nevada, Connecticut, and Vermont.

The percentage of persons estimated to be dependent on illicit drugs in the past year was about 64 percent of those who were estimated to be dependent on or abused illicit drugs in the past year. State estimates for illicit drug dependence for persons age 12 or older ranged from 0.9 percent in North Dakota to 2.1 percent in California (Figure 5.13; Table B.16). The highest rates of illicit drug dependence were among persons age 18 to 25, with the highest rate in Vermont—6.3 percent (Figure 5.15; Table B.16).

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 for persons age 12 or older at the State level. Six States were ranked among the highest for both measures: Nevada, California, Massachusetts, Vermont, New Mexico, and Colorado (Figures 2.20 and 5.9; Table s B.6 and B.15).

5.3. Alcohol or Illicit Drug Dependence or Abuse

The national rate for past year dependence on or abuse of alcohol or illicit drugs among persons age 12 or older was about 7.3 percent, slightly higher than the rate for just alcohol dependence or abuse (5.9 percent) and less than 3 times larger than the rate for illicit drug dependence or abuse (2.5 percent) (OAS, 2002c).

When examining dependence on or abuse of alcohol or illicit drugs at the State level, the States with high rates for alcohol tended to dominate the top fifth for alcohol and illicit drugs combined because of the higher rates of dependence on and abuse of alcohol relative to illicit drugs (Figures 5.1, 5.9, and 5.17; Table s B.13, B.15, and B.17).

For those age 12 or older, the State percentages ranged from a low of 5.2 percent in North Carolina to a high of 9.3 percent in North Dakota for past year dependence on or abuse of illicit drugs or alcohol (Figure 5.17; Table B.17). Six out of ten States in the top fifth for dependence on or abuse of illicit drugs or alcohol also were in the top fifth for dependence on or abuse of alcohol alone.

The prevalence rate among persons age 18 to 25 was almost 3 times as high as that for all persons age 12 or older (Figures 5.17 and 5.19; Table B.17). North Dakota's rate of 27.1 percent was the highest among States for this age group. Many of the States in the top fifth both for ages 18 to 25 and for ages 12 to 17 were the same as those in the top fifth for all persons age 12 or older (Figures 5.17 to 5.19; Table B.17).

5.4. Illicit Drug Treatment Gap

The definition of a person needing treatment is that he or she meets the criteria for abuse of or dependence on illicit drugs according to the DSM-IV criteria or has received treatment in the past year. The illicit drug treatment gap is defined as the number of persons who needed treatment for use of illicit drugs but did not receive treatment in a specialty substance abuse treatment facility in the past year. It is important to note that the treatment gap was not calculated here by estimating one model for treatment need and another model for receipt of treatment, and then subtracting one from the other at the State level. The reason for this is that the percentage of persons receiving treatment is too small to estimate well. Instead, at the individual level, persons are designated as being in the treatment gap based on meeting the criteria for treatment need and whether they received treatment for abuse of, or dependence on, illicit drugs in the past year. In general, the definitions of dependence, abuse, or treatment for alcohol or illicit drugs contain components that often overlap one another, and a researcher may be tempted to subtract them at the State level to obtain some missing component. Each measure is based on a different model, and subtraction can lead to erroneous results, such as a "negative" component.

Given 2 years' data (2000–2001), the State estimates of the percentage treatment gap permit the sample State data to have a greater influence on the result than by using data only for the year 2000, especially for the States with small yearly samples of approximately 900 persons. This approach results in a wider range between the lowest and the highest rates for 2000–2001 (from 1.35 to 2.68 percent) compared with the range based on 2000 data alone (from 1.37 to 2.29 percent).

California had the highest percentage treatment gap in 2000–2001 at 2.7 percent of all persons age 12 or older (Figure 5.21; Table B.18). The other States in the top fifth were mainly in the West (Nevada, Colorado, and Washington) or in the Northeast (Massachusetts, Vermont, and Maine). California also had the largest number of persons age 12 or older in the treatment gap, approximately 708,000, or 15.6 percent of the total for the Nation.

Almost 60 percent of the total number of persons needing but not receiving treatment was in the age group from 12 to 25. However, that group accounts for only 23 percent of the total population age 12 or older. The percentage of the total treatment gap accounted for by persons age 12 to 25 at the State level ranged from 50 percent in the District of Columbia to 72 percent in Idaho.

The overall treatment gap increased from 1.7 percent in 2000 to 2.2 percent in 2001, a relative increase of 29 percent (OAS, 2002c). Although one cannot say very much about individual State changes in the treatment gap between 2000 and 2001 given the relatively small yearly sample sizes, it is useful to look at more general conclusions given the significant policy interest in this area. Because the State estimates for 2000–2001 combine the estimates across the 2 years, on average the increase in State estimates is from 1.7 to 1.95 percent [(1.7 percent + 2.2 percent) / 2], dampening the size of the true national change. The manner in which the estimates are calculated based on 2 years' data (2000–2001) leads to only half of the (true) 0.5 percent increase in the percentage treatment gap between 2000 and 2001.

Even with only half of the national increase, the State estimates for 2000–2001 are such that 42 of the 51 States and the District of Columbia had increases from their corresponding estimates for 2000 (based on the single year of data). Most of these individual State increases are not statistically significant because the percentage increases are so small. On average, however, the States comprising the lowest two quintiles in 2000 (the first and second quintiles) showed average increases that were less than the national average (0.10 and 0.16 percent, respectively, vs. 0.25 percent for the national average). In the lowest fifth, about half of the States had "increases" while the others had "decreases." In the middle fifth (the third quintile), the estimated average increase was 0.24 percent (almost identical to the "national" increase of 0.25 percent), and all States in that group had higher estimates for 2000–2001 than for 2000.

The largest percentage increase in the treatment gap was among States in the next-to-highest fifth (fourth quintile) where the average increase was 0.39 percent; all States in that group had higher estimates in 2000–2001 than in 2000. In the top fifth, 8 out of 10 States had higher estimates in 2000–2001. The average increase was only 0.23 percent, due partly to the effect of the national model that generally acts to shrink the direct sample-based State estimates that are higher than the national average back toward the estimate based on the national model. This effect of the model on the 2000–2001 State estimates is really quite small. The average difference in the top fifth between the average of the hierarchical Bayes estimates (2.31 percent) and the design-based estimate, the simple-weighted average across the 2 years (2.44 percent), was -0.13 percent, which was only about 5 percent lower in a relative sense than the average percentage estimate for that group.

Therefore, along with the national increase in the percentage treatment gap between 2000 and 2001, it can be inferred that most States shared in that increase. That is, States in the two lowest fifths in 2000 had increases that were on average lower than the national average, States in the middle fifth had increases that were similar to the national average increase, and most States in the highest two fifths displayed increases that were greater than the national average.

Figure 5.1 Percentages Reporting Past Year Alcohol Dependence or Abuse among Persons Aged 12 or Older, by State: 2000 and 2001

Figure 5.1 D