1998 National Household Survey on Drug Abuse:  Population Estimates

FORMAT AND ORGANIZATION OF THE POPULATION ESTIMATES TABLES

NHSDA drug use prevalence data are presented for each gender; four major age groups (12 to 17, 18 to 25, 26 to 34, and 35 years old or older); three major mutually exclusive racial/ethnic groups, based on respondents' self-classifications (Hispanic in origin, regardless of race; white, not of Hispanic origin; and black, not of Hispanic origin); and four geographic regions. (Those who did not identify themselves as Hispanic, white, or black are included in the population totals, but separate estimates are not presented for this "other" category because the sample size is too small [see Table 1B].) Tables are presented separately for the total population, whites, Hispanics, blacks, and geographic region. The four U.S. Bureau of the Census regions are Northeast, North Central, South, and West (see Exhibit 1). For each drug, eight tables are arranged to facilitate group comparisons. Data for the estimated numbers of users in subgroups are arranged in rows and presented by gender for each of four age groups. Data in the remaining seven tables for each racial/ethnic or regional subgroup are presented first by age, then by gender, and finally for the total population.

Time periods of use shown in column headings are "ever used," "used past year," and "used past month." These categories are cumulative (i.e., those who have "used [in the] past month" also are included in the "used [in the] past year" and "ever used" categories). Likewise, those who have "used [in the] past year" are included in the "ever used" estimates.

Other than presenting results by age group and other basic demographic characteristics, no attempt is made in this report to control for potentially confounding factors that might help explain any associations observed. This point is particularly salient with respect to race/ethnicity, which tends to be highly associated with socioeconomic characteristics. Also, the cross-sectional nature of the data precludes any causal interpretations of observed relationships. Nevertheless, data presented in this report are useful for comparing demographic subgroups with respect to drug use rates, regardless of why they differ.

Prevalence Estimates for Specific Drugs and Drug Classes

Section III presents the basic set of drug use prevalence estimates grouped by various drug categories. The first drug category presented is "Any Illicit Drug," which includes any use of marijuana/hashish; cocaine, including crack; inhalants; hallucinogens, including lysergic acid diethylamide (LSD) and phencyclidine (PCP); heroin; and the nonmedical use of psychotherapeutics (i.e., stimulants, sedatives, tranquilizers, and analgesics). Following the estimates for any illicit use, tables are presented separately for various specific categories of illicit drug use, as well as for alcohol, cigarettes, and smokeless tobacco. The small number of respondents reporting these drug use behaviors resulted in low precision for most "used past month" estimates, as well as many other estimates; therefore, less detail is shown for estimates of PCP use, LSD use, heroin use, and needle use (see Tables 16 to 19).

Frequency of Drug Use Among Past Year Users

Data presented in Section IV are useful for identifying how often a drug is used. After results from earlier surveys were published, the estimate of those who had used a drug in the past month was cited by some readers as an estimate of the number of "regular users." This interpretation was unsatisfactory because past month users include both those experimenting with the drug as well as regular users. Therefore, information has since been collected on the frequency of drug use in the past year.

Frequency of drug use during the past 12 months is classified into three categories: "at least once," "12 or more days," and "51 or more days." The categories are cumulative; those using "51 or more days" also are counted among the "12 or more days" and the "at least once" users. Similarly, those using "12 or more days" also are counted among those who have used "at least once" in the past year. By definition, estimates for those who have used "at least once" are equivalent to those who have "used past year" in earlier tables.