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Prevalence of Substance Use Among Racial & Ethnic Subgroups in the U.S.

2.1 Measurement of Substance Use, Dependence, and Need for Treatment

Each NHSDA interview takes about one hour to complete and incorporates procedures designed to maximize honest reporting of substance use. Respondents aged 12 to 17 are allowed to participate in the survey only after the interviewer has received parental permission. In each of the 1991, 1992, and 1993 surveys, more than 40 percent of the adolescent interviews were conducted in complete privacy, with only the interviewer and respondent present, while less than 20 percent were conducted with at least one other person constantly present. (For details, see SAMHSA, 1993, Table B.10; SAMHSA, 1995b, Table B.10; and SAMHSA, 1995c, Table B.10.) 

Self-administered answer sheets are used by respondents for all alcohol and illicit drug use questions, so that responses are not revealed to interviewers or to any other persons who may have been present at the interview. [ Exceptions to the use of self-administered answer sheets are the questions about tobacco use. In 1991-1993, these questions were interviewer-administered. This procedure was revised in the 1994 NHSDA so that youths now respond using self-administered answer sheets. Results indicate that estimates of youth tobacco prevalence prior to 1994, such as those in this report, are substantial underestimates.] Respondents are given a guarantee of confidentiality and told that only persons connected with the research will ever see their answers. After the questionnaire is completed, the answer sheets are placed in an envelope that is then sealed and mailed back to the data collection contractor with no name or address information included.

The analyses in this report are based on NHSDA variables that are derived from questionnaire items on substances used in the past year and problems associated with use. The following NHSDA questionnaire items, called "recency" items, were used to determine past-year drug use:

1) Cigarettes: "When was the most recent time you smoked a cigarette?"

2) Alcohol: "When was the most recent time you had an alcoholic drink, that is, beer, wine, or liquor or a mixed alcoholic drink?"

3) Marijuana: "When was the most recent time you used marijuana or hash?"

4) Cocaine: "When was the most recent time you used cocaine, in any form?"

5) Illicit drugs other than marijuana or cocaine: "When was the most recent time you used [name of drug]?"

Respondents who reported that their most recent use of the specified substance occurred within the twelve-month period preceding the interview were classified as having used the substance during the past year. The recency question varies depending on the type of substance. For example, when asking about sedatives, tranquilizers, stimulants, and analgesics, the question limits use to "nonmedical use." These forms of drug use make up the illicit drugs along with marijuana, cocaine (including crack), inhalants, hallucinogens, and heroin. In other words, any use of any of these drugs in the past year is identified as use of illicit drugs.

To measure heavy past-month alcohol use, we used responses to the following question:

6) Heavy past-month alcohol use: "On about how many days did you have five or more drinks of beer, wine, or liquor on the same occasion during the past 30 days?"

Individuals who responded five or more days were classified as heavy past-month alcohol users.

To measure heavy past-month cigarette use, we used responses to the following question:

7) Heavy past-month cigarette use: "How many cigarettes have you smoked per day, on the average, during the past 30 days?"

Individuals who responded "about a pack a day (16-25 cigarettes)" or more than a pack a day were classified as heavy past-month cigarette smokers.

We also want to identify patterns of problem substance use. Therefore, two kinds of general indicators of problem use were developed, based on responses to questions about drug problems: a measure of dependence on alcohol and a measure of need for illicit drug abuse treatment. First, each type of substance use identified above has a corresponding dependence indicator that is created from respondents' self-reports of behavioral consequences and dependence symptoms they may have experienced as a result of using the substance during the twelve months preceding the interview. Respondents were asked to identify specific substances that caused them to experience each of seven consequences/symptoms during the year preceding the interview. (The questions were based on questionnaire items and diagnostic criteria presented in the Diagnostic and Statistical Manual of Mental Disorders, Third Edition [DSM-III-R; American Psychiatric Association, 1987].) 

The seven consequences/symptoms were: 1) feeling depressed or losing interest, 2) getting involved in arguments or fights, 3) feeling alone or isolated, 4) feeling nervous or anxious, 5) developing health problems, 6) experiencing difficulty in thinking clearly, and 7) feeling irritable or upset. For each substance, we used the respondents' reports of these seven consequences/symptoms, together with their reports of the most recent time the substance was used, and of their experiences of "trying to cut down" and using more of the substance "to get the same effect," to define five "criteria" of dependence.

A. The substance caused one or more of the seven consequences/symptoms, and the substance was last used during the past month.

B. The substance caused the respondent to get less work done during the past year, and the respondent last used the substance during the past year.

C. The respondent was unable to reduce his or her use of the substance ("cut down") during the past year.

D. The respondent needed more of the substance to get the same effect during the past year.

E. The respondent felt sick when he or she tried to cut down during the past year.

We classified respondents as "dependent on alcohol" during the past year if two or more of the five criteria of dependence were satisfied for alcohol.

Second, following Epstein and Gfroerer (1996), we constructed a measure of the need for illicit drug abuse treatment. A respondent was classified as in need of illicit drug abuse treatment if he or she 1) was dependent on an illicit drug during the past year, 2) reported injection substance use or heroin use during the past year, 3) used sedatives, stimulants, tranquilizers, analgesics nonmedically, inhalants, hallucinogens, or cocaine weekly during the past year, or 4) received treatment for illicit drug use during the past year.

Table 2.1 presents the estimated number and percentage of total persons, and males and females aged 12 and older, who were classified as positive according to this measure. This information is presented for each of the nine measures of substance use, alcohol dependence, or need for treatment, which are defined in this section and analyzed in Chapters 3, 4, and 5. For example, we estimate that there were about 63.4 million persons who used cigarettes in the year preceding the survey, about 31 percent of the NHSDA target population aged 12 and older. Of the 63.4 million past-year cigarette users, 33.1 million were male, accounting for about 34% of the male population aged 12 and older, and 30.3 million were female, accounting for about 28% of the female population aged 12 and older. Standard errors for Table 2.1, and subsequent tables in this report, are presented in the Appendix.

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This page was last updated on May 19, 2008.