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Computer Assisted Interviewing for SAMHSA's National Household Survey on Drug Abuse |
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Since 1971, the NHSDA has provided information on the extent of substance use and abuse in the United States. The first survey was conducted by the National Commission on Marihuana and Drug Abuse and established the basic methodology of using in-person interviews combined with self-administered answer sheets to increase the respondents' privacy and their willingness to respond. The self-administered answer sheets were also designed to avoid the use of skip patterns (i.e., contingent questioning structures used in computer-administered questionnaires in recent NHSDAs) so that interviewers would not be able to infer drug use on the part of the respondent based on the time it took to complete the answer sheets. In addition, the basic sampling strategy of targeting the survey toward younger people in order to improve the precision of the estimates was established in this first survey (Gfroerer, 1992).
From 1971 through 1998, 17 rounds of the NHSDA were conducted.3 The survey became an annual, widely followed national benchmark beginning in 1990. The sample sizes increased over the years to provide accurate estimates of trends among minorities, youths, and other groups especially affected by drug abuse. From 1991 to 1993, supplemental samples were selected for six large metropolitan areas: Chicago, Denver, Los Angeles, Miami, New York City, and Washington, DC. Periodically, rural supplements were selected. Emerging issues, such as successful ballot initiatives in November 1996 to legalize medical uses of marijuana in California and Arizona, led to increases in sample sizes in these States in April 1997.
The core content includes questions on alcohol, tobacco, marijuana and hashish, cocaine, heroin, hallucinogens, inhalants, and the nonmedical use of prescription drugs. Prior to 1994, there were changes in both the number and wording of questions that addressed this content. To provide a more constant set of core questions, a new set of core answer sheets was adopted in 1994. The core answer sheets include (a) tobacco, (b) alcohol, (c) marijuana, (d) cocaine in any form, (e) crack cocaine, (f) heroin, (g) hallucinogens, (h) inhalants, and nonmedical use of (i) analgesics, (j) tranquilizers, (k) stimulants, and (l) sedatives. This revised core included fewer basic questions, revisions of wording so that questions were asked consistently across these answer sheets, rewording to enhance understanding, and a fixed order of administration. More information on changes that were made in 1994 can be found in SAMHSA (1996a). The core questions include age at first use, lifetime use, past year use, and past month use. In addition to the core, other topics have been covered on a periodic basis, and the substantive content has broadened over time. Topics have included mental health, need for drug treatment, perceptions of risk, driving behaviors, human immunodeficiency virus (HIV) risk behaviors, and others. These changes in content and scope have been made to meet the needs of researchers and policymakers for authoritative and timely information and analysis.
There has also been a continual focus on evaluating and improving the methodology of the survey by focusing on content, sample design, questioning strategies, editing methods, and estimation procedures. Methodological improvements (Gfroerer, 1992; SAMHSA, 1996a) have included a variety of efforts:
an extensive review of the methodology by an NHSDA advisory committee in 1984 and a subsequent revision of the questioning methods for the 1985 survey;
a small-scale double-blind validation study in 1986 in which a sample of people from drug treatment facilities were interviewed using the NHSDA methodology (Harrell, 1985, 1997);
the adoption of machine editing in 1988 to provide detailed documentation of editing and improve the consistency of edits;4
increases in sample sizes and improvements in the sampling methodology;
a series of methodology studies that included a cognitive appraisal of the 1988 instrument (Forsyth, Lessler, & Hubbard, 1992), a study of missing and inconsistent data and nonresponse in the 1988 survey (Cox, Witt, Traccarella, & Perez-Michael, 1992; Witt, Pantula, Folsom, & Cox, 1992), a series of laboratory studies examining questioning techniques (Hubbard, 1992), a nonresponse follow-up study (Caspar, 1992), an experimental field test of alternative questionnaires conducted in 1990 (Hubbard, Pantula, & Lessler, 1992; Turner, Lessler, & Devore, 1992a; Turner, Lessler, George, Hubbard, & Witt, 1992b; Turner, Lessler, & Gfroerer, 1992c), and a U.S. Bureau of the Census match study that examined correlates of household screening nonresponse and person-level nonresponse (Gfroerer, Lessler, & Parsley, 1997a; Parsley, 1993);
an evaluation of the feasibility of using a telephone survey to collect drug use data (Gfroerer & Hughes, 1991, 1992);
a 1992 experiment examining the use of answer sheets with skip patterns (Lessler & Durante, 1992); and
pretests of revised questionnaires in 1992 and 1993 in preparation of the adoption of the revised questioning and editing strategies in 1994 (SAMHSA, 1996a).
In addition to the methodology studies that have been conducted in the context of the NHSDA, the measurement methodology for the survey has been evaluated by comparing it to results from other studies. For example, Gfroerer, Wright, and Kopstein (1997b) compared the NHSDA to Monitoring the Future (MTF), which is a school-based survey that produces estimates of drug use by adolescents for many of the same substances as the NHSDA. The two surveys show similar trends, but the rates of drug use are higher in the MTF. Although many methodological differences were noted between the two surveys, the authors speculated that the higher rates of use in the MTF may be due to greater underreporting in the household setting used in the NHSDA.
Other studies have examined the impact that the mode of interview and the privacy of the interview setting had on drug use reporting. For example, Gfroerer and Hughes (1991, 1992) compared estimates from the NHSDA to those from a random-digit dialing (RDD) survey, and Aquilino (1994) compared three modes of interviewing for a group of respondents who were randomly assigned to complete either a telephone interview, a personal interview, or a self-administered questionnaire during a personal interview. Using data from the same experiment, Aquilino (1997) examined the effect of the presence of third parties on the reporting of illicit drug use. The results from the majority of these studies have supported the use of the basic methodology of the NHSDA. Household interviews, self-administered questionnaires, and a private setting all contributed to improved reporting.
In spite of the evidence supporting the basic methodology, comparisons with other surveys of drug use (Gfroerer et al., 1997b) indicated that improvements could be made. The advent of computer-assisted interviewing (CAI) procedures, particularly audio computer-assisted self-interviewing (ACASI), clearly offered an opportunity for enhancing the privacy of the interviews and improving the measurement methods. In reviewing the results of the 1990 NHSDA field experiment, Turner et al. (1992a) noted that although the research supported the use of self-administered questionnaires (SAQs), it does pose problems for respondents with poor reading skills. Respondents who cannot read well enough to complete the questionnaire on their own must depend on the interviewer to read the questions and answers to them while they mark their answers on answer sheets. Clearly, the interviewing environment is not as private for these respondents as it is for those who can read well, and ACASI permits them to answer in complete privacy. Numerous other studies had demonstrated that computer-assisted personal interviewing (CAPI) improves the quality of survey data and that ACASI results in increased reporting of sensitive behaviors (see Chapter 3). However, as discussed in Chapter 3, moving the NHSDA to use CAI procedures entailed examining and evaluating a number of issues.
3 The National Institute on Drug Abuse (NIDA) sponsored the NHSDA from 1974 to 1991; the survey series has been sponsored by the Substance Abuse and Mental Health Services Administration (SAMHSA) since October 1992.
4 One of the key privacy-enhancing features of the NHSDA was that each answer sheet was placed in an envelope after its completion. At the end of the entire interview, this envelope was then sealed and returned for processing. Thus, there was no field editing of the respondent-completed answer sheets; moreover, because of the promises of confidentiality and anonymity, respondents were not called back to resolve inconsistencies.
 This page was last updated on September 27, 2006. |
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SAMHSA, an agency in the Department of Health and Human Services, is the Federal Government's lead agency for improving the quality and availability of substance abuse prevention, addiction treatment, and mental health services in the United States. 
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