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Informing America’s Policy on Illegal Drugs: What We Don’t Know Keeps Hurting Us
drug-related episodes at emergency rooms and within the coroner’s jurisdiction. These “event-based” surveys have been used for operational purposes in the criminal justice and public health systems. They also are capable of providing evidence on emerging problems in high-risk populations.
In this section we describe each of the four surveys, none of which provides information on drug consumption; we go on to recommend study of the feasibility of obtaining such information. Next we discuss issues of population coverage and sample size in the four surveys. We then investigate how nonresponse and inaccurate response may affect measurement of levels and trends in drug use.
Description of the Surveys
The four primary surveys used to monitor drug use in the United States collect information on whether the respondent used a wide range of illegal drugs (see Table 3.1). Specific questions are asked about alcohol, tobacco, marijuana, cocaine, hallucinogens, heroin, inhalants, and nonmedical use of psychotherapeutics. The surveys also include various levels of detail on the respondent’s demographics, health status, insurance, drug treatments, illegal activities, perceptions, and geographic location.
The National Household Survey of Drug Abuse (NHSDA) is a multistage probability sample providing annual self-report estimates of the number of drug users, their pattern of use, and their characteristics. The survey covers the U.S. civilian population age 12 and older. About 2 percent of the population is not covered, including persons who are in the military, in jail, in a long-term residential treatment regimen, and those who are homeless but not in shelters.
The National Commission on Marihuana and Drug Abuse conducted the first survey in 1972–1973. The National Institute on Drug Abuse (NIDA) then conducted surveys approximately every 2 to 3 years from 1973 to 1991. Since 1992, the Substance Abuse and Mental Health Service Administration (SAMHSA) has conducted the survey annually. Over the years, the sample size has been increased from 9,000 in 1988 to 26,000 in 1998 and 70,000 in 1999. The sample is now sufficiently large to enable estimation of the prevalence of illegal drug use in each of the 50 states. The sampling scheme is also stratified to ensure adequate representation by age, race, and ethnic background.
The instrument includes questions about the drug use of the respondent. For each drug and for combinations of drugs, the survey elicits information on the frequency of use within the respondent’s lifetime, past year, and past 30 days. Respondents are asked the age when they were first exposed to and first used each drug, as well as when they last used it.