tics on trends in drug use in the general population:2 the National Household Survey on Drug Abuse (NHSDA) and the Monitoring the Future study (MTF). Additionally, a number of surveys and other data collection efforts describe use and abuse in specific populations (Table 4.1). Other major accomplishments of epidemiological research include the development of valid measures and survey methodologies and the collection and analysis of data on co-occurring psychiatric disorders, natural history, and etiology of drug abuse.

General Population Surveys

National Household Survey on Drug Abuse

NHSDA has been conducted periodically since 1971 and is currently an annual survey.3 It provides national-level estimates of the prevalence of use of illicit drugs, alcohol, and tobacco among members of the household population of the United States (surveys before 1991 excluded Alaska and Hawaii). The survey is estimated to represent 98 percent of the total population age 12 and over; completion rates of the survey in recent years vary between 74 and 84 percent. The subpopulations excluded are homeless persons; persons living in correctional facilities, nursing homes, and treatment centers; and active military personnel (SAMHSA, 1995c).

The NHSDA series was designed to measure the prevalence and correlates of alcohol, tobacco, and illicit drug use in the United States; sufficient continuity has been evident in the core questions of NHSDA to be able to chart trends in drug use since 1972. In each survey, similar questions have been asked about the use of illicit drugs, alcohol, and tobacco in the respondent's lifetime, in the past year, and in the past month. Illicit drug use is defined as use of illegal drugs and nonmedical use of prescription-type psychotherapeutic drugs.

An important aspect of the epidemiology of drug use is the variation among persons (based on gender, age, and other demographic factors), place (region, population density), and time. Table 4.2 shows the prevalence of illicit drug use in the past month among the household popula-


It is important to note that the total number of users results from the rates of use in different age groups in the population and from the demographic structure of the population. The actual number of users may increase while the average or overall rate of use are declining.


The survey has been conducted annually since 1990. The National Commission on Marihuana and Drug Abuse sponsored the 1971 and 1972 surveys, NIDA sponsored the NHSDA from 1974 to 1990, and the Substance Abuse and Mental Health Services Administration has been the responsible agency since 1992.

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