Measurement of adolescent drug use.

There is widespread agreement that estimates of adolescent drug use prevalence from the National Household Survey of Drug Abuse (NHSDA) and Monitoring the Future (MTF) are subject to considerable measurement error. Nevertheless, some have suggested that trends over time in these prevalence estimates probably reflect true trends in drug use, since underreporting may be assumed to be constant over time. A recent National Research Council report criticizes this assumption on logical grounds. The present study examines adolescent drug use responses on the NHSDA and MTF for evidence of "drug omission," "jargon confusion" and "conceptual confusion," three types of misreporting expected to vary in magnitude with changes in drug use practices and changes in survey items. Results demonstrate that adolescent drug users are significantly more likely than adults to report use of drugs not listed in the NHSDA. Among adolescents who wrote in the "other" drugs they used, 66% and 86% of hallucinogen and inhalant responses showed confusion over the meaning of the pharmacological terms used in the NHSDA. Almost 20% of MTF respondents who report lifetime use of Rohypnol or ecstasy, when specifically queried about these drugs, deny lifetime use of any substances in the drug classes intended to assess use of Rohypnol and ecstasy. MTF respondents reporting lifetime use of PCP underreport use of hallucinogens at rates that vary substantially over time, from a high of 45% (in 1986), to a low of just 8% (in 1998). The implications of these findings for adolescent drug use prevalence estimation and survey design are discussed.