Understanding the differences in youth drug prevalence rates produced by the MTF, NHSDA, and YRBS studies

This paper explores potential reasons for the differences in drug use prevalence rates among youth generated by three nationally representative surveys: The National Household Survey on Drug Abuse (NHSDA), the Monitoring the Future (MTF) survey, and the Youth Risk Behavioral Survey (YRBS). The MTF and YRBS are the most similar of the surveys, being conducted among students in a classroom using self-administered questionnaires. The NHSDA is conducted in the respondent's household, but it has always used self-administered procedures for the drug questions. Nevertheless, the NHSDA generally reports the lowest drug prevalence rates for youth among the three surveys. There are a number of methodological differences across the surveys that cumulatively, probably account for the differences in estimates. Some of the differences appear to be due to telescoping, in that when a calendar was introduced to anchor past 30 day and 12 month time periods in the NHSDA, prevalence rates for illicit drugs were reduced. However, there is substantial similarity in the trends over time among the three surveys, especially for cigarettes, alcohol and cocaine. Many of the estimates generated by the three surveys have overlapping confidence intervals, which suggests the estimates are not statistically significantly different from one another.