be affected by the data collection methodology. Surveys that can effectively ensure confidentiality and anonymity and that are conducted in noncoerced settings will tend to have relatively low misreporting rates.

Without knowledge of the fraction of respondents who misreport their drug use, it is not possible to identify either prevalence levels or trends. Johnston et al. (1998) argue that invalid reporting rates in the national surveys are low and vary little from year to year so that the data can be used to infer trends. Pepper discusses some potentially plausible assumptions about incorrect response that make it possible to bound prevalence level (Appendix D). It is not known, however, whether either Johnston’s or Pepper’s assumptions are correct.

Concerns about inaccurate response in the NHSDA and MTF are not new. In fact, in a new effort to learn more about the validity of self-reports, SAMHSA is undertaking a project that works with a subsample of about 2,000 people from the 1999 NHSDA panel. The study will administer the questionnaire following normal procedures, then will hold de-briefing sessions in which respondents will be encouraged to give true answers to the questions, on the grounds that the results are important because policy will be based on them. Respondents will then be offered $25 for a urine sample and $25 for a hair sample. This effort went into the field in September 1999. The sample is limited to those ages 12 to 25, the age group that has the highest rates of drug use. Data collection will continue for one year. The questions cover use of tobacco, marijuana, opiates, and amphetamines. The committee is encouraged by the recent initiation of a project to evaluate inaccurate response in the NHSDA, but this project should be considered as only the first step.

Without consistent and reliable information on inaccurate response in the national surveys, researchers will be forced to make unsubstantiated assumptions about the validity of responses. Thus, the committee strongly recommends a systematic and rigorous research program (1) to understand and monitor inaccurate response in the national use surveys and (2) to develop methods to reduce reporting errors to the extent possible.


The U.S. government, in partnership with the individual states, has created a remarkable source of surveillance information that provides timely early warning about infectious disease outbreaks in essentially all local area jurisdictions, and the spread of epidemics across the nation. On occasion, this surveillance network also has functioned quite well to detect and to disrupt epidemics of noninfectious origin, but not for such drugs as cocaine, crack, MDMA (“ecstasy”), or other illegal drugs.

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