Diminished Lifetime Substance Use Over Time: An Inquiry Into Differential Underreporting

This study investigates underreporting of lifetime marijuana and cocaine use in the National Longitudinal Survey of Youth. Comparing responses provided in 1988 with responses provided in 1984, this study evaluates the prevalence and correlates of two indicators of underreporting, including use denial and use reduction. At follow-up in 1988, a high rate of underreporting was evident for both marijuana and cocaine, with rates of use reduction observed for just under one-third of all 1984 marijuana users and just over one-third of all 1984 cocaine users. Outright denial of use in 1988 was almost twice as prevalent among cocaine users as it was among marijuana users; nearly 19 percent of all cocaine users denied use at follow-up, compared with nearly 12 percent of all marijuana users. Correlates of under reporting varied by substance and by measure of underreporting. The most consistent correlates of underreporting were interview mode, race/ethnicity, and educational status. Those interviewed by telephone, minority respondents, and those with lower levels of education were more likely to underreport. Race/ethnicity ef fects were particularly striking in our analyses. Black respon dents had at least twice the odds of underreporting compared with white/other respondents for every indicator of underreporting. Findings are compared with other recent research on underreporting and are discussed in the context of recent substance use prevalence findings.