Trends and correlates of discordant reporting of drug use among nightclub/festival attendees, 2019–2022

People who attend nightclubs and festivals are known for high prevalence of party drug use, but more research is needed on underreporting in this population, in part because unintentional drug exposure through adulterated drug products is common. We examined the prevalence of drug use in this population, based both on self-reporting and on hair test results, with a focus on the detection of underreported use. Adults entering nightclubs and festivals in New York City were asked about past-year drug use in 2019–2022 (n = 1,953), with 328 providing an analyzable hair sample for testing. We compared trends in self-reported drug use, drug positivity, and "corrected" prevalence, adjusting for unreported use, and delineated correlates of testing positive for ketamine and cocaine after not reporting use (discordant reporting). Of the 328 who provided a sample, cocaine and ketamine were the most frequently detected drugs (55.2% [n = 181] and 37.2% [n = 122], respectively), but these were also the two most underreported drugs, with 37.1% (n = 65) and 26.4% (n = 65), respectively, testing positive after not reporting use. Between 2019 and 2022, positivity decreased for cocaine, ketamine, 3,4-methylenedioxy-metamfetamine, and amfetamine, and underreported exposure to cocaine and ketamine also decreased (P Underreporting of drug use was common, suggesting the need for researchers to better deduce intentional underreporting versus unknown drug exposure via adulterants. Researchers should consider both self-report and toxicology results from biological samples when examining trends in use.