Assessing self-reported use of new psychoactive substances: The impact of gate questions

Background: New psychoactive substances (NPS) continue to emerge; however, few surveys of substance use ask about NPS use. Research is needed to determine how to most effectively query use of NPS and other uncommon drugs.Objective: To determine whether prevalence of self-reported lifetime and past-year use differs depending on whether or not queries about NPS use are preceded by gate questions. Gate questions utilize skip-logic, such that only a yes response to the use of specific drug class is followed by more extensive queries of drug use in that drug class.Methods: We surveyed 1,048 nightclub and dance festival attendees (42.6% female) entering randomly selected venues in New York City in 2016. Participants were randomized to gate vs. no gate question before each drug category. Analyses focus on eight categories classifying 145 compounds: NBOMe, 2C, DOx, bath salts (synthetic cathinones), other stimulants, tryptamines, dissociatives, and non-phenethylamine psychedelics. Participants, however, were asked about specific bath salts regardless of their response to the gate question to test reliability. We examined whether prevalence of use of each category differed by gate condition and whether gate effects were moderated by participant demographics.Results: Prevalence of use of DOx, other stimulants, and non-phenethylamine psychedelics was higher without a gate question. Gate effects for other stimulants and non-phenethylamine psychedelics were larger among white participants and those attending parties less frequently. Almost one in ten (9.3%) participants reporting no bath salt use via the gate question later reported use of a bath salt such as mephedrone, methedrone, or methylone.Conclusion: Omitting gate questions may improve accuracy of data collected via self-report.