How to ask about the use of new psychoactive substances to increase the validity of results in self-report prevalence surveys.

INTRODUCTION AND AIMS: New psychoactive substances (NPS) represent hundreds of novel compounds. However, the general public might not be familiar with the overarching term NPS. This can result in both under- and over-reporting of NPS use. DESIGN AND METHODS: The study analysed the last-year prevalence of NPS use in an online survey conducted across I-TREND project countries (the Czech Republic, the Netherlands and Poland). Self-reported NPS use was assessed within two types of questions-a generic and a checklist question. We analysed prevalence for each question separately, incorporated the free-text probe 'other' that followed them, and combined the two questions into a conservative and an inclusive estimate. RESULTS: Including free-text responses to the 'other' categories increased prevalence of NPS use (from 51% to 56% for the checklist question and 25% to 32% for the generic question). Taking an inclusive approach to estimating prevalence (i.e. indicating NPS use in either a generic list or from the checklist) yielded a higher prevalence estimate (60%, 95% confidence interval 58-62%), compared to a more conservative approach in which NPS use had to be affirmed by both questions (27%, 95% confidence interval 26-29%). DISCUSSION AND CONCLUSIONS: Generic questions might lead to notably lower estimates of self-reported NPS use in comparison to checklists. However, creating relevant checklists is challenging and lengthy survey instruments have limitations. Further surveys might benefit from featuring a combination of the strategies used in this study-a single (generic) question involving a number of locally specific NPSs and a free-text 'other' probe.

Estimating the size of crack cocaine users in France: Methods for an elusive population with high heterogeneity.

BACKGROUND: Despite several sources corroborating an expanding market and increased visibility and greater diversity in users' profiles, very little is known about the number of crack cocaine users in France. METHOD: The estimates rely on a single data source capture-recapture method. Annual data are extracted from treatment centres nationwide. To account for heterogeneity, we use an innovative zero-truncated geometric, regression-based estimator controlling for individual and centre characteristics. We use the well-known Zelterman estimator as a benchmark. RESULTS: The number of crack cocaine users received in treatment centres increased dramatically, from 3388 in 2010 to 5143 in 2017 (+52%). The estimated number of crack cocaine users is believed to have tripled over the course of the same period (from 9775, 95% CI [8288-11530] to 28983 [24876-33766], respectively), with prevalences below 1‰, similar to other European countries. The coverage rate (observed number/estimated number of users) decreased in a similar fashion, indicating lower utilization. In particular, females and younger users are underestimated by data from treatment centres. CONCLUSION: The prevalence of crack cocaine use is fairly low but steadily increasing. The diversity in users' profiles is a challenge to prevention and public health policies that should expand their scope to a more inclusive perspective of what defines crack cocaine users. Our method overcomes several methodological issues (data sources, data linkage, heterogeneity) and can be easily applied to a wide range of settings.

Age of Initiation and Patterns of Use among People Who Inject Drugs Welcomed in Harm Reduction Facilities in France from 2006 to 2015.

This exploratory analysis of time-series cross-sectional data provides insights on trends in age at first injection among people who inject drugs in France, and on associations with recent risky injecting behaviors. Data were collected from a national survey conducted in harm reduction facilities in five phases between 2006 and 2015. Standardized questionnaires collected information on demographics, substance use, and route of administration, as well as lifetime and past-month injection. Descriptive and multilevel models were applied to account for the hierarchical structure of the data. Prevalence of lifetime and past-month injection remained stable over time, while the prevalence of daily injection increased significantly. Mean age at first injection only appeared to increase for data collected after 2010. Gender differences in mean age at first injection decreased over time, suggesting the development of converging patterns of initiation independent of sex. After controlling for covariates, early initiation of injection was unrelated to daily injection or material sharing, and associated with the number of recently injected substances. Early initiation is likely a predictor of injected polysubstance use. Findings are relevant to the planning, implementation, and evaluation of prevention programs.

Determinants of heroin retail prices in metropolitan France: Discounts, purity and local markets.

INTRODUCTION AND AIMS: Field studies have indicated a recent increase in heroin availability and use in France, and yet very little is known about the mechanisms underlying heroin retail prices. This paper offers a first attempt at identifying the determinants of heroin pricing, to measure quantity discounts and assess the influence of purity on street prices, while controlling for a geographical effect. DESIGN AND METHODS: Data on heroin samples were collected during 2011 in seven urban areas of metropolitan France. Ordinary least squares regression was used to model the associations between price, quantity, purity and other independent variables. RESULTS: Quantity remains the most influential variable on heroin pricing. We estimate that a 10% increase in the size of a transaction leads to a 2.3% decrease in the unit price. Assessed purity proved to be significant, although in modest proportion. Sociodemographic characteristics, such as gender, users' experience and relationships with dealers, proved to be insignificant. Heroin retail prices vary according to a geographical gradient related to the routes of entry and distribution. DISCUSSION AND CONCLUSIONS: As a credence good, heroin retail prices in France are affected by more than simply the traditional supply and demand relationship. The results of this study also underline the limitations of a quantitative framework and should be complemented by further ethnographic research to obtain an in-depth understanding of local markets. Policies should be designed to better take local disparities into account.[Lahaie E, Janssen E, Cadet-Taïrou A. Determinants of heroin retail prices in metropolitan France:Discounts, purity and local markets. Drug Alcohol Rev 2016;35:597-604].

Composition, purity and perceived quality of street cocaine in France.

BACKGROUND: There is little knowledge about the composition and cocaine content of street cocaine, nor about what users know about it. METHOD: 373 cocaine users were face to face interviewed between May and December 2006 about the last sample of cocaine they had consumed and residual amounts of the substances actually used were analysed using gas phase chromatography coupled to mass spectrometry (GC-MS). Users rated the perceived quality of their product ("good", "average", "poor"), its "estimated percentage of cocaine" and any cutting agents it contained. Price, quantity, place of purchase (street, dealer's premise, appointment), mode of administration (sniffing, injection, smoking) and the supposed nature of the sample (natural, synthetic, no distinction ever made) were also reported. Perceived quality was modelled using multivariate multinomial regression. RESULTS: The median cocaine content was 22%. Altogether, 343 samples contained cocaine, among which 75% contained at least one adulterant. The most frequently occurring were phenacetin (54% of the samples), caffeine (17%), paracetamol (14%), diltiazem and lidocaïne (11%). Users showed relatively poor discrimination concerning cocaine purity, and only 12% reported at least one of the detected adulterants. The major determinants of their perception of cocaine quality were: place of purchase, natural origin, price per gram, actual cocaine content and mode of administration. CONCLUSION: The composition of street cocaine is largely unknown to users. Users' perceptions of cocaine quality are based partly on false beliefs and certain administration modes. This may contribute to favouring very risky practices. The effects of adulterants on users' health should be investigated.

The contemporary uses of hallucinogenic plants and mushrooms: a qualitative exploratory study carried out in France.

This qualitative research implemented in France between 2004 and 2007 is based on 30 in-depth interviews carried out with individuals who consumed hallucinogenic plants or mushrooms at least six times during the year preceding the interview. The interviews were recorded, retranscribed, and an analysis of their content applied for the textual data. The study focuses on drug users and the meanings they attach to their drug use. These meanings involve three different representations of the drugs: "enchanting plants," "disorientation plants," and "visionary plants."