Visitors of the Dutch drug checking services: Profile and drug use experience

Illegal drug production and large seizures of substances such as amphetamines and cocaine mean that people who use drugs (PWUD) often do not know the dose, purity or contaminants of what they have purchased, increasing the risk of harm. Drug checking services (DCS) have been established in several countries since the early 1990s to provide information about sample composition and to offer personalised feedback as a harm reduction and monitoring tool. The Dutch Drugs Information and Monitoring System (DIMS) operates a coordinating office and 31 fixed-site DCS where anonymous, voluntary sample submission is paired with a private consultation focused on reducing health risks. This study sets out to describe the demographic and drug use characteristics of visitors to eight participating DIMS facilities during 2018 and to examine their prior drug experience. The investigators aim to provide insight into who uses Dutch DCS, whether visitors are already experienced drug users, and whether DCS might plausibly encourage initiation of drug use. The report addresses a gap in recent descriptive data on the DIMS client population, as the most recent comprehensive description was nearly twenty years old.

Between March and December 2018, visitors to eight DIMS sites in medium-sized to large Dutch cities were invited, via waiting-room posters and staff invitations, to complete a pen-and-paper questionnaire while awaiting their consultation. Participation was voluntary, anonymous and one-off; questionnaires were dropped into a closed box and responses were not discussed during the private consultation. An initial 1,774 questionnaires were collected; 244 were identified as repeat participations and excluded, leaving a final dataset of 1,530 unique participants who together submitted 1,899 drug samples for testing. The eight sites together accounted for approximately 63% of nationally submitted samples in 2018. Data collection was performed as part of routine service provision and was exempt from specific ethical approval under Dutch law. The questionnaire recorded demographics (gender, age, migration background, highest level of education), nightlife behaviour (frequency of visiting bars, clubs, festivals; alcohol and tobacco use on a night out and on a normal day), and drug use. Drug measures included lifetime and last-year prevalence and time since first use for MDMA, amphetamine, cocaine, 4-FA, 2C-B, LSD, cannabis, nitrous oxide and twelve other listed drugs; respondents also reported the drug sample they submitted for analysis. Analyses were descriptive. The researchers calculated percentages, means and standard deviations using IBM SPSS Statistics Version 25. No inferential or multivariable analyses are reported in the extracted text.

The final sample comprised 1,530 participants (submitting 1,899 samples). Participants were predominantly male (63.2%) and concentrated in their twenties (59.1%), with an age range from 16 to 74 years (mean 28.5, SD 9.4). Most did not have a migration background (83.8%) and a large majority were enrolled in or had completed university education (76.1%). The participating sites together represented about 15% of the 12,634 drug samples submitted nationwide in 2018. Visitors reported high levels of nightlife attendance and substance use associated with nights out. Monthly attendance was common: 73.2% visited bars, 52.0% clubs and 25.6% music festivals at least once a month. On a day out, 88.6% reported drinking alcohol (mean 8.6 glasses, SD 4.9) and 58.7% smoked (mean 9.9 cigarettes, SD 8.8). On a 'normal' day, 69.4% drank alcohol (mean 3.0 glasses, SD 2.5) and 35.0% smoked (mean 7.2 cigarettes, SD 6.6). Experience with drugs was widespread. Lifetime prevalence was 86.2% for cannabis and 93.0% for MDMA among participants, and fewer than 0.7% reported never having used any of the twenty drugs listed in the questionnaire. Most participants had begun using drugs at least three years previously and 96.8% reported drug use in the previous year. Analyses by subsample (based on the drug submitted at the visit) showed that a majority submitted MDMA samples (1,013 participants). Smaller subsamples submitted amphetamine (53), cocaine (42), 4-FA (50), 2C‑B (52) or LSD (36); the remaining 284 submitted other, multiple, unknown or unrecorded drugs. Although more than half the full sample had never used amphetamine, cocaine, 4-FA, 2C‑B or LSD, those who submitted these specific drugs tended to have prior experience with them. For example, amphetamine had a lifetime prevalence of 44.5% in the total sample, but 90.4% within the subsample who submitted amphetamine; the average time since first amphetamine use in that subsample exceeded eight years. A large majority of those submitting MDMA, amphetamine, cocaine or 4‑FA had used the submitted drug previously, whereas roughly half of those submitting 2C‑B or LSD had prior use of that specific drug but generally had experience with other drugs.

Pieter and colleagues interpret the findings as indicating that typical visitors to the DIMS DCS are young, male, highly educated nightlife attendees without a migration background, and that this profile is similar to what other studies have reported. The investigators highlight that this group is likely to be 'hidden' from traditional addiction services: earlier research suggests many DCS visitors have not previously accessed drug or alcohol services, which supports the view that DCS can engage populations that are harder to reach through conventional public health channels. At the same time, the study team emphasises a selective reach. Participants with lower educational attainment and those with a migration background were underrepresented relative to national population figures (the authors note that about 30% of the general population are classified as higher educated and 23% have a migration background). Although national MDMA prevalence is lower among people with lower education, similar prevalence across migration status suggests DCS outreach could be broadened to better include underrepresented groups. The authors consider lower study participation among these groups as one possible cause of underrepresentation but report no evidence from their data to substantiate that explanation. With respect to whether DCS encourage initiation of drug use, the investigators argue it is unlikely: almost all visitors already had prior drug experience, and those who submitted a drug they had not personally used were typically experienced with other drugs. The authors suggest that if people choose to use a substance, doing so after testing and after receiving harm reduction advice is preferable to using an untested product of unknown content. The researchers acknowledge several limitations that constrain generalisability. The respondents' 1,899 samples represent roughly 15% of all samples submitted nationally in 2018, but unique visitor figures and non-response information are lacking, so the proportion and selectivity of non-participation is unknown. Consequently, results cannot be assumed to represent all DIMS visitors or PWUD in general. Finally, the authors note that DCS visitors may be more inclined toward health-promoting behaviours than the broader population of people who use drugs.

The authors conclude that drug checking can be a valuable tool for addiction care and public health services in reaching more difficult-to-reach PWUD, particularly young nightlife-attending people who can benefit from harm reduction strategies. They caution that DCS may not be easily accessible to all demographic groups and state it is unlikely that DCS encourage first-time drug use, since most visitors already have drug experience.