Polydrug Use Typologies of Regular Ecstasy Users Visiting Electronic Dance Music Events: A Latent Class Analysis.

Introduction: Polydrug use patterns among young adults using ecstasy vary, as well as their willingness to change them. Polydrug use patterns are likely associated with different adverse health outcomes. It is unknown whether polydrug use patterns of young adults who use ecstasy are similar in different countries.

Impulse control disorders associated with dopaminergic drugs: A disproportionality analysis using vigibase.

Background: Dopamine receptor agonist drugs, which are used, for example, to treat Parkinson's disease (PD), increase the risk for impulse control disorders (ICDs), potentially resulting in devastating psychosocial consequences. It is unknown whether other drugs with dopaminergic properties also increase the risk for ICDs. This study assesses the disproportionality of reporting ICDs between drugs with dopaminergic properties and selected non-dopaminergic drugs.

Drug Use Changes at the Individual Level: Results from a Longitudinal, Multisite Survey in Young Europeans Frequenting the Nightlife Scene.

Background: Monitoring emerging trends in the increasingly dynamic European drug market is vital; however, information on change at the individual level is scarce. In the current study, we investigated changes in drug use over 12 months in European nightlife attendees.

Method: In this longitudinal online survey, changes in substances used, use frequency in continued users, and relative initiation of use at follow-up were assessed for 20 different substances.

"How do online and offline sampling compare in a multinational study of drug use and nightlife behaviour?".

Background: Online sampling is widely used to recruit hard to reach samples such as drug users at nightlife events. We conducted the first study comparing differences in demographics, drug use and nightlife behaviour between an online sample of young adults engaging with the European nightlife scene, and an offline sample recruited at nightclubs and festivals in Europe.

Methods: Online participants who attended at least six nightlife events in the past 12 months were recruited using social media advertising (May-November 2017).

Changes in cannabis potency and first-time admissions to drug treatment: a 16-year study in the Netherlands.

Background: The number of people entering specialist drug treatment for cannabis problems has increased considerably in recent years. The reasons for this are unclear, but rising cannabis potency could be a contributing factor.

Methods: Cannabis potency data were obtained from an ongoing monitoring programme in the Netherlands.

Purity, adulteration and price of drugs bought on-line versus off-line in the Netherlands.

Background And Aims: On-line drug markets flourish and consumers have high expectations of on-line quality and drug value. The aim of this study was to (i) describe on-line drug purchases and (ii) compare on-line with off-line purchased drugs regarding purity, adulteration and price.

Design: Comparison of laboratory analyses of 32 663 drug consumer samples (stimulants and hallucinogens) purchased between January 2013 and January 2016, 928 of which were bought on-line.

Limitations to the Dutch cannabis toleration policy: Assumptions underlying the reclassification of cannabis above 15% THC.

The Netherlands has seen an increase in Δ9-tetrahydrocannabinol (THC) concentrations from approximately 8% in the 1990s up to 20% in 2004. Increased cannabis potency may lead to higher THC-exposure and cannabis related harm. The Dutch government officially condones the sale of cannabis from so called 'coffee shops', and the Opium Act distinguishes cannabis as a Schedule II drug with 'acceptable risk' from other drugs with 'unacceptable risk' (Schedule I).

Validity of sidestream endtidal carbon dioxide measurement in critically ill, mechanically ventilated children.

Introduction: Capnography is used to monitor the endtidal carbon dioxide tension (EtCO2) in exhaled gas. Sidestream capnography has great potential to monitor mechanically ventilated pediatric patients, given the continuous sampling from the endotracheal tube into a gas sensor. However, hemodynamic and respiratory impairments may reduce reliability and validity of sidestream capnography to monitor arterial carbon dioxide tension (PaCO2) in critically ill, mechanically ventilated children.

Three-Year Course of Cannabis Dependence and Prediction of Persistence.

Aims: To examine the course and the predictors of the persistence of cannabis dependence.

Methods: Through cannabis outlets and chain referral, a prospective enriched community cohort of 207 young adults (aged 18-30) with DSM-IV cannabis dependence at baseline (T0) was formed and followed-up after 1.5 (T1) and 3 (T2) years.

The Missing=Smoking Assumption: A Fallacy in Internet-Based Smoking Cessation Trials?

Introduction: In this study, penalized imputation (PI), a common approach to handle missing smoking status data and sometimes referred to as "missing=smoking," is compared with other missing data approaches using data from internet-based smoking cessation trials. Two hypotheses were tested: (1) PI leads to more conservative effect estimates than complete observations analysis; and (2) PI and multiple imputation (MI) lead to similar effect estimates under balanced (equal missingness proportions among the trial arms) and unbalanced missingness.

Methods: First, the outcomes of 22 trials included in a recent Cochrane review on internet-based smoking cessation interventions were reanalyzed using only the complete observations, and after applying PI.

Reliability and validity of the Marijuana Motives Measure among young adult frequent cannabis users and associations with cannabis dependence.

The Marijuana Motives Measure (MMM) has so far been examined mainly in student populations, often with relatively limited involvement in cannabis use. This study evaluated the factor structure of the MMM in a demographically mixed sample of 600 young adult (18-30 years) frequent (≥ 3 days per week) cannabis users in the Netherlands. Analysis confirmed a five-factor solution, denoting coping, enhancement, social, conformity and expansion motives.

The role of leisure and delinquency in frequent cannabis use and dependence trajectories among young adults.

Background: The link between leisure and cannabis use has been widely studied, but less so for young adults, and rarely with a focus on frequent cannabis use. Also, little is known about how changes in leisure develop over time and how they are related to transitions in cannabis use and dependence.

Method: As part of a 3-year longitudinal project, in a qualitative study 47 frequent male and female young adult cannabis users with (n=23) and without (n=24) dependence at baseline were interviewed in-depth after 1.

Cross-sectional and prospective relation of cannabis potency, dosing and smoking behaviour with cannabis dependence: an ecological study.

Background And Aims: Increased delta-9-tetrahydrocannabinol (THC) concentrations in cannabis may lead to higher THC exposure, cannabis dependence and treatment need, but users may also adapt the actual intake of THC through reduced inhalation of THC containing smoke (titration). We investigated whether consumers of stronger cannabis use less cannabis per joint or inhale less smoke than those using less potent cannabis and whether these factors predict cannabis dependence severity.

Methods: Heavy cannabis users (n = 98) brought their own cannabis, rolled a joint and smoked it ad libitum in a naturalistic setting.

Facilitators and barriers in treatment seeking for cannabis dependence.

Background: Relatively few cannabis dependent people seek treatment and little is known about determinants of treatment seeking.

Methods: Treatment determinants were compared among 70 DSM-IV cannabis dependent patients and 241 non-treatment seeking DSM-IV cannabis dependent community subjects. In addition, perceived facilitators for treatment seeking were assessed in patients, whereas perceived barriers were assessed in 160/241 cannabis dependent community subjects not prepared to seek treatment (precluders), of whom 63/160 showed an objective treatment need, and 30/241 showed a subjective treatment need.

The Role of Study and Work in Cannabis Use and Dependence Trajectories among Young Adult Frequent Cannabis Users.

Life course theory considers events in study and work as potential turning points in deviance, including illicit drug use. This qualitative study explores the role of occupational life in cannabis use and dependence in young adults. Two and three years after the initial structured interview, 47 at baseline frequent cannabis users were interviewed in-depth about the dynamics underlying changes in their cannabis use and dependence.

Predicting the transition from frequent cannabis use to cannabis dependence: a three-year prospective study.

Background: Frequent cannabis users are at high risk of dependence, still most (near) daily users are not dependent. It is unknown why some frequent users develop dependence, whereas others do not. This study aims to identify predictors of first-incidence DSM-IV cannabis dependence in frequent cannabis users.

Reliability and validity of the Severity of Dependence Scale for detecting cannabis dependence in frequent cannabis users.

The Severity of Dependence Scale (SDS) measures with five items the degree of psychological dependence on several illicit drugs, including cannabis. Its psychometric properties have not yet been examined in young adult frequent cannabis users, an eminently high-risk group for cannabis dependence. Internal consistency and criterion validity of the SDS were investigated within an enriched community based sample of 577 Dutch frequent (≥ three days per week in the past 12 months) cannabis users between 18-30 years.

Validation of self-reported cannabis dose and potency: an ecological study.

Aims: To assess the reliability and validity of self-reported cannabis dose and potency measures.

Design: Cross-sectional study comparing self-reports with objective measures of amount of cannabis and delta-9-tetrahydrocannabinol (THC) concentration.

Setting: Ecological study with assessments at participants' homes or in a coffee shop.

Reference values of exhaled nitric oxide in healthy children 1-5 years using off-line tidal breathing.

Measurement of the fraction of exhaled nitric oxide (FeNO) is a useful test to diagnose and/or monitor eosinophilic airway inflammation. The off-line tidal breathing method is used for measurements in young children, but reference values for preschool children are scarce. The objective of this study was to establish reference values for FeNO in healthy children 1-5 years old.

Mental health differences between frequent cannabis users with and without dependence and the general population.

Aims: To compare the prevalence of mental disorders between frequent cannabis users with and without dependence and the general population.

Design: Cross-sectional comparison of interview data.

Setting: Enriched community sample of frequent cannabis users and a representative sample of non-users and non-frequent users from the general population.

The Dutch Cannabis Dependence (CanDep) study on the course of frequent cannabis use and dependence: objectives, methods and sample characteristics.

This paper presents an overview of the prospective cohort design of the Dutch Cannabis Dependence (CanDep) study, which investigates (i) the three-year natural course of frequent cannabis use (≥ three days per week in the past 12 months) and cannabis dependence; and (ii) the factors involved in the transition from frequent non-dependent cannabis use to cannabis dependence, and remission from dependence. Besides its scientific relevance, this knowledge may contribute to improve selective and indicated prevention, early detection, treatment and cannabis policies. The secondary objectives are the identification of factors related to treatment seeking and the validation of self report measures of cannabis use.