How Cannabis Users Obtain and Purchase Cannabis: A Comparison of Cannabis Users from European Countries with Different Cannabis Policies

Objective: This study examines the role of cannabis policy in how cannabis users obtain and purchase cannabis. Methods: A survey was conducted in the Dutch coffeeshops among current cannabis users (n = 1255) aged 18-40 from seven European countries with different cannabis policies. This study investigated whether acquisition methods and supply sources were associated with national cannabis policy, controlling for gender, age, and frequency of use. Results: Cross-national differences notwithstanding, cannabis was easily available to current cannabis users in Europe. Within and across countries, users acquired cannabis in various ways and buyers purchased it from various sources, representing a mixture of open, closed, and semi-open retail markets. Buying cannabis was the most common method of acquisition. Among participants who reported buying their cannabis (n = 929), buying from friends was the most common source of supply, followed by street dealers, home dealers, and delivery services. The vast majority of Dutch participants reported buying cannabis from coffeeshops. Contrariwise, French buyers were more likely to buy cannabis from street dealers and delivery services, and Greek buyers to buy it from home dealers and friends. Overall, the Internet played a marginal role in purchasing cannabis. Conclusion: Our findings confirm the significant role of social supply across Europe. Although cross-national differences were rather common in cannabis acquisition and supply, yet they were not unidirectionally linked with the punitiveness of national cannabis policy. Findings suggest a differentiated normalization of the cannabis retail market, with users often preferring to buy cannabis in a regulated or legal market.

An Exploratory Study of Cannabis Festivals and Their Attendees in Two European Cities: Amsterdam and Berlin

This study was designed to explore the nature and features of cannabis festivals, characteristics of festival participants, and reasons for attendance. A field study in two European cities (Amsterdam and Berlin) included participant observation at the festivals, interviews with local organizers, and a survey among festival attendees (n = 728). Both festivals had common features, but also showed distinct differences. At both festivals, nine out of 10 participants were current, often daily cannabis users. Participants were mainly young adults (mean = 26.2 years), but younger in Berlin than in Amsterdam. Common reasons for festival attendance were "protest/activism" and "entertainment." Protest/activism was more likely in Berlin, among daily cannabis users, and participants aged 25+ years. Entertainment was more likely in Amsterdam, among non-daily cannabis users, and participants younger than 25 years. Although similar in political aim, cannabis festivals are characterized by distinctive local features, as well as differences in attendee profile and reasons for festival participation. Findings suggest that the latter differences are driven by differences in cannabis policy, with a stronger tendency towards protest/activism in countries with a less liberal, or more restrictive, cannabis policy. Future research should include more countries, representing a wider variation in cannabis policies.

Cross-National Differences in Drugs and Violence among Adolescents: Preliminary Findings of the DAVI Study

The purpose of this paper is to describe cross-national differences in drug use and violence among three sites that vary in social and political culture and drug use policies—Philadelphia, Toronto, and Amsterdam. The DAVI (Drugs, Alcohol and Violence International) study is based on personal interviews with 1,120 adolescents aged 14 to 17 years from three sites and two samples (550 detainees and 570 dropouts). Seven drug use outcomes and three violence outcomes were compared across sites. We found that site differences were dominant. Only two of 10 outcomes (cannabis onset and relative drug-related violence) were not significantly related to site as a main effect or through an interaction. The most common site differences showed that the Toronto samples reported higher rates of drug use than Philadelphia and Amsterdam. Our findings indicate that drug taking behavior transcends geopolitical boundaries and that there is no clear evidence that rates of drug use are related to policy climate.

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. Additionally, the original MMM was extended with two items (boredom and habit), which formed a distinct, internally consistent sixth factor labelled routine motives. In a multivariable logistic regression analysis, coping and routine motives showed significant associations with 12-month DSM-IV cannabis dependence. The results suggest general reliability and validity of the MMM in a heterogeneous population of experienced cannabis users.

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 presence of cannabis dependence, cannabis-related problems, functional impairment and treatment was assessed using the Composite International Diagnostic Interview (CIDI 3.0) and the Sheehan Disability Scale (SDS). Predictors of persistence were lifetime cannabis abuse and dependence symptoms, cannabis use characteristics, distant vulnerability factors (e.g. childhood adversity, family history of psychological/substance use problems, impulsivity, mental disorders), and proximal stress factors (recent life events, social support).

RESULTS

Four groups were distinguished: persistent dependent (DDD: 28.0%), stable non-persistent (DNN: 40.6%), late non-persistent (DDN: 17.9%) and recurrent dependent (DND: 13.5%). At T2, persisters (DDD) reported significantly more (heavy) cannabis use and cannabis problems than non-persisters (DNN/DDN/DND). Treatment seeking for cannabis-related problems was rare, even among persisters (15.5%). The number (OR = 1.23 (1.03-1.48)) and type ('role impairment' OR = 2.85 (1.11-7.31), 'use despite problems' OR = 2.34 (1.15-4.76)) of lifetime cannabis abuse/dependence symptoms were the only independent predictors of persistence with a total explained variance of 8.8%.

CONCLUSIONS

Persistence of cannabis dependence in the community is low, difficult to predict, and associated with a negative outcome. The substantial proportion of stable non-persisters suggests that screening and monitoring or low-threshold brief interventions may suffice for many non-treatment-seeking cannabis-dependent people. However, those with many lifetime abuse/dependence symptoms may benefit from more intensive interventions.

Criminal involvement and crime specialization among crack users in the Netherlands

BACKGROUND/AIMS

Crack users in the Netherlands are an ageing and diverse population with longstanding criminal careers. Our aim was to assess factors associated with current criminal involvement and specialization in selling drugs, property crime and violence.

METHOD

A sample of 1,039 frequent crack users was recruited in three major Dutch cities, combining respondent-driven sampling with random institutional sampling. Bivariate and logistic regression analyses were performed to find factors associated with current criminality.

RESULTS

A total of 431 participants (41.5%) had engaged in crime in the past 30 days, mostly selling drugs (68.9%), followed by property crimes (34.4%) and a few cases of violent crime (9.7%). Younger age, homelessness, heavier patterns of use and a more prolific criminal justice history were associated with current criminality. Those receiving welfare benefits tended to be more likely to specialize only in selling drugs as opposed to (also) property crimes.

CONCLUSION

Reducing drug use among criminally involved crack users and addressing their housing conditions could have a significant impact on reducing drug-related crime. Welfare benefits might act as protective factor against committing property crimes but not against the selling of drugs.

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 1.5 and 3 years.

RESULTS

Frequent cannabis users (at baseline ≥3 days per week in the past 12 months) are involved in similar leisure activities as the general young adult population and live rather conventional lives, generally away from a delinquent subculture. They mostly regulate their cannabis use to leisure time, to enhance other leisure activities, including socialising and video gaming. While they often give precedence to responsibilities (e.g. work and study), dependent and non-dependent users differed in whether they actively adapted their leisure activities to their cannabis use, or their cannabis use to their leisure time. Both types of and time spent on leisure activities were associated with transitions in use and dependence.

CONCLUSIONS

While our findings generally support the normalisation thesis, it is questionable whether frequent but non-problematic cannabis use is socially accepted in wider society. This study also questions the diagnostic dependence vs. non-dependence dichotomy, and adds finer distinctions to the concept of cannabis dependence. Implications for prevention and treatment include facilitating structured spending of leisure time (e.g. sports), and targeting frequent users who spent much leisure time video gaming at home.

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. We analysed the content of the joint, its association with smoking behaviour and the cross-sectional and prospective (1.5-year follow-up) relations between smoking behaviour and cannabis dependence severity (total number of DSM-IV dependence symptoms).

RESULTS

THC concentration in cannabis (range 1.10-24.70%) was correlated positively with cannabis dose per joint (b = 0.008, P = 0.01), but the resulting THC concentration per joint (range 0.24-15.72%) was associated negatively with inhalation volume (b = -0.05, P = 0.03). Smoking behaviour measures (number of puffs, inhaled volume, reduction of puff volume and puff duration while smoking) predicted follow-up dependence severity, independently of baseline dependence severity and monthly THC dose (number of joints × cannabis dose × cannabis THC concentration). Monthly THC dose only predicted follow-up dependence severity when unadjusted for baseline severity.

CONCLUSIONS

Cannabis users titrate their delta-9-tetrahydrocannabinol intake by inhaling lower volumes of smoke when smoking strong joints, but this does not fully compensate for the higher cannabis doses per joint when using strong cannabis. Thus, users of more potent cannabis are generally exposed to more delta-9-tetrahydrocannabinol. Smoking behaviour appears to be a stronger predictor for cannabis dependence severity than monthly delta-9-tetrahydrocannabinol dose.

Risk factors of γ-hydroxybutyrate overdosing

The aim of this study was to identify in recreational drug users the factors which increase the risk of overdosing (OD) with γ-hydroxybutyrate (GHB). A purposive sample of 45 experienced GHB users was interviewed, equally divided into three groups (never OD, occasional OD, and repeat OD). The repeat OD group scored highest on many risk factors regarding GHB use, the occasional OD group scored intermediate, and the never OD group scored lowest. Participants, whether or not they had overdosed on GHB, most often perceived GHB use (e.g. using more GHB than usual, using GHB doses too closely together) as the main reason for GHB OD, and many participants who had overdosed on GHB reported that they had taken more GHB than usual at their most recent occasion of GHB OD. No significant differences in co-use of GHB with other substances were found between the three groups. Our findings indicate that using GHB in the company of groups of friends probably reduces, but does not eliminate, the risk of OD.

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.

METHODS

A prospective cohort of frequent cannabis users (aged 18-30, n=600) with baseline and two follow-up assessments (18 and 36 months) was used. Only participants without lifetime diagnosis of DSM-IV cannabis dependence at baseline (n=269) were selected. Incidence of DSM-IV cannabis dependence was established using the Composite International Diagnostic Interview version 3.0. Variables assessed as potential predictors of the development of cannabis dependence included sociodemographic factors, cannabis use variables (e.g., motives, consumption habits, cannabis exposure), vulnerability factors (e.g., childhood adversity, family history of mental disorders or substance use problems, personality, mental disorders), and stress factors (e.g., life events, social support).

RESULTS

Three-year cumulative incidence of cannabis dependence was 37.2% (95% CI=30.7-43.8%). Independent predictors of the first incidence of cannabis dependence included: living alone, coping motives for cannabis use, number and type of recent negative life events (major financial problems), and number and type of cannabis use disorder symptoms (impaired control over use). Cannabis exposure variables and stable vulnerability factors did not independently predict first incidence of cannabis dependence.

CONCLUSIONS

In a high risk population of young adult frequent cannabis users, current problems are more important predictors of first incidence cannabis dependence than the level and type of cannabis exposure and stable vulnerability factors.

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.

RESULTS

Compared to non-treatment seekers, patients reported more cannabis use (176.9 versus 82.8 joints monthly), more symptoms of dependence (5.6 versus 4.5), higher perceived lack of social support (70.0% versus 41.1%), more pressure to seek treatment (58.6% versus 21.6%), a more positive attitude to treatment, and more previous treatments. In addition, patients reported more mental health problems (internalising disorders 57.1% versus 24.5%; externalising disorders 52.9% versus 35.3%) and more functional impairments (8.4 versus 4.8 monthly days out of role). Cannabis dependent 'precluders' reported desire for self-reliance (50.0%), preference for informal help (22.5%), and absent treatment need (16.9%) as their main reasons not to seek treatment, whereas cannabis dependent community subjects with a subjective treatment need mainly expressed desire for self-reliance (36.7%), treatment ineffectiveness (16.7%), and avoiding stigma (13.3%).

CONCLUSIONS

Functional impairment, mental health problems and social pressure are important reasons to seek treatment in people with cannabis dependence. Treatment participation might improve if desire for self-reliance and the preference for informal help are considered, and perceived ineffectiveness of treatment and stigmatisation are publicly addressed.

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.

PARTICIPANTS

Young adult frequent cannabis users (n = 106) from the Dutch Cannabis Dependence (CanDep) study.

MEASUREMENTS

The objectively measured amount of cannabis per joint (dose in grams) was compared with self-reported estimates using a prompt card and average number of joints made from 1 g of cannabis. In addition, objectively assessed THC concentration in the participant's cannabis was compared with self-reported level of intoxication, subjective estimate of cannabis potency and price per gram of cannabis.

FINDINGS

Objective estimates of doses per joint (0.07-0.88 g/joint) and cannabis potency (1.1-24.7%) varied widely. Self-reported measures of dose were imprecise, but at group level, average dose per joint was estimated accurately with the number of joints made from 1 g [limit of agreement (LOA) = -0.02 g, 95% confidence interval (CI) = -0.29; 0.26], whereas the prompt card resulted in serious underestimation (LOA = 0.14 g, 95% CI = -0.10; 0.37). THC concentration in cannabis was associated with subjective potency ['average' 3.77% (P = 0.002) and '(very) strong' 5.13% more THC (P < 0.001) than '(very) mild' cannabis] and with cannabis price (about 1% increase in THC concentration per euro spent on 1 g of cannabis, P < 0.001), but not with level of intoxication.

CONCLUSIONS

Self-report measures relating to cannabis use appear at best to be associated weakly with objective measures. Of the self-report measures, number of joints per gram, cannabis price and subjective potency have at least some validity.

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.

PARTICIPANTS

A total of 521 young adult (aged 18-30 years) frequent cannabis users, 252 of whom were with DSM-IV cannabis dependence (D+) and 269 without DSM-IV cannabis dependence (D-), and 1072 young adults from the general population.

MEASUREMENTS

Multinomial logistic regression was used to compare groups regarding the presence of DSM-IV mental disorders. Detailed measures of cannabis use, childhood adversity and other substance use were considered confounders.

FINDINGS

Compared with the general population, externalizing disorders were more prevalent in D- [odds ratio (OR) = 8.91, P < 0.001] and most prevalent in D+ (OR = 17.75, P < 0.001), but internalizing disorders were associated only with D+ (mood OR = 4.15, P < 0.001; anxiety OR = 2.20, P = 0.002). Associations were attenuated (and often became non-significant) after correction for childhood adversity and substance use other than cannabis. However, the prevalence of mental disorders remained higher in D+ compared with D- (OR = 2.40, P < 0.001), although cannabis use patterns were remarkably similar.

CONCLUSIONS

Cannabis use patterns, childhood adversity and the use of other substances are similar in dependent and non-dependent frequent cannabis users. With the exception of more externalizing disorders, the mental health condition of non-dependent frequent cannabis users is similar to that of the general population, whereas it is worse in dependent frequent cannabis users.

Buying and Selling Crack

To assess key characteristics of the retail crack market and the role of users as buyers and sellers, data from a survey inside and outside institutional setting among 1,039 crack users in the three largest Dutch cities were analyzed to explore their role in the crack market as buyers and sellers. Of the total number of users, 42.3% bought crack in public places, 39.6% through home delivery, and 13.9% at dealer’s addresses. Near one-third reported participating in selling drugs, defining themselves as “go-betweens” (21.4%) or “dealers” (9.2%). User-sellers and nonselling users did not differ with regard to gender and ethnicity. Cluster analysis resulted in three distinct types of user-sellers (freelancers, assistants, and amateurs), each characterized by time spent selling drugs, type of drugs sold, and earnings. Amateurs seem quite similar to what scholars have labeled “social dealers” in recreational drugs markets. This study suggests the need for a more differentiated law enforcement policy toward drug-selling 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. Criterion validity was tested against the Composite International Diagnostic Interview (CIDI) 3.0 DSM-IV diagnosis cannabis dependence, and psychometric properties were assessed separately for males and females and for ethnic subgroups. Principal component analysis showed that all items of the scale loaded on a single factor and reliability of the SDS total score was good (Cronbach's α = 0.70). However, criterion validity against the CIDI diagnosis cannabis dependence was low: area under curve (AUC) was 0.68 (95% confidence interval: 0.64-0.73) and at the optimal differentiating cut-off (SDS ≥ 4), sensitivity was 61.3% and specificity 63.5%. Results were similar for subgroups on gender and ethnicity. While internal consistency of the SDS is good, its use as a screener to differentiate between dependence and non-dependence within populations of young adult frequent cannabis users is not recommended.

Estimating the prevalence of crack dependence using capture-recapture with institutional and field data: a three-city study in The Netherlands

The aim of this study was to estimate the prevalence of crack dependence in the three largest Dutch cities (Amsterdam, Rotterdam, The Hague), stratified by gender and age. Three-sample capture-recapture, using data (collected between 2009 and 2011) from low threshold substitution treatment (n = 1,764), user rooms (n = 546), and a respondent-driven sample (n = 549), and applying log-linear modeling (covariates: gender, age, and city), provided a prevalence rate of 0.51% (95% CI: 0.46%-0.60%) for the population aged 15-64 years, with similar estimates for the three cities. Females (23.0% of total estimate) and younger crack users (12.8% aged <35 years) might be underrepresented in drug user treatment services.

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. Overall, cannabis use and dependence declined, including interviewees who quit using cannabis completely, in particular with students, both during their study and after they got employed. Life course theory appeared to be a useful framework to explore how and why occupational life is related to cannabis use and dependence over time. Our study showed that life events in this realm are rather common in young adults and can have a strong impact on cannabis use. While sometimes changes in use are temporary, turning points can evolve from changes in educational and employment situations; an effect that seems to be related to the consequences of these changes in terms of amount of leisure time and agency (i.e., feelings of being in control).

Differential profiles of crack users in respondent-driven and institutional samples: a three-site comparison

BACKGROUND/AIM

Respondent-driven sampling (RDS) is increasingly applied in social epidemiological surveys among 'hidden populations' of hard drug users. The objective of the present study was to assess whether the profile of frequent crack users recruited through RDS differed from those surveyed in two random institutional samples, i.e. low-threshold opiate substitution treatment (ST) and user rooms (URs).

METHODS

A total of 1,039 crack users (mean age 45.1 ± 9.1 years; 81.5% males; 49.5% non-Western ethnicity) were interviewed in three Dutch cities, using each sampling strategy in each city. Characteristics of respondents in the three samples (per city and aggregated) were compared.

RESULTS

Crack users in the RDS sample were more likely to be younger and less likely to be poorly educated, have a long crack-using career (≥10 years), use opiates and attend ST than those in both of the other samples. The RDS and UR samples showed the most differences, with more female and Western crack users in the RDS group, and UR participants were more likely to have been arrested and to have entered inpatient drug treatment in the last year.

CONCLUSION

RDS resulted in a different profile of crack users. It is a valuable methodology to achieve a more diverse representation of crack-using populations than institutional random samples.

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. Between September 2008 and April 2009, baseline data were collected from 600 frequent cannabis users with an average age of 22.1 years, predominantly male (79.3%) and an average cannabis use history of 7.1 years; 42.0% fulfilled a (12-month DSM-IV) diagnosis of cannabis dependence. The response rate was 83.7% after the first follow up at 18 months. The second and last follow-up is planned at 36 months. Computer assisted personal interviews (CAPI) were conducted which covered: cannabis use (including detailed assessments of exposure, motives for use and potency preference); use of other substances; DSM-IV internalizing and externalizing mental disorders; treatment seeking; personality; life events; social support and social functioning.

Cannabis Dependence and Peer Selection in Social Networks of Frequent Users

In a Dutch longitudinal study on the dynamics of cannabis dependence, at baseline 600 frequent cannabis users (? 3 days cannabis use per week in past 12 months) aged 18–30 years were interviewed. Nearly half of all participants (42%) met DSM-IV criteria for cannabis dependence in the 12 months prior to the interview. Participants were recruited by respondent-driven sampling; referrals were understood as proxy for social networks to explore peer associations and social exclusion. Analyses revealed that networks of frequent cannabis users were mostly heterogeneous. Cannabis dependence did not emerge as a main selector. However, within segments of networks some clustering of cannabis dependence (indicating differential inclusion), sex and ethnicity was found. Methodological questions are discussed regarding the applicability of respondent-driven sampling in noninjecting, nonmarginalized drug users. The study's limitations are noted.

Access to Licensed Cannabis Supply and the Separation of Markets Policy in the Netherlands

In the Netherlands, small amounts of cannabis can be lawfully sold to consumers in so-called coffee shops. Many communities in the country do not have coffee shops, and users under 18 years of age are not allowed to enter coffee shops. A field sample of 773 current cannabis users were interviewed in seven Dutch cities, two without any coffee shop, five varying in coffee shop density. The vast majority (n = 665; 86.0%) buy their own cannabis, and more than 70% of the cannabis is bought in licensed coffee shops. In logistic regression analyses, three variables were significantly and independently associated with buying from unlicensed suppliers: coffee shop density, age, and sex. With higher coffee shop density it was less likely to buy outside of coffee shops. Under-age buyers were more than twice as likely to buy their cannabis from unlicensed dealers. Males were more likely to buy their cannabis from unlicensed sellers than females. A substantial proportion of unlicensed suppliers sell other drugs as well, thereby increasing the risk of being offered hard drugs when buying soft drugs. This risk is greater for minors than for adults, since a higher proportion of minors use unlicensed selling points.

The role of peers in the initiation and continuation of ecstasy use

This study is a supplement to the Netherlands XTC Toxicity Study (NeXT), funded by grants from the Netherlands Organisation for Health Research and Development as part of its Addiction Programme. To better understand the processes of peer influence and peer selection, in a field study 106 Ecstasy users (67M/39F, average age 25.4 years) were interviewed face-to-face in Amsterdam in 2005. In the initiation of Ecstasy use, peer influence emerged as the dominating mechanism; peer selection was uncommon. In the continuation of Ecstasy use, peer influence and peer selection occurred reciprocally in a dynamic process, although peer influence made a greater relative contribution. Our study confirms that peer influence is a multidimensional process: influence was quite often reciprocal (with respondents both exerting and undergoing influence) and it could have both restraining and encouraging effects on ecstasy use. The study's limitations are noted.

Predicting ecstasy use among young people at risk: a prospective study of initially ecstasy-naive subjects

Our aim is to identify predictors of first-time ecstasy use in a prospective study among young people at risk. As part of the multidisciplinary Netherlands XTC Toxicity Study (NeXT), we monitored 188 subjects aged > or = 18 who were ecstasy-naive at baseline but seemed likely to start taking ecstasy in the near future. After an 11- to 26-month follow-up period, 160 respondents remained (85.1%; mean age 21.0 years, 58.1% females): 65 who took ecstasy at least once (ecstasy users) and 95 non-users. At baseline and four times during follow-up, respondents completed self-report questionnaires. Cox regression analysis was used to examine the effects of baseline respondent characteristics on incident ecstasy use. Development of peer group ecstasy use was analyzed by logistic regression. Intention to use ecstasy, low education, and current weekly cannabis use independently increased the hazard rate for first ecstasy use. Although ecstasy use among peers at baseline was not a predictor, the proportion of ecstasy users with ecstasy-using peers increased markedly during the study. Our results suggest that targeted prevention activities should focus in particular on young people who have strong intentions to take ecstasy, especially if they are also regular smokers of cannabis.

How much for a dime bag? An exploration of youth drug markets

Relatively little is known about how youth obtain marijuana and other drugs. The Drugs, Alcohol and Violence International (DAVI) study explored youthful drug markets among samples of school students, detained youth, and school dropouts (ages 14-17 years) in the greater metropolitan areas of Philadelphia, Toronto, Montreal, and Amsterdam. Students frequently reported sharing drugs, either getting them from others or giving them to others for free. Sharing was less common among the more drug-involved detainees and dropouts. Marijuana was typically obtained either outdoors or in a house or apartment. Few youth reported getting marijuana at school. In Amsterdam, where marijuana can be purchased in small quantities in coffeeshops, this was the most common place to get marijuana, even though 18 is the legal age for purchase. Alcohol was also most likely to be obtained in stores or restaurants across all the sites, even though none were of legal age except those in Amsterdam age 16 or older. Youth most often reported purchasing marijuana in nickel, dime or other small bags, which are not standardized units. The exception again was Amsterdam, where youth most often reported quantities in grams or joints, which is how it is sold in coffeeshops. The lack of standardization of units makes economic cost estimates suspect. Even standardized units such as alcohol present problems since youth report a wide range of 'typical purchases.' Survey data can, however, more aptly describe drug market characteristics such as general location of purchase, and relationship with the seller.

How to find future ecstasy-users: targeted and snowball sampling in an ethically sensitive context

This article documents the design and the sampling procedures of a prospective longitudinal multidisciplinary study on the neurotoxicity of ecstasy (MDMA): the Netherlands XTC Toxicity Study (NeXT). Targeted and snowball sampling was used to recruit 188 respondents who were ecstasy-naive at baseline. All respondents completed baseline questionnaires and underwent medical and neuropsychological examinations. At the end of a 11- to 26- month follow-up period in which they completed four additional questionnaires, 160 respondents remained (85.1%). A total of 65 participants (40.6%) took ecstasy for the first time during the follow-up period. This paper discusses the ethical dilemmas inherent in a study of this type and the specific problems and solutions that emerged in the sampling. The sampling was tightly constrained by our need to locate respondents who were potential future ecstasy users while also meeting strict medical and technical criteria. The 'intention to use' criterion proved to be a clear-cut inclusion rule that was practical to apply in the fieldwork.

Cognition in novice ecstasy users with minimal exposure to other drugs: a prospective cohort study

CONTEXT

Ecstasy (street name for [+/-]-3,4-methylenedioxymethamphetamine [MDMA]) use has been associated with cognitive deficits, especially in verbal memory. However, owing to the cross-sectional and retrospective nature of currently available studies, questions remain regarding the causal direction and clinical relevance of these findings.

OBJECTIVE

To examine the relationship between Ecstasy use and subsequent cognitive performance.

DESIGN

A prospective cohort study in Ecstasy-naive subjects with a high risk for future first Ecstasy use, as part of the Netherlands XTC Toxicity study. The initial examination took place between April 10, 2002, and April 28, 2004; follow-up was within 3 years after the initial examination.

SETTING AND PARTICIPANTS

One hundred eighty-eight healthy Ecstasy-naive volunteers (mean age, 22 years) were recruited. Of these, 58 subjects started using Ecstasy (mean cumulative dose, 3.2 tablets; median cumulative dose, 1.5 tablets). They were compared with 60 persistent Ecstasy-naive subjects matched on age, sex, intelligence, and use of substances other than Ecstasy. Differences in cognition between Ecstasy users and Ecstasy-naive subjects were adjusted for differences in cannabis and other recreational drug use.

MAIN OUTCOME MEASURES

Change scores between the initial examination and follow-up on neurocognitive tests measuring attention, working memory, verbal and visual memory, and visuospatial ability.

RESULTS

At the initial examination, there were no statistically significant differences in any of the neuropsychological test scores between persistent Ecstasy-naive subjects and future Ecstasy users. However, at follow-up, change scores on immediate and delayed verbal recall and verbal recognition were significantly lower in the group of incident Ecstasy users compared with persistent Ecstasy-naive subjects. There were no significant differences on other test scores.

CONCLUSIONS

Our findings suggest that even a first low cumulative dose of Ecstasy is associated with decline in verbal memory. Although the performance of the group of incident Ecstasy users is still within the normal range and the immediate clinical relevance of the observed deficits is limited, long-term negative consequences cannot be excluded.

Differential responses to cannabis potency: A typology of users based on self-reported consumption behaviour

AIMS

To determine whether a classification of cannabis users into different types can help to clarify the relationship between cannabis potency and consumption behaviour, harmful physical effects and psychological dependency.

METHODS

A field sample of 388 respondents was recruited who had smoked cannabis at least once in the past month. They were contacted and interviewed in 28 cannabis coffee shops located in five Dutch cities. Data were collected with an assisted self-completion questionnaire. Cluster analysis was performed using the k-means method.

FINDINGS

Various ways were observed in which cannabis users in natural settings adjusted their intake to the potency of the drug. Cluster analysis identified three broad types of cannabis users. The strongest high type was the youngest, consumed the highest monthly dose, inhaled higher-potency cannabis more deeply, and scored highest on psychological cannabis dependency. The consistent high type preferred milder cannabis, consumed the lowest monthly dose, and compensated for stronger cannabis by inhaling less deeply and smoking less. The steady quantity type was the oldest, usually smoked alone, consumed an intermediate monthly dose, and did not tend to adjust the depth of inhalation to the potency of the cannabis. The results suggest that this typology might also reflect three successive stages in the careers of continuing cannabis users.

CONCLUSIONS

Laboratory studies to assess the effects of higher THC concentrations on external and internal exposure to cannabis should allow for the possibility that the types of users studied can affect the results.

The Netherlands XTC Toxicity (NeXT) study: objectives and methods of a study investigating causality, course, and clinical relevance

This paper describes the objectives and methods of The Netherlands XTC Toxicity (NeXT) study focussing on the causality, course, and clinical relevance of ecstasy neurotoxicity. Previous studies suggest that ecstasy (3,4 methylene-dioxymethamphetamine, MDMA, XTC) is toxic toward brain serotonin axons, but most of these studies have serious methodological limitations. The current study is a combination of different approaches with three substudies: (1) a crosssectional substudy among heavy ecstasy users and controls with variation in drug use, which will provide information about potential neurotoxic consequences of ecstasy in relation to other drugs; (2) a prospective cohort substudy in ecstasy-naive subjects with high risk for future ecstasy use, which will provide information on the causality and short-term course of ecstasy use and potential neurotoxicity, and (3) a retrospective cohort substudy in lifetime ecstasy users and matched controls of an existing epidemiological sample that will provide information on long-term course and outcome of ecstasy use in the general population. Neurotoxicity is studied using (a) different imaging techniques (beta-CIT SPECT, 1H-MR spectroscopy, diffusion tensor imaging, perfusion weighted imaging and functional magnetic resonance imaging), and (b) neuropsychological and psychiatric assessments of memory, depression, and personality. The combined results will lead to conclusions that can be used in prevention messages, clinical decision making, and the development of an (inter)national ecstasy policy.

Dutch coffee shops and trends in cannabis use

Conflicting predictions have been made to the influence of decriminalization on cannabis use. Prohibitionists forecast that decriminalization will lead to an increase in consumption of cannabis, while their opponents hypothesise that cannabis use will decline after decriminalization. Most probably cannabis use in the Netherlands so far evolved in two waves, with a first peak around 1970, a low during the late 1970s and early 1980s, and a second peak in the mid-1990s. It is striking that this trend in cannabis use among youth in the Netherlands rather parallels four identified stages in the availability of cannabis. The number of cannabis users peaked when the cannabis was distributed through an underground market (late 1960s and early 1970s). Then the number decreased as house dealers were superseeding the underground market (1970s), and went up again after coffee shops took over the sale of cannabis (1980s), and stabilised or slightly decreased by the end of the 1990s when the number of coffee shops was reduced. Although changes in cannabis policy went along with changes in availability of cannabis and prevalence of cannabis use, it is questionable whether changes in cannabis policy were causally related to trends in cannabis use. Cannabis use also developed in waves in other European countries that did not decriminalize cannabis, as well as in the US. Consequently, trends in cannabis use seem to develop rather independently of cannabis policy.

Windmills in Their Minds? Drug Policy and Drug Research in the Netherlands

Contemporary Dutch drug policy is a product of many long-term political, demographic and social changes that have taken place in the Netherlands since the nation's first drug law was enacted in 1919. Shifts in policy emphasis are described and explained in terms of three principles that serve as the cornerstones of the Dutch approach, these include the following: (1) a separation of the markets for hard and soft drugs; (2) normalization of the phenomenon, which means treating drug users as ordinary citizens entitled to government assistance, but also required to assume responsibility for their actions; and (3) harm reduction efforts directed at minimizing the damage done by drugs to users, communities and to the society as a whole. The changing policies regarding cannabis are utilized here as a case study to illustrate how these principles work in practice. Several contemporary issues are analyzed in terms of their influence on recent policy changes. These include drug-related nuisance, the participation of organized crime in drug markets and criticism from abroad regarding the impact of Dutch policies on other nations. The article concludes with a reconsideration of the effects of decriminalizing cannabis, contrasting the Dutch application of the expediency principle with its use in other nations.

Cocaine and Crack in Amsterdam: Diverging Subcultures

Recreational cocaine use spread rapidly in Amsterdam at the end of the 1970s, particularly as a “party drug” in clubs and discotheques. At the end of the 1980s, the role of cocaine as party drug was largely taken over by ecstasy. In contrast, first cocaine and then crack cocaine increased in popularity among heroin addicts and marginalized street youth, including homeless youth and young prostitutes. Today, experimental use of crack is also observed among young people from socially deprived neighborhoods, especially among ethnic minorities. This article describes, mainly on the basis of ethnographic studies among these groups, the evolving and diverging patterns of use among trendsetting party youth and their marginalized counterparts. Important differences may be observed between groups related to socio-economic background, the role cocaine plays in their lives, transmission routes, and different operating market mechanisms influenced by drug policy. For party youth, cocaine use mainly serves recreational purposes. In contrast, for problem youth, cocaine, and now especially crack, contribute to multi-problem behavior within the context of their marginalized lifestyles.

Estimating the number of heroin users: a review of methods and empirical findings from The Netherlands

This article reviews major methods applied to estimate the number of heroin users in a community, predominantly urban areas. The main focus is on applicability of methods to the available data. Methodologies are evaluated with regard to reliability, validity, and feasibility from the perspective of empirical findings, in particular in the Netherlands. Findings from Amsterdam and Rotterdam are presented in more detail in order to discuss major criteria for application of the capture/recapture and the nomination techniques.