University of Amsterdam
Bonger IInstitute of Criminology
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... more
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.
- by Annemieke Benschop and +3
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- Marketing, Pragmatics, Adolescent, Quebec
The purpose of this study was to describe delinquent girls' weapons preferences and where and how often they carried weapons and to identify the most important factors that explained four different weapon-related violent outcomes. A... more
The purpose of this study was to describe delinquent girls' weapons preferences and where and how often they carried weapons and to identify the most important factors that explained four different weapon-related violent outcomes. A large, high-risk sample of female adolescents consisting of 510 girls aged 14-17 in four cities were interviewed using the same questionnaire and methods. Tabular and logistic regression analyses were applied. Knives emerged as the most frequently reported weapon in all cities. Rates of both lifetime victimization and perpetration of violence with weapons were high in all sites. Starting to carry a weapon as a result of violence was reported by 40% of the girls in Toronto, 28% in Philadelphia, 25% in Amsterdam, and 16% in Montreal. The major predictors of weapon perpetrated violent behaviours included ethnic origin, early onset of delinquent activities, participation in delinquent acts in the past 12 months, gang fighting and carrying a weapon as a result of violence. Site, age and heavy alcohol consumption had a minor impact, and drug use, drug selling, and neighborhood features, none. Despite numerous differences in weapons' prevalence across cities, the logistic regression found that site was only significant in use of an object (Toronto) and not significant in threatening or hurting someone with either a knife or a gun or actually hurting others with a weapon. These findings suggest commonality in serious female violence that extends beyond borders and cultures.
Vanuit vier invalshoeken is het reilen en zeilen van Amsterdamse coffeeshops -met uitzondering van de 26 in het 1012-gebied die moeten sluiten -in kaart gebracht. Eerst is gekeken naar de directe omgeving van de coffeeshops en hoe zij er... more
Vanuit vier invalshoeken is het reilen en zeilen van Amsterdamse coffeeshops -met uitzondering van de 26 in het 1012-gebied die moeten sluiten -in kaart gebracht. Eerst is gekeken naar de directe omgeving van de coffeeshops en hoe zij er van buiten uitzien. Vervolgens zijn exploitanten van 66 coffeeshops geïnterviewd. Daarna zijn in 59 van deze coffeeshops observaties gedaan en klanten geteld. Tegelijkertijd zijn in deze coffeeshops 1214 klanten geïnterviewd.
- by Dirk Korf
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Factor analysis of the MMM confirmed a 5-factor structure.
- by Dirk Korf and +1
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- Psychology, Psychometrics, Adolescent, Boredom
The aim of this study was to examine the perceptions of homeless youth of the care they receive. Since we wanted to involve homeless youth as participants in this project, we adopted the approach of peer-research. This form of... more
The aim of this study was to examine the perceptions of homeless youth of the care they receive. Since we wanted to involve homeless youth as participants in this project, we adopted the approach of peer-research. This form of collaborative research has a major role for homeless youth in making an inventory of the problems. A parallel is drawn between the parent-adolescent relationship and the relationship between social worker and homeless adolescent.
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. A field sample of... more
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. 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. 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, a...
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... more
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.
- by Peggy Van Der Pol and +2
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- Addiction, Prospective studies, Young Adult, Netherlands
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... more
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.
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)... more
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.
- by Peggy Van Der Pol and +2
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- Design, Social Support, Adolescent, Young Adult
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... more
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.
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... more
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).
- by Peggy Van Der Pol and +2
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To examine the course and the predictors of the persistence of cannabis dependence. Through cannabis outlets and chain referral, a prospective enriched community cohort of 207 young adults (aged 18-30) with DSM-IV cannabis dependence at... more
To examine the course and the predictors of the persistence of cannabis dependence. 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). Four groups were distinguished: persistent dependent (DDD: 28.0%), stable non-persistent (DNN: 40.6%), late non-persistent (DDN: 17.9%) and recurr...
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... more
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.
Définir le travail de proximité est une tâche plus complexe qu"il ne semble au premier abord. Les activités de proximité dans le domaine des drogues ayant souvent été dirigées vers les populations d"usagers de drogues "difficiles à... more
Définir le travail de proximité est une tâche plus complexe qu"il ne semble au premier abord. Les activités de proximité dans le domaine des drogues ayant souvent été dirigées vers les populations d"usagers de drogues "difficiles à atteindre" ou "cachées", qui ne sont pas touchées par les services de soins existants pour toxicomanes, on peut en déduire : qu"il existe des populations cachées d"usagers de drogues qui n"ont pas accès aux services pour toxicomanes ; que contacter ces populations difficiles à atteindre pourrait résoudre certains problèmes. Ces populations ne demandent pas directement le contact, bien que l"expérience montre que les usagers de drogues souhaitent le contact s"il est fait de manière compatible avec leurs modes de vie (Rhodes et al ., 1991a). Ce qui caractéristique de façon spécifique le travail de proximité est que les professionnels, les pairs ou les bénévoles prennent contact avec les usagers de drogues principalement dans leur milieu natureldans la rue, chez eux ou dans tout autre endroit où ils se trouvent. Ce point est également au centre de la définition du travail de proximité, proposée par Hartnoll et al. (1990) : Une activité dirigée vers les communautés locales, qui vise à entrer en contact avec des personnes ou des groupes issus de populations particulièrement ciblées qui ne sont pas efficacement contactés ou atteints par les services existants ou par les circuits traditionnels d'éducation pour la santé. Cette définition révèle les origines du travail de proximité. Contacter activement les usagers "là-bas" a été l"une des réponses qui a permis de prendre conscience des limites et des contraintes des services existants, plus conventionnels, destinés aux usagers de drogues. Ce n"est cependant pas toujours une tâche facile. En plus de beaucoup d"autres critiques, les activités de proximité ont été ressenties comme une menace à l"égard des services de soins existants pour les usagers de drogues. (Jacob, 1997). La définition de Hartnoll et al. montre aussi clairement, par omission, que le travail de proximité ne se réfère à aucune méthode de travail spécifique, ni à aucun type spécifique d"organisme ou d"intervenant. Il peut répondre à des objectifs variés, et des formes d"activités très différentes se reconnaissent sous cette appellation. Cette diversité est aussi la caractéristique du travail de proximité et cela explique pourquoi il est si difficile de l"identifier ou de le définir. Le travail de proximité prend des formes diverses (Stimson et al., 1994 ; Rhodes, 1994b), dont le travail de rue et le travail en institutions, souvent cités car ils sont les plus pratiqués, bien que la répartition de ces différentes formes de travail varie d"un projet à l"autre. Le travail de rue, souvent dirigé vers des personnes ou des groupes, se fait en dehors du cadre d"un local, avec une équipe qui travaille là où sont les usagers, par exemple dans les rues, les cafés, les gares et les squats. On peut également identifier des formes de travail de proximité proposant des services au domicile des usagers, lorsque les intervenants travaillent directement chez les personnes, tout comme on peut en trouver des formes dans le développement local, lorsque le travail des intervenants s"effectue directement à ce niveau. Le travail en institutions est dirigé davantage vers des organismes que vers des personnes, les équipes de proximité travaillant dans des associations et des institutions locales comme les prisons, les lieux d"hébergement, les clubs de jeunes et les écoles. En plus du contact avec les usagers individuels de ces lieux, leur objectif est de diffuser une information sur les problèmes de drogues et sur les services mis à leur disposition et auxquels ils peuvent s"adresser. Le travail de rue semble être la forme la plus courante en Europe, même s"il est encore peu pratiqué dans certains pays. Dans la plupart des pays, le travail en institutions et au domicile des usagers est rare (voir Tableau 1, ci-dessous). On peut cependant se demander si la définition de Hartnoll et al., qui donne une explication générale du travail de proximité, est adaptée aux formes plus récentes de ce travail dirigées vers les drogues de synthèse et dans les "raves". Mais en ce qui concerne les drogues "classiques", cette définition recouvre largement le travail de proximité.
- by Dirk Korf
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The aim of this paper is to assess the influence of coffee shop availability on the prevalence and intensity of cannabis use, as well as the effectiveness of the ‘separation of markets’ policy. A convenience sample of nightlife visitors... more
The aim of this paper is to assess the influence of coffee shop availability on the prevalence and intensity of cannabis use, as well as the effectiveness of the ‘separation of markets’ policy. A convenience sample of nightlife visitors and a sub-selection of previous year cannabis users were used for analyses on cannabis and hard drugs use. Logistic regression analyses showed that coffee shop proximity does not seem to be linked to prevalence of cannabis use or intensity of use. In addition, proximity of coffee shops does not seem to be linked directly to hard drugs use.
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... more
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.