Dirk Korf | University of Amsterdam (original) (raw)

Papers by Dirk Korf

Cahier De reeks Cahier omvat de rapporten van onderzoek dat door en in opdracht van het WODC is v... more Cahier De reeks Cahier omvat de rapporten van onderzoek dat door en in opdracht van het WODC is verricht. Opname in de reeks betekent niet dat de inhoud van de rapporten het standpunt van de Minister van Veiligheid en Justitie weergeeft. Alle WODC-publicaties zijn gratis te downloaden van www.wodc.nl. Wetenschappelijk Onderzoek-en Documentatiecentrum Cahier 2013-1 | 3 Inhoud Samenvatting en conclusies-7 1 Inleiding-15 1.1 Aanleiding tot het onderzoek: twee nieuwe gedoogcriteria-15 1.2 Doel en onderzoeksvragen-18 1.3 Leeswijzer-19 2 Methode van onderzoek-21 2.1 Opzet van het onderzoek-21 2.2 'Theory-driven' aanpak-22 2.3 De steekproef-23 2.4 Het verloop van de implementatie: de procesevaluatie-25 2.5 De meting van uitkomsten-27 3 Coffeeshops: ontstaan en beleid-29 3.1 De oorsprong van de coffeeshops-29 3.2 'Hard' gedogen van coffeeshops-31 3.3 Problemen en beleidsreacties (in vogelvlucht)-32 3.4 Lokaal en regionaal beleid-34 3.5 Zelfregulering door de coffeeshops-37 3.6 Coffeeshops en de volksgezondheid-38 3.7 Samenvatting-39 4 De situatie rond coffeeshops tijdens de aanloop naar de B-en I-criteria-41 4.1 Aantal coffeeshops in Nederland-41 4.2 Coffeeshopbezoeken en drugstoeristen-42 Bezoeken en bezoekers-42 4.2.1 Drugstoeristen-43 4.2.2 4.3 Klanten van coffeeshops-44 4.4 Overlast rond coffeeshops-45 4.5 Georganiseerde (drugs)criminaliteit-47 4.6 Samenvatting-48 5 Het Besloten club-en het Ingezetenencriterium uiteengerafeld: de interventielogica achter de criteria-49 5.1 De problematiek zoals verondersteld in de interventielogica-50 5.2 De wettelijke-en beleidscontext van de B-en I-criteria-52 5.3 De beoogde uitvoering-54 De landelijke overheid/ministerie van VenJ-54 5.3.1 College van procureurs-generaal/Parket-Generaal Openbaar 5.3.2 Ministerie-56 Het lokaal bestuur/de burgemeester-57 5.3.3 De arrondissementsparketten van het Openbaar Ministerie-60 5.3.4 De politie-61 5.3.5 De lokale driehoek-63 5.3.6 De coffeeshophouders-64 5.3.7 De coffeeshopklanten-66 5.3.8 5.4 De beoogde uitkomsten en te bestrijden neveneffecten-67 4 | Cahier 2013-2 Wetenschappelijk Onderzoek-en Documentatiecentrum 5.5 De landelijke interventielogica in samenhang-69 5.6 Formele taken, verantwoordelijkheden en bevoegdheden in het coffeeshopbeleid-69 5.7 De uitvoering van de B-en I-criteria: een complex proces-71 6 De problematiek volgens de betrokken actoren-73 7 De implementatie van de B-en I-criteria volgens de betrokken actoren: resultaten van de procesevaluatie-77 7.1 Inleiding-77 7.2 Actoren in actie-77 De landelijke overheid/ministerie van VenJ-77 7.2.1 College van procureurs-generaal/Parket-Generaal Openbaar 7.2.2 Ministerie-82 Het lokaal bestuur/de burgemeester-84 7.2.3 De arrondissementsparketten van het Openbaar Ministerie-91

Verslaving, 2005

(Eds.) (2004), European studies on drugs and drug policy. Brussel: VUB Brussels University Press,... more (Eds.) (2004), European studies on drugs and drug policy. Brussel: VUB Brussels University Press, 220 p. Dit is een opmerkelijk boek. Handelingen van wetenschappelijke bijeenkomsten waren vroeger een gebruikelijk communicatiemedium om de achterblijvers te informeren over de jongste inzichten. Tegenwoordig worden ze nauwelijks meer gedrukt, omdat er aan vaktijdschriften geen gebrek is, en internet iemand sneller van dienst is dan welke drukpers ook. Toch gaat het bij dit boek om 'proceedings', om handelingen in de klassieke zin. En ook eigenlijk weer niet. De uitgave bevat slechts tien van de 36 bijdragen aan de veertiende internationale conferentie van de European Society for Social Drug Research (ESSD), die in oktober 2003 in Gent werd gehouden. Dertien lezingen werden voor opname in het boek aangeboden; drie daarvan wezen de redacteuren af. Een aftelsom leert dat 23 lezingen voor publicatie in deze uitgave buiten beschouwing zijn gebleven. Waarom, dat vertellen de redacteuren niet. Het zou het resultaat geweest kunnen zijn van strenge voorselectie om een coherent boek te kunnen overhouden. Maar waarschijnlijker is dat de meeste onderzoekers niet de moeite wilden nemen hun voordracht voor een boek te bewerken. Daarom blijft het onduidelijk of de ondertitel van de uitgave-'selected readings'-terecht is. Coherent is het boek niet geworden. Een minderheid van de hoofdstukken concentreert zich op (beschrijvende) cijfers; de meerderheid bevat bespiegelingen met een sausje wetenschap. Een rode draad ontbreekt. Ee´n hoofdstuk gaat over heroı¨ne, twee over cannabis (in Denemarken en Zwitserland), e´e´n over ecstasy in

Dit rapport heeft als doel:Een inventarisatie maken van het aantal problematische GHB-gebruikers ... more Dit rapport heeft als doel:Een inventarisatie maken van het aantal problematische GHB-gebruikers dat in aanraking komt met politie en justitie en wordt ingesloten of (op medische gronden) wordt heengezonden.Inzicht verschaffen in de kenmerken van problematische GHB-gebruikers, en de aard van de problematiek.Aanknopingspunten bieden voor de aanpak van de problematiek.

Het onderhavige onderzoek is in de WODC onderzoeksprogrammering opgenomen als deel I van het onde... more Het onderhavige onderzoek is in de WODC onderzoeksprogrammering opgenomen als deel I van het onderzoek naar de ‘hedendaagse jeugdcriminaliteit en het dark number jeugdcriminaliteit’. Naast dit onderzoek wordt (separaat) nog een tweede onderzoek uitgevoerd, deel II (project 2034). Dit onderzoek behelst een koppeling van gegevens uit de Monitor Zelfgerapporteerde Jeugdcriminaliteit (MZJ) - waarin ruim 3.000 jongeren zijn bevraagd over delicten die ze hebben gepleegd - aan gegevens van het CBS, waaronder politieregistraties. De probleemstelling van dit onderzoek luidt: Welke concrete handelingen - binnen de delictscategorieen openbare ordedelicten en geweldsdelicten - plegen jeugdigen? Zijn dat andere handelingen dan tien jaar geleden? Worden vergelijkbare incidenten nu anders gekwalificeerd en/of bestraft dan tien jaar geleden?

In the Netherlands, the number of cocaine traffickers arrested at Schiphol International Airport ... more In the Netherlands, the number of cocaine traffickers arrested at Schiphol International Airport peaked in 2003. In May 2003, sentencing guidelines regarding cocaine traffickers were redefined into a smaller number of categories (wider quantity ranges, less specified offender categories) with lower sentences than before. New guidelines allowed criminal courts more flexibility, and judges were expected to sentence cocaine traffickers more often than before in accordance with guidelines. All cases, at all four applicable criminal courts, against cocaine traffickers that had been arrested at Schiphol in 2003 were analyzed (877 simple court and 994 full court cases). In between 30 and 40 percent of cases sentences were not according to the guidelines (mostly lower), and even more frequently than before the new guidelines had been introduced. Experience as a judge (number of years) was not associated with keeping up with guidelines, but male judges sentenced suspects more often than fema...

European addiction research, Jan 28, 2015

To examine the course and the predictors of the persistence of cannabis dependence. Through canna... 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...

Addiction, 2014

Increased delta-9-tetrahydrocannabinol (THC) concentrations in cannabis may lead to higher THC ex... 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.

Drug and Alcohol Dependence, 2013

Background: Frequent cannabis users are at high risk of dependence, still most (near) daily users... 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.

Life course theory considers events in study and work as potential turning points in deviance, in... 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).

International Journal of Methods in Psychiatric Research, 2011

This paper presents an overview of the prospective cohort design of the Dutch Cannabis Dependence... 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.

International Journal of Methods in Psychiatric Research, 2013

The Severity of Dependence Scale (SDS) measures with five items the degree of psychological depen... 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.

Addiction, 2013

To compare the prevalence of mental disorders between frequent cannabis users with and without de... more To compare the prevalence of mental disorders between frequent cannabis users with and without dependence and the general population. Cross-sectional comparison of interview data. Enriched community sample of frequent cannabis users and a representative sample of non-users and non-frequent users from the general population. 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. 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. 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. 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.

The International journal on drug policy, 2007

To determine whether a classification of cannabis users into different types can help to clarify ... 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...

The International journal on drug policy, 2015

The link between leisure and cannabis use has been widely studied, but less so for young adults, ... more 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. 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. 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 dif...

Adolescence, 2008

The aim of this study was to examine the perceptions of homeless youth of the care they receive. ... 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.

Addictive Behaviors, 2015

Factor analysis of the MMM confirmed a 5-factor structure.

Vanuit vier invalshoeken is het reilen en zeilen van Amsterdamse coffeeshops -met uitzondering va... 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.

International Journal of Drug Policy, 2014

Victims & Offenders, 2011

Concerns over youth violence and victimization are widespread, but it is rare that national trend... more Concerns over youth violence and victimization are widespread, but it is rare that national trends can be compared with identical methods. This paper provides a cross-national examination of internalized, externalized, and help-seeking responses to weapon-related victimization among 1,398 at-risk male and female youth between the ages of 14 and 17 in Toronto, Montreal, Philadelphia, and Amsterdam. Analyses were conducted of

Journal of Urban Health, 2006

The purpose of this study was to describe delinquent girls' weapons preferences and where and how... 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.

Cahier De reeks Cahier omvat de rapporten van onderzoek dat door en in opdracht van het WODC is v... more Cahier De reeks Cahier omvat de rapporten van onderzoek dat door en in opdracht van het WODC is verricht. Opname in de reeks betekent niet dat de inhoud van de rapporten het standpunt van de Minister van Veiligheid en Justitie weergeeft. Alle WODC-publicaties zijn gratis te downloaden van www.wodc.nl. Wetenschappelijk Onderzoek-en Documentatiecentrum Cahier 2013-1 | 3 Inhoud Samenvatting en conclusies-7 1 Inleiding-15 1.1 Aanleiding tot het onderzoek: twee nieuwe gedoogcriteria-15 1.2 Doel en onderzoeksvragen-18 1.3 Leeswijzer-19 2 Methode van onderzoek-21 2.1 Opzet van het onderzoek-21 2.2 'Theory-driven' aanpak-22 2.3 De steekproef-23 2.4 Het verloop van de implementatie: de procesevaluatie-25 2.5 De meting van uitkomsten-27 3 Coffeeshops: ontstaan en beleid-29 3.1 De oorsprong van de coffeeshops-29 3.2 'Hard' gedogen van coffeeshops-31 3.3 Problemen en beleidsreacties (in vogelvlucht)-32 3.4 Lokaal en regionaal beleid-34 3.5 Zelfregulering door de coffeeshops-37 3.6 Coffeeshops en de volksgezondheid-38 3.7 Samenvatting-39 4 De situatie rond coffeeshops tijdens de aanloop naar de B-en I-criteria-41 4.1 Aantal coffeeshops in Nederland-41 4.2 Coffeeshopbezoeken en drugstoeristen-42 Bezoeken en bezoekers-42 4.2.1 Drugstoeristen-43 4.2.2 4.3 Klanten van coffeeshops-44 4.4 Overlast rond coffeeshops-45 4.5 Georganiseerde (drugs)criminaliteit-47 4.6 Samenvatting-48 5 Het Besloten club-en het Ingezetenencriterium uiteengerafeld: de interventielogica achter de criteria-49 5.1 De problematiek zoals verondersteld in de interventielogica-50 5.2 De wettelijke-en beleidscontext van de B-en I-criteria-52 5.3 De beoogde uitvoering-54 De landelijke overheid/ministerie van VenJ-54 5.3.1 College van procureurs-generaal/Parket-Generaal Openbaar 5.3.2 Ministerie-56 Het lokaal bestuur/de burgemeester-57 5.3.3 De arrondissementsparketten van het Openbaar Ministerie-60 5.3.4 De politie-61 5.3.5 De lokale driehoek-63 5.3.6 De coffeeshophouders-64 5.3.7 De coffeeshopklanten-66 5.3.8 5.4 De beoogde uitkomsten en te bestrijden neveneffecten-67 4 | Cahier 2013-2 Wetenschappelijk Onderzoek-en Documentatiecentrum 5.5 De landelijke interventielogica in samenhang-69 5.6 Formele taken, verantwoordelijkheden en bevoegdheden in het coffeeshopbeleid-69 5.7 De uitvoering van de B-en I-criteria: een complex proces-71 6 De problematiek volgens de betrokken actoren-73 7 De implementatie van de B-en I-criteria volgens de betrokken actoren: resultaten van de procesevaluatie-77 7.1 Inleiding-77 7.2 Actoren in actie-77 De landelijke overheid/ministerie van VenJ-77 7.2.1 College van procureurs-generaal/Parket-Generaal Openbaar 7.2.2 Ministerie-82 Het lokaal bestuur/de burgemeester-84 7.2.3 De arrondissementsparketten van het Openbaar Ministerie-91

Verslaving, 2005

(Eds.) (2004), European studies on drugs and drug policy. Brussel: VUB Brussels University Press,... more (Eds.) (2004), European studies on drugs and drug policy. Brussel: VUB Brussels University Press, 220 p. Dit is een opmerkelijk boek. Handelingen van wetenschappelijke bijeenkomsten waren vroeger een gebruikelijk communicatiemedium om de achterblijvers te informeren over de jongste inzichten. Tegenwoordig worden ze nauwelijks meer gedrukt, omdat er aan vaktijdschriften geen gebrek is, en internet iemand sneller van dienst is dan welke drukpers ook. Toch gaat het bij dit boek om 'proceedings', om handelingen in de klassieke zin. En ook eigenlijk weer niet. De uitgave bevat slechts tien van de 36 bijdragen aan de veertiende internationale conferentie van de European Society for Social Drug Research (ESSD), die in oktober 2003 in Gent werd gehouden. Dertien lezingen werden voor opname in het boek aangeboden; drie daarvan wezen de redacteuren af. Een aftelsom leert dat 23 lezingen voor publicatie in deze uitgave buiten beschouwing zijn gebleven. Waarom, dat vertellen de redacteuren niet. Het zou het resultaat geweest kunnen zijn van strenge voorselectie om een coherent boek te kunnen overhouden. Maar waarschijnlijker is dat de meeste onderzoekers niet de moeite wilden nemen hun voordracht voor een boek te bewerken. Daarom blijft het onduidelijk of de ondertitel van de uitgave-'selected readings'-terecht is. Coherent is het boek niet geworden. Een minderheid van de hoofdstukken concentreert zich op (beschrijvende) cijfers; de meerderheid bevat bespiegelingen met een sausje wetenschap. Een rode draad ontbreekt. Ee´n hoofdstuk gaat over heroı¨ne, twee over cannabis (in Denemarken en Zwitserland), e´e´n over ecstasy in

Dit rapport heeft als doel:Een inventarisatie maken van het aantal problematische GHB-gebruikers ... more Dit rapport heeft als doel:Een inventarisatie maken van het aantal problematische GHB-gebruikers dat in aanraking komt met politie en justitie en wordt ingesloten of (op medische gronden) wordt heengezonden.Inzicht verschaffen in de kenmerken van problematische GHB-gebruikers, en de aard van de problematiek.Aanknopingspunten bieden voor de aanpak van de problematiek.

Het onderhavige onderzoek is in de WODC onderzoeksprogrammering opgenomen als deel I van het onde... more Het onderhavige onderzoek is in de WODC onderzoeksprogrammering opgenomen als deel I van het onderzoek naar de ‘hedendaagse jeugdcriminaliteit en het dark number jeugdcriminaliteit’. Naast dit onderzoek wordt (separaat) nog een tweede onderzoek uitgevoerd, deel II (project 2034). Dit onderzoek behelst een koppeling van gegevens uit de Monitor Zelfgerapporteerde Jeugdcriminaliteit (MZJ) - waarin ruim 3.000 jongeren zijn bevraagd over delicten die ze hebben gepleegd - aan gegevens van het CBS, waaronder politieregistraties. De probleemstelling van dit onderzoek luidt: Welke concrete handelingen - binnen de delictscategorieen openbare ordedelicten en geweldsdelicten - plegen jeugdigen? Zijn dat andere handelingen dan tien jaar geleden? Worden vergelijkbare incidenten nu anders gekwalificeerd en/of bestraft dan tien jaar geleden?

In the Netherlands, the number of cocaine traffickers arrested at Schiphol International Airport ... more In the Netherlands, the number of cocaine traffickers arrested at Schiphol International Airport peaked in 2003. In May 2003, sentencing guidelines regarding cocaine traffickers were redefined into a smaller number of categories (wider quantity ranges, less specified offender categories) with lower sentences than before. New guidelines allowed criminal courts more flexibility, and judges were expected to sentence cocaine traffickers more often than before in accordance with guidelines. All cases, at all four applicable criminal courts, against cocaine traffickers that had been arrested at Schiphol in 2003 were analyzed (877 simple court and 994 full court cases). In between 30 and 40 percent of cases sentences were not according to the guidelines (mostly lower), and even more frequently than before the new guidelines had been introduced. Experience as a judge (number of years) was not associated with keeping up with guidelines, but male judges sentenced suspects more often than fema...

European addiction research, Jan 28, 2015

To examine the course and the predictors of the persistence of cannabis dependence. Through canna... 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...

Addiction, 2014

Increased delta-9-tetrahydrocannabinol (THC) concentrations in cannabis may lead to higher THC ex... 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.

Drug and Alcohol Dependence, 2013

Background: Frequent cannabis users are at high risk of dependence, still most (near) daily users... 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.

Life course theory considers events in study and work as potential turning points in deviance, in... 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).

International Journal of Methods in Psychiatric Research, 2011

This paper presents an overview of the prospective cohort design of the Dutch Cannabis Dependence... 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.

International Journal of Methods in Psychiatric Research, 2013

The Severity of Dependence Scale (SDS) measures with five items the degree of psychological depen... 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.

Addiction, 2013

To compare the prevalence of mental disorders between frequent cannabis users with and without de... more To compare the prevalence of mental disorders between frequent cannabis users with and without dependence and the general population. Cross-sectional comparison of interview data. Enriched community sample of frequent cannabis users and a representative sample of non-users and non-frequent users from the general population. 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. 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. 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. 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.

The International journal on drug policy, 2007

To determine whether a classification of cannabis users into different types can help to clarify ... 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...

The International journal on drug policy, 2015

The link between leisure and cannabis use has been widely studied, but less so for young adults, ... more 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. 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. 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 dif...

Adolescence, 2008

The aim of this study was to examine the perceptions of homeless youth of the care they receive. ... 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.

Addictive Behaviors, 2015

Factor analysis of the MMM confirmed a 5-factor structure.

Vanuit vier invalshoeken is het reilen en zeilen van Amsterdamse coffeeshops -met uitzondering va... 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.

International Journal of Drug Policy, 2014

Victims & Offenders, 2011

Concerns over youth violence and victimization are widespread, but it is rare that national trend... more Concerns over youth violence and victimization are widespread, but it is rare that national trends can be compared with identical methods. This paper provides a cross-national examination of internalized, externalized, and help-seeking responses to weapon-related victimization among 1,398 at-risk male and female youth between the ages of 14 and 17 in Toronto, Montreal, Philadelphia, and Amsterdam. Analyses were conducted of

Journal of Urban Health, 2006

The purpose of this study was to describe delinquent girls' weapons preferences and where and how... 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.