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Bonger Institute of Criminology


Bonger Institute

The Bonger Institute's publications include articles in international peer- reviewed journals, book chapters and scientific reports.

[English publications and Dutch publications with English summaries are shown here.For a full overview of publications, please refer to the Dutch section of our website]

Recent publications!


Background: Frequent Cannabis use has been linked to a variety of negative mental, physical, and social consequences. We assessed the effects of digital prevention and treatment interventions on Cannabis use reduction in comparison with control conditions.

Methods: Systematic review with two separate meta-analyses. Thirty randomized controlled trials met the inclusion criteria for the review, and 21 were included in the meta-analyses. Primary outcome was self-reported Cannabis use at post-treatment and follow-up. Hedges’s g was calculated for all comparisons with non-active control. Risk of bias was examined with the Cochrane risk-of-bias tool.

Results: The systematic review included 10 prevention interventions targeting 8138 participants (aged 12 to 20) and 20 treatment interventions targeting 5195 Cannabis users (aged 16 to 40). The meta-analyses showed significantly reduced Cannabis use at post-treatment in the prevention interventions (6 studies, N = 2564, g = 0.33; 95% CI 0.13 to 0.54, p =  0.001) and in the treatment interventions (17 comparisons, N = 3813, g = 0.12; 95% CI 0.02 to 0.22, p =  0.02) as compared with controls. The effects of prevention interventions were maintained at follow-ups of up to 12 months (5 comparisons, N = 2445, g = 0.22; 95% CI 0.12 to 0.33, p <  0.001) but were no longer statistically significant for treatment interventions.

Conclusions: Digital prevention and treatment interventions showed small, significant reduction effects on Cannabis use in diverse target populations at post-treatment compared to controls. For prevention interventions, the post-treatment effects were maintained at follow-up up to 12 months later.

Boumparis, N., Loheide-Niesmann, L., Blankers, M., Ebert, D., Korf, D.J., D., Schaub, M., Spijkerman, R., Tait, R., J. and Riper, H. (2019) The short- and long-term effects of digital prevention and treatment interventions for cannabis use reduction: A systematic review and meta-analysis. Drug and Alcohol Dependence. 200, 82-94.


Evaluation Public Prosecution Service (Settlement) Act - Summary

The Public Prosecution Service (Settlement) Act (Wet OM-afdoening) provides for the imposition of a sentence in a criminal law context without court intervention by issuing a “punishment order” (strafbeschikking). The Act has been gradually phased in, starting on 1 February 2008 with the implementation of the punishment order issued by the public prosecutor (Art. 257a, Code of Criminal Procedure, Wetboek van strafvordering, Sv). In 2010, the police punishment order was introduced (art. 257b Sv) and, in 2012, the administrative punishment order (art. 257ba Sv).

The Act has been evaluated by researchers at the department of Criminal Law and the Bonger Institute of Criminology, Faculty of Law.

Abels, D., Benschop, A., Blom, T., Coster van Voorhout, J., Korf, D.J., Liebregts, N., & Vriend, K. (2018). Evaluatie Wet OM-Afdoening. Amsterdam: Rozenberg Publishers.


This exploratory study gives a picture of 4-FA users and 4-FA use. It provides insight into the user groups and the health problems that they experience resulting from their use of 4-FA. The extent to which 4-FA users consider that the substance poses a risk and the factors that play a role in their perception of this risk have been investigated. Whether the risk estimated by the users and/or the use of 4-FA has changed as a result of the recent warning campaigns and the ban on the substance has also been investigated. [DUTCH PUBLICATION WITH ENGLISH SUMMARY]

Van der Pol, P., Nijkamp, L., Nabben, T. & Van Laar, M. (2017) 4-FA. 4-Fluoramfetamine: gebruikers en gebruik in beeld. Utrecht/Amsterdam: Trimbos-instituut & Bonger Instituut voor Criminologie.

New Psychoactive Substances: transnational project on different user groups, user characteristics, extent and patterns of use, market dynamics, and best practices in prevention

The final report of the NPS-t study presents the results of a survey among over 3.000 NPS users from 6 countries. Results include patterns of use, user profiles, procurement, market dynamics, and prevention. This report highlights the variety in types of NPS users and across countries.

Benschop, A., Bujalski, M., Dabrowska, K., Demetrovics, Z., Egger, D., Felinczi, K., Henriques, S., Kalo, Z., Kamphausen, G., Korf, D.J., Nabben, T., Silva, J.P., Van Hout, M.C., Werse, B., Wells, J., Wieczorek, L. & Wouters, M. (2017). New Psychoactive Substances: transnational project on different user groups, user characteristics, extent and patterns of use, market dynamics, and best practices in prevention. NPS-transnational Project (HOME/2014/JDRU/AG/DRUG/7077).


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.

Skliamis, K. & Korf, D.J. (forth.). An Exploratory Study of Cannabis Festivals and Their Attendees in Two European Cities: Amsterdam and Berlin. Journal of Psychoactive Drugs 00(0): 1-9.

[DOI: 10.1080/02791072.2017.1380869] 


More Than Just “Pushing and Pulling”: Conceptualizing Identified Human Trafficking in the Netherlands

By tradition, the human trafficking discourse focuses on cross-border sex trafficking from impoverished countries to countries with a high standard of living. This article explores whether identified trafficking in the Netherlands corresponds to this. We introduce a model that identifies all possible trafficking situations, and with this, intends to prevent tunnel vision and identify blind spots. Subsequently, we analyze 768 trafficking cases identified by the Dutch Public Prosecution Service (2008-2012) and categorize each case according to our model: by form of exploitation and route of trafficking. The data show that (near-)domestic sex trafficking where victims are not pushed out of impoverished countries, but are recruited on native (or neighboring) soil, is the human trafficking situation most commonly identified.

Kragten-Heerdink, S.L.J., Dettmeijer-Vermeulen, C.E. & Korf, D.J. (forth.). More Than Just “Pushing and Pulling”: Conceptualizing Identified Human Trafficking in the Netherlands. Crime & Delinquency 00(0): 1-25.

[DOI: 10.1177/0011128717728503]


 Consequences of criminalisation: the Dutch khat market before and after the ban

Aims: To evaluate the consequences of criminalising khat, with a focus on the changes in law enforcement and the use, availability, price and quality of khat in the Netherlands. Methods: Mixed methods, including law enforcement data, expert interviews, focus group interviews with members of the Somali community, and a survey among 168 current (last month) khat users. Findings: Soon after the law changed (early in 2013), and khat had become an illicit drug, much of the khat imported from Africa was confiscated at Schiphol International Airport and users found it more difficult to obtain fresh khat leaves. About two years after the ban had been implemented, the price of fresh khat at user lavel had increased tenfold on average, and much of it was of poorer quality (e.g. sold in dried or powdered form). Conclusion: Criminalisation of khat in the Netherlands had substantial consequences for the distribution chain (transcontinental import by air) and there was a lach of alternative transportation routes that could supply users with fresh khat. It is highly likely that the total number of Somali khat users in the Netherlands dropped, but that the proportion of dependent and poor, "problem users" increased.

Nabben, T. & Korf, D.J. (2017) Consequences of criminalisation: the Dutch khat market before and after the ban. Drugs: Education, Prevention and Policy 24(4): 332-339.

[DOI: 10.1080/09687637.2017.1338669]


The European Society for Social Drug Research: a reflection on research trends over time

Korf, D.J., O'Gorman, A. & Werse, B. (2017) The European Society for Social Drug Research: a reflection on research trends over time. Drugs: Education, Prevention and Policy 24(4): 321-323.

[DOI: 10.1080/09687637.2017.1346061]

National Report on New Psychoactive Substances Expert Interviews in the Netherlands

In this report from the NPS-transnational team, eight experts give their view on the NPS market in the Netherlands.

Wouters, M. & Nabben, T. (2017) National Report on New Psychoactive Substances Expert Interviews in the Netherlands. NPS-transnational Project (HOME/2014/JDRU/AG/DRUG/7077).

Country report on New Psychoactive Substances in the Netherlands

This country report gives an overview of the NPS situation in terms of definitions, policy, legislation, market and prevention in the Netherlands.

Wouters, M. & Nabben, T. (2017) Country report on New Psychoactive Substances in the Netherlands. NPS-transnational Project (HOME/2014/JDRU/AG/DRUG/7077).

Antenna 2016

In Antenna 2016, trends in the Amsterdam nightlife and the related developments in substance use are described by means of a panel study among trendsetters and a survey among students in secondary vocational schools or colleges.
Tabacco, alcohol and cannabis are the substances most commonly used by vocational students, in addition to energy drinks. The use of ecstasy, cocaine, amphetamine and 4-FA is a lot less prevalent. For almost all substances holds that the older the vocational students are, the larger the group of current users.
Laughing gas is popular among varying groups of young people and young adults. In the case of the vocational students, there is hardly any difference between gender, age or ethnic background in laughing gas use.
Overall, it seems that substance use among the trendsetters is stabilizing in recent years, although with the arrival and the popularity of 4-FA and laughing gas, the drug palette has been further expanded.

Nabben, T., Luijk, S.J., Benschop, A. & Korf, D.J. (2017) Antenne 2016. Trends in alcohol, tabak en drugs bij jonge Amsterdammers. Amsterdam: Rozenberg Publishers.