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Short- and long-term effects of digital prevention and treatment interventions for cannabis use reduction: A systematic review and meta-analysis

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.

Cannabis Regulation in Europe: Country Report Netherlands

The Netherlands has long been considered a leader of progressive drug policy, but it is increasingly being left behind by policy innovations outside Europe. Nonetheless Dutch cities are leading the way towards more progressive and locally adapted cannabis policies. Produced as part of a the "New Approaches in Harm Reduction Policies and Practices" project, this Country Report seeks to understand the drivers of Dutch cannabis policy today, and the possibilities for its future. The project is a joint project of the Transnational Institute (TNI), based in the Netherlands ICEERS (Spain), Forum Droghe (Italy) and Diogenis (Greece).

Korf, D.J. (2019). Cannabis Regulation in Europe: Country Report Netherlands. Amsterdam: Transnational Institute.

How and Where to Find NPS Users: a Comparison of Methods in a Cross-National Survey Among Three Groups of Current Users of New Psychoactive Substances in Europe

Use of new psychoactive substances (NPS) across Europe remains a public health challenge. The study describes potentials and limitations of methods in a transnational survey of recent marginalised, nightlife and online community NPS users in Germany, Hungary, Ireland, the Netherlands, Poland and Portugal (n = 3023). In terms of demographic profile, drug use history and type of NPS, different methods reached different segments of the NPS-using population. Last year use of different NPS varied across countries and groups. Respondents used NPS in a variety of settings, with public spaces most common in the marginalised group. The study suggests that prevalence rates can reveal a picture of the NPS market that significantly deviates from what law enforcement seizures indicate. Outreach in nightlife settings and peer education are recommended to inform users about health risks and to improve access to drug services and care.

Korf, D. J., Benschop, A., Wernse, B., Kamphausen, G., Felvinczi, K., Dabrowska, K., Hernriques, S., Nabben, A. L. W. M., Wieczorek, L., Bujalski, M., Kalo, Z., Hearne, . E. & van Hout, M. C. (2019) International Journal of Mental Health and Addiction. () 1-18

Criminele samenwerkingsverbanden. Ontwikkelingen in aanpak en duiding van effectiviteit

Aanleiding voor dit onderzoek was de constatering dat de groei in het aantal aangepakte criminele samenwerkingsverbanden (csv’s) niet terug te zien was in de ontwikkeling van het aantal vrijheidsstraffen. Om de georganiseerde misdaad terug te dringen werd in 2012 tussen de (toen nog) Minister van Veiligheid en Justitie, de politie en het OM afgesproken dat er meer csv’s zouden moeten worden aangepakt: in 2014 twee keer zoveel als in 2009. Probleemstelling: Welke verklaring(en) ligt/liggen ten grondslag aan het achterblijven/ uitblijven van een stijging in het aantal strafopleggingen bij het aantal door het OM gerapporteerde aangepakte csv’s over de periode 2009-2015?

Korf, D.J., Luijk, S.J., Meijer, M.E. de (2019). Criminele samenwerkingsverbanden. Ontwikkelingen in aanpak en duiding van effectiviteit. Amsterdam: Rozenberg Publishers