Leon Knoops & Sjef Pelsser

Mainline chemsex team

Leon Knoops

Leon is outreach worker, researcher and trainer at Mainline Foundation since 2006. He has done research into drug use among Amsterdam gay and bisexual men ever since 2010.

Leon is co-writer of the status report ‘Tina and Slamming; MSM, crystal meth use end injecting drugs in a sexual setting’ and the recent website about crystal meth: sexntina.nl. He also offers chemsex training to professionals working in addiction – and healthcare. Initiated the Amsterdam Chemsex Roundtable, in which Amsterdam based organizations get together twice a year to deliberate on what’s going on regarding chemsex.

Co-organizer and host of fortnightly meetings for gay men using drugs during sex, as well as for those who no longer use drugs. Coaching men who want to quit with drug use during sex. Always on the lookout for ways to facilitate approachable means for users to find information and advice on chemsex and underlying issues.

Sjef Pelsser

Sjef is chemsex veteran and used crystal meth for three years and quit with chemsex in 2015. He decided to use his own experience within the worldwide chemsex scene, as a source to talk openly without prejudice about drugs and sex.

Got and took the opportunity to become part of Mainline’s chemsex team. Online fieldwork on gay dating sites, next to taking part in chemsex training/workshops for professionals in health and addiction care, are just a few of his activities.

Sjef believes it to be of the utmost importance that chemsex veterans should be involved as much as possible in creating (harm reduction) interventions for users whether or not they consider themselves to be problematic users. Talking with, listening to and understanding them and, if needed, giving suggestions out of personal experience. This all in a non-judgemental way.


Problematic chemsex: from signals to harm reduction interventions. Problematic chemsex, reportedly on the increase in cities with a large MSM population, is a result of intersecting factors including gay history, adverse childhood experiences and HIV/AIDS, often leading to loneliness and depression.

Mainline, a Dutch foundation, has been developing successful interventions for gay men participating in problematic chemsex since 2016. This short presentation will explore and evaluate harm reduction strategies and interventions that have worked for this specific target group.

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We are excited to announce that Haven Wheelock will be a HIT Hot Topics speaker. Haven was a Chief Petitioner for ballot measure 110, which was a first in the USA initiative to decriminalise drugs in the state of Oregon. 2022.hit.org.uk/haven-wheelock/ #harmreduction #conference


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