Knowledge Base
Sources and notes
Every question in the Knowledge Base has a source. They are listed below per unit, with a short note. The sources are Dutch websites; the links open in a new window.
GovernmentIndependent
Unit 1
The rules in the Netherlands
- Dutch government: tolerance policy on soft drugs and coffeeshops (in Dutch)
The national conditions for coffeeshops, the 5 gram limit and what happens when the rules are broken.
rijksoverheid.nl
- Public Prosecution Service: Opium Act Instruction (Aanwijzing Opiumwet, in Dutch)
The tolerance criteria of the Public Prosecution Service, with an explanation of each letter and the role of the municipality.
wetten.overheid.nl
- Opium Act (Opiumwet, in Dutch)
The law that prohibits the possession, dealing and production of drugs in the Netherlands.
wetten.overheid.nl
- Dutch government: taking drugs abroad (in Dutch)
Why taking drugs across the border is always a criminal offence and which penalties you can get.
rijksoverheid.nl
- House of Representatives: letter on the possession of soft drugs (parliamentary paper 24077, no. 464, in Dutch)
Possession is not covered by the tolerance policy; with less than 5 grams the police confiscate it without prosecution.
zoek.officielebekendmakingen.nl
- Municipality of Haarlem: General Local By-law, APV (Article 2:74a, in Dutch)
The Haarlem rules, including the ban on open drug use in areas designated by the mayor.
lokaleregelgeving.overheid.nl
- NH Nieuws: unique quality mark for eight coffeeshops in Haarlem (5 November 2013, in Dutch)
News report on the quality mark that Haarlem introduced in 2013 as the first municipality: extra rules on top of the national tolerance rules, a Bibob integrity check and courses for staff.
nhnieuws.nl
Unit 2
Safe and mindful
- Drugs en Uitgaan (Trimbos Institute): reduce the risks of hash and weed (in Dutch)
Practical tips to make the risks smaller: take it slowly, no tobacco, wait with edible forms, do not drive, and who is advised against using.
drugsenuitgaan.nl
- Drugs Infolijn (Trimbos Institute): hash and weed, the effects (in Dutch)
How long the effects last when smoking, vaporising and eating, what drug, set and setting are, and which desired and unwanted effects there are.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): space cake, what it is and what the risks are (in Dutch)
Why edible forms work later, last longer and can be more intense, and why you never take more.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): hash and weed, the risks (in Dutch)
The risks in the short and the long term: a bad reaction, traffic, the heart, the lungs, addiction and missed chances.
drugsinfo.nl
- Dutch government: may I take part in traffic under the influence of drugs? (in Dutch)
Why driving under the influence is not allowed, how the police check and which penalties apply.
rijksoverheid.nl
- Drugs Infolijn (Trimbos Institute): what you need to know about cannabis (in Dutch)
Independent information about the effects, the risks and using cannabis safely.
drugsinfo.nl
Unit 3
What it actually is
- Drugs Infolijn (Trimbos Institute): what you need to know about cannabis (in Dutch)
Independent information about the effects, the risks and using cannabis safely.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): what is THC (in Dutch)
The substance that makes you high or stoned, the forms THC comes in, the risks and the law.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): what is CBD (in Dutch)
What CBD does and does not do, what has been proven, the risks with medicines and what is on the label.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): hash and weed, the effects (in Dutch)
How long the effects last when smoking, vaporising and eating, what drug, set and setting are, and which desired and unwanted effects there are.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): hash and weed, the risks (in Dutch)
The risks in the short and the long term: a bad reaction, traffic, the heart, the lungs, addiction and missed chances.
drugsinfo.nl
- Trimbos Institute: information about cannabis (in Dutch)
Knowledge and figures from the Trimbos Institute about the plant, the substances and the effects.
trimbos.nl
Unit 4
Effects and risks
- Drugs Infolijn (Trimbos Institute): hash and weed, the effects (in Dutch)
How long the effects last when smoking, vaporising and eating, what drug, set and setting are, and which desired and unwanted effects there are.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): hash and weed, the risks (in Dutch)
The risks in the short and the long term: a bad reaction, traffic, the heart, the lungs, addiction and missed chances.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): what you need to know about cannabis (in Dutch)
Independent information about the effects, the risks and using cannabis safely.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): what you can do during a bad trip (in Dutch)
What you can do yourself and what you can do for someone else when things go wrong.
drugsinfo.nl
- Drugs en Uitgaan (Trimbos Institute): first aid when things go wrong (in Dutch)
What to do when someone feels very ill, anxious or restless after use.
drugsenuitgaan.nl
- Drugs Infolijn (Trimbos Institute): the consequences of using cannabis at a young age (in Dutch)
Why the brain is extra vulnerable until about the age of 24 and what starting young can mean.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): cannabis and pregnancy (in Dutch)
Why doctors advise not to use cannabis during pregnancy and while breastfeeding.
drugsinfo.nl
- Drugs Infolijn (Trimbos Institute): if you use cannabis every day, are you addicted? (in Dutch)
The difference between physical and psychological dependence.
drugsinfo.nl
- Drugs en Uitgaan (Trimbos Institute): reduce the risks of hash and weed (in Dutch)
Practical tips to make the risks smaller: take it slowly, no tobacco, wait with edible forms, do not drive, and who is advised against using.
drugsenuitgaan.nl
- Jellinek: cannabis (in Dutch)
Explanation from Jellinek (addiction care) about effects, risks and help.
jellinek.nl
- Drugs Infolijn: 0900-1995, anonymous (in Dutch)
Call, e-mail or chat with questions about drugs, for yourself or for someone else.
drugsinfo.nl
How we write the questions
- Every question has an explanation and a source from the government or an independent organisation.
- We write neutrally and in plain language. We never name varieties or products and say nothing about what a coffeeshop sells.
- We only mention numbers that appear in a source.
- If we are unsure about a fact, the question stays out until it has been checked.
Sources checked on 5 October 2026.