The debate on cannabis legalisation is gaining momentum worldwide. In many countries, laws are being amended or discussed. But what do scientific studies actually say about the consequences of legalisation?

This page offers an accessible, fact-based overview of the current state of research — and shows why newer scientific methods are needed to get clear answers.

What does the science say — and where are the problems?

Opinions on whether cannabis legalisation has positive or negative consequences differ. Many studies have examined the effects of legalisation. Some see advantages such as a reduction in crime and additional tax revenue, while others point to possible health risks or an increase in use.

However, the studies so far deliver contradictory results. The reason: they mostly measure only correlational relationships and therefore cannot conclusively show whether cannabis legalisation is in fact the cause of the observed patterns.