The linked newspaper article from the Guardian concentrates on the UK, and the headline indicates that the UK is the worst country in Europe for under age drug-taking [ie among 13 year olds]. There is a graphic comparing EU countries across the board. The important statistics are that cocaine use is rising across Europe and that cannabis use in the Uk among 15-30 year olds has actually gone down, with Spain now the largest users, followed by the Czech Republic and Italy. The newspaper report is a bit garbled and the full report needs to be browsed. Comments would be useful.
If usage in the UK has fallen is there any connection to making cannabis a category C drug? That has to be the interesting question for researchers. Equally, if it has fallen, is it then likely to rise again if it is reclassified? Watch this space.