Cannabis has changed. Now more potent and addictive than ever, it bears little resemblance to what some were smoking twenty years ago. Yet teenagers are using it more and more, despite proven toxic effects on the brain. Loss of attention, and in some cases even IQ, school dropout, emotional isolation, and sometimes psychotic behavior — smoking weed has become a public health issue. Among young people, however, cannabis still has a positive image. It’s seen as less harmful than alcohol or cigarettes. French adolescents are the top consumers of cannabis in Europe.