Editorial: Cannabis rating needs careful thought

Research from Maastricht University, which monitored 2,437 young people aged 14 to 24 for four years, found that frequent cannabis use during adolescence and young adulthood increased the risk of psychotic symptoms developing later in life. And the New Scientist reported last month on "overwhelming" evidence that under-21s should not use marijuana because of the risk to the developing brain.

And it isn't just the long-term risks. Young people who misuse cannabis and other substances, including alcohol, are effectively sabotaging their own life chances. Of course, there are reasons why disadvantaged young people turn to cannabis and in many ways it's a vicious circle: drugs can blot out what's going wrong for them but also make it harder to put things right. Liam Black, director of Jamie Oliver's Fifteen, takes in regular batches of disadvantaged young people and turns out qualified chefs. In an interview earlier this year, he was voluble on the subject of cannabis, calling it a "scourge", leading to young people who cannot cope with the rigours of a kitchen.