According to a pharmacology professor, "joints that circulate today don't even chemically resemble those from the 70s. They're approximately eight times more concentrated. Their level of active substances is highly reinforced by the genetic selection of plants. These new varieties of pot, of which Canada is a production leader, have a strong concentration of hallucinogenic components. Therefore, a teenager can now have a bad trip after smoking a simple joint."

Overdoses that require psychiatric hospitalization are rare: of the tens of thousands of people who participated in raves last year, only a few needed to be attended to by the on-site medical staff. What else is being done? Twice a month, in raves or free parties (raves for the initiated that aren't sponsored and are usually free), volunteer organization and/or medical teams test the composition of the available ecstasy tablets.

Drops of formol and sulfuric acid deposited in the pill or the powder makes a colour appear. If black appears, it indicates MDMA (the constitutive molecule in ecstasy), which is the colour of more than half of the tablets tested. Orange means it's an amphetamine. Green, a hallucinogen. In 30% of cases, the colour doesn't change. "Which means that we can't identify the substance," explains Sarah, a doctor who conducts the tests. "Fortunately, people often leave them for us so that we can have them analyzed in a lab."

But at a typical testing rave, only 50 to 200 tablets are randomly tested a tiny number compared to the 6,000 young people sweating to the rhythm of the trance. "Generally, the products come in batches or lots and the impact of the test is quickly felt," says the coordinator of a medical aid mission in a rave.