Call it pot, grass, weed, or any one of nearly 200 other names, marijuana is, by far, the world’s most commonly used illicit drug—and far more dangerous than most users realize. So, there is just cause for alarm when adolescent marijuana use increases, as it did in the mid-1990’s, and the age at which youngsters first experiment with pot starts to drops. Its source, the hemp plant (cannabis sativa), was being cultivated for psychoactive properties more than 2,000 years ago. Although cannabis contains at least 400 different chemicals, its main mind-altering ingredient is THC (delta-9-tetrahydrocannabinol).The amount of THC in marijuana determines the drug’s strength, and THC levels are affected by a great many factors, including plant type, weather, soil, and time of harvest. Sophisticated cannabis cultivation of today produces high levels of THC and marijuana that is far more potent than pot of the past. THC content of marijuana, which averaged less than 1 percent in 1974, rose to an average 4 percent by 1994. For the highly popular form of marijuana called Sinsemilla (from the Spanish "without seeds"), made from just the buds and flowering tops of female plants, THC content averages 7.5 percent and ranges as high as 24 percent. As for hashish, a resin made from flowers of the female plant, THC levels may be five to ten times higher than crude marijuana’s.
