WILLIAM WAS LIVING the good life. He had a beautiful family, a big house in the suburbs, everything he had ever wanted. Then he started sniffing cocaine and almost lost it all. "It's a lie that cocaine's not addictive," he says. "I didn't choose to be an addict. Quitting cocaine was the only thing I couldn't do by myself. I'll be a recovering addict day by day for the rest of my life."

Drugs: powerful substances

William experienced firsthand the awesome power of drugs. A drug is a chemical that acts on the brain and nervous system. It can cause changes in feelings, behavior, and the way the body works. A drug can be as old as opium—discovered between 4000 and 2000 B.C. —or as new as a designer drug manufactured last week in an illegal laboratory. For...