In 1997 alone, nearly five million people in the United States were prescribed Ritalin -- most of them young children diagnosed with attention deficit disorder (ADD). Use of this drug, which is a stimulant related to amphetamine, has increased by 700 percent since 1990. And this phenomenon appears to be uniquely North American: 90 percent of the world's Ritalin is used in the United States. Is this a cause for alarm -- or simply the case of an effective...