Apparently even legal, profitable drugs may be bad for kids. Shocking. Reuters reports: In the United States between 3 percent and 5 percent of children are diagnosed with attention deficit disorder, marked by reduced ability to concentrate, difficulty in organizing and impulsive behavior. Patients are commonly prescribed stimulants but the practice is sometimes controversial. William Carlezon of McLean Hospital and Harvard MedicalSchool in Boston and colleagues raised two groups of rats. One was given Ritalin, known generically as methylphenidate, during the rat equivalent of pre-adolescence, while the other was given a salt water injection. When they matured, the rats were tested for "learned helplessness" -- how quickly they gave up on behavioral tasks under stress. "Rats exposed to Ritalin as juveniles showed large increases in learned-helplessness behavior during adulthood, suggesting a tendency toward depression," Carlezon said in a statement.