A study, led by McLean Hospital’s William Carlezon and Susan Andersen, found that adult rats given Ritalin as juveniles behaved differently than their placebo-treated counterparts in a host of tests that reflect mood and attention. Published in the Dec. 15, 2003 issue of Biological Psychiatry, the study follows up previous work by the researchers showing that young rats given Ritalin were less likely to find cocaine pleasurable as adults. For the new study, Carlezon and Andersen raised two sets of rats: one was given Ritalin during the rat equivalent of pre-adolescence, while the other was given saline. At adulthood, all of the rats were examined in a model of “learned helplessness,” which tested 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,” said Carlezon, director of McLean Hospital’s Behavioral Genetics Laboratory. Carlezon and Andersen do not believe the effects they see in their rats are specific to Ritalin. Rather, they believe they are observing a general effect of how stimulant drugs affect the way that neuronal connections become cemented into place during development.