There are several controversies surrounding the use of Ritalin, or methylphenidate, a stimulant prescribed for children who have an abnormally high level of activity or attention deficit hyperactivity disorder (ADHD). While Ritalin appears to calm hyperactive children, some worry that it may lead to the abuse of other drugs later in life. However, in a study with rats, Harvard researchers Susan Andersen, William Carlezon, and their colleagues found adult rats that were given Ritalin as juveniles spent less time seeking out cocaine than did their Ritalin-free peers. Another concern about Ritalin is that it may cause permanent changes in the brain. Andersen and her colleagues found that the Ritalin-exposed animals did display lasting neurological changes. Most notably, they had elevated levels of a protein called CREB, which plays a role in a wide variety of brain functions. Is Ritalin working its cocaine-aversive effects by upping CREB production? The researchers think this may be the case, at least in part. While cocaine-avoidance might be beneficial, high levels of CREB could also have harmful consequences. The changes in CREB occur in a part of the brain that is involved in a variety of other basic activities, such as eating and sex.