Vol. 11, No. 1, 2005 Page 6
A study of rats indicates that Ritalin (methylphenidate) can permanently alter the brain in ways that could put its users at risk for adult depression, leading the study's authors to caution against the overuse of this drug.
William Carlezon and colleagues exposed rats to twice-daily doses of Ritalin during a period equivalent to human development from age 4 to age 12. The researchers tested the behavior of the rats when they reached adulthood and found that compared to a control group receiving saline rather than Ritalin, the Ritalin- treated animals tended to "give up" quickly on a test measuring their ability to deal with stress. The Ritalin-exposed rats also were less interested in cocaine than normal lab rats—an indication of alterations in brain systems involving dopamine, a neurotransmitter involved in causing a pleasurable response to rewards.
The researchers note that Ritalin has a positive effect on the behavior of many children with attention deficit hyperactivity disorder. They voice concerns, however, over the large number of children taking the drug and the high rate of misdiagnosis of ADHD in children exhibiting normal exuberance and immaturity, "especially when considering health effects that can last through adulthood."
The researchers caution that their animal study does not prove that the same effects occur in humans, but they say that it is critical for researchers to investigate this possibility.
"New study shows early Ritalin may cause long-term effects on the brain," news release, American College of Neuropsychopharmacology. This study was reported at the ACN conference in San Juan, Puerto Rico in Dec. 2004.
"Understanding the neurobiological consequences of early exposure to psychotropic drugs: linking behavior with molecules," Neuropharmacology, Vol. 47, Supplement 1, 2004, 47-60. Address: William Carlezon, Department of Psychiatry, Harvard Medical School and McLean Hospital, MRC 217, 115 Mill Street, Belmont, MA 02478, carlezon@mclean.harvard.edu.