Three new studies, conducted on animals, suggest that misuse of Ritalin in human children may have long-term brain and behavioral effects. Ritalin is a powerful stimulant used with growing frequency to treat Attention Deficit Hyperactivity Disorder (ADHD) in children and adults.
The first study, by a team of Harvard Medical School researchers led by William A. Carlezon, Jr., suggests that pre-adolescent exposure to methylphenidrate (Ritalin) in rats may cause various behavioral changes that endure into adulthood. These include increased signs of depression and reduced comfort with familiar environments.
Dr. Cindy Brandon and her Fitch University of Health Sciences colleagues at the Chicago Medical School examined how low doses of Ritalin affect cells of the brain chemical dopamine, also in adolescent rats. The studies produced differing results on the question of whether Ritalin use increased or decreased sensitivity to the rewarding effects of cocaine. Dr. Branson cited other recent research associating early exposure to Ritalin in humans with increased lifetime use of nicotine and cocaine.
Adult rats treated with Ritalin prior to adolescence were less responsive to natural rewards, including sugar and sex, according to findings by Dr. Carlos Bolanos and colleagues at the University of Texas’ Southwestern Medical Center. These rats were also found to be more sensitive to stressful situations, and showed increased anxiety-like behaviors.
The studies appear in the current issue of the journal Biological Psychiatry, and were conducted with grants from the National Institutes of Mental Health’s (NIMH) National Institute on Drug Abuse. In commentary to the accompanying papers, the directors of both institutes caution against directly extrapolating findings in rodents to humans. They note that while substantial research supports the safety and effectiveness of Ritalin when prescribed and taken properly, “there are still questions about adverse neural or behavioral consequences of long-term psycho-stimulant treatment in children.”
In an essay published alongside the studies, Harvard University Provost (and former NIMH Director) Steven Hyman discussed the difficulties in comparing these studies on rats to humans. He noted the importance of understanding that children who suffer from certain categories of ADHD are themselves at elevated risk for substance abuse. But Hyman also went on to describe ‘major worries’ that prescribing behavior-altering drugs like Ritalin to human children may introduce “irreversible, malign changes in the circuits of developing brains.”
Hyman observed that prescription rates for Ritalin are increasing, and that many children who are prescribed Ritalin for ADHD do not meet diagnostic criteria for the condition. He discussed recent evidence of increases in Ritalin prescriptions among preschool-age children.
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