Parents of children with attention deficit hyperactivity disorder (ADHD) are often concerned about the safety and long-term effects of medications used to help manage ADHD symptoms. But a recent animal study by a Wake Forest Baptist research team suggests that these fears may be unfounded. In this study of juvenile monkeys, the researchers found that Ritalin – the stimulant drug most commonly prescribed for ADHD – did not affect the developing brain, physical growth, or increase the risk of later substance abuse.
The research team, which was led by Linda Porrino, Ph.D. and Michael A. Nader, Ph.D., of the Department of Physiology and Pharmacology at Wake Forest Baptist, published their findings online in the July 2012 journal Neuropsychopharmacology. The researchers reported no conflicts of interest.
ADHD affects 5 to 7 percent of elementary school children in the United States. The condition is characterized by inattentiveness, impulsivity, and overactivity. Children (and adults) with ADHD may display one or more of these behavioral symptoms.
Psychostimulant drugs are commonly used to treat ADHD in concert with therapy and other non-drug support. It is thought that these drugs stimulate the production of certain substances in the brain, which helps pathways in the brain work more efficiently. Although medications do not cure ADHD, they can help to control symptoms so a child can focus, complete schoolwork, and function better in everyday life. It is not clear, however, whether medications can help children learn or improve their academic skills. Other research funded by the National Institute of Mental Health (NIMH) shows that medication is most effective when the doctor who prescribes the drug monitors treatment regularly and adjusts the dose based on the child's needs
Methylphenidate (MPH), sold under the brand name Ritalin, is the psychostimulant drug most commonly prescribed for ADHD. More than 11 million prescriptions for Ritalin are written every year in the United States, more than in any other country in the world. Yet little is known about the long-term effects of these drugs.
Need to Know: The ADHD Treatment Plan
Psychostimulant medications are only part of an ADHD treatment plan. Effective treatments for ADHD include a comprehensive approach to both the child and the family. Combining medications with behavioral therapy, counseling, and practical support can help children with ADHD and their families to better cope with day-to-day challenges.
What the Researchers Did
For the study, Nader and Porrino’s team selected 16 juvenile monkeys, which were equivalent in age to 6 to 10 year-old humans. Researchers divided the animals into two groups of eight. One group served as the control and received no medication. The other eight animals were treated with a therapeutic dose of MPH (Ritalin). Treatment lasted for one year, the equivalent of about four years in children.
Brain chemistry and structure were measured by imaging the monkeys’ brains both before and after the study. Researchers also tracked developmental milestones, which allowed them to detect any impact of Ritalin on physical growth.
After the MPH treatment and imaging studies were completed, Nader and Porrino’s team allowed the animals to self-administer cocaine over the next several months. To measure how vulnerable the monkeys were to substance abuse after the treatment, the researchers tracked how likely the animals were to use the cocaine, how quickly they used it, and how much they used.
What the Researchers Found
The research team found no differences between the two groups on any of the three measures. Imaging tests showed no difference in structural changes in the brain of monkeys treated with Ritalin during adolescence. Developmental milestones were reached at the same time in each group. And monkeys treated with Ritalin were not more likely to use the cocaine than the control animals.
“After one year of drug therapy, we found no long-lasting effects on the neurochemistry of the brain, no changes in the structure of the developing brain. There was also no increase in the susceptibility for drug abuse later in adolescence,” Porrino said. “We were very careful to give the drugs in the same doses that would be given to children. That’s one of the great advantages of our study is that it’s directly translatable to children.”
Study Strengths and Limitations
Although this research was performed on monkeys, not children, and sample size was relatively small, it is still a strong study. Investigators explained that the non-human primates used in the study – i.e. monkeys – are excellent models for developmental research because their relatively long childhood and adolescence are marked by hormonal and physiological changes that mirror humans’.
In addition, researchers noted, their findings were strengthened by a “sister” study conducted simultaneously at Johns Hopkins University, which used slightly older animals and different drugs. The Johns Hopkins researchers reported similar results.
“We feel very confident of the results because we have replicated each other’s studies within the same time frame and gotten similar results,” Porrino said. “We think that’s pretty powerful and reassuring.”
Why It’s Important
Up until now, little has been known about the long-term effects of stimulant drugs commonly used to treat ADHD. This study suggests that Ritalin, when used as part of an ADHD treatment plan, does not alter brain structure, physical development, or increasing the risk of later substance abuse.
For parents wondering what the best treatment course for children with ADHD, this study should lessen fears about the long-term effects of Ritalin. It is not clear whether these results could be extrapolated to other psychostimulant medications, although researchers included other drugs in their commentaries.
“Our study showed that long-term therapeutic use of drugs to treat ADHD does not cause long-term negative effects on the developing brain, and importantly, it doesn’t put children at risk for substance abuse later in adolescence,” Porrino said.