ADHD Drugs May Slow Growth

While beneficial, stimulant medications may affect height -- at least temporarily

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HealthDay Reporter

MONDAY, April 5, 2004 (HealthDayNews) -- Stimulant medications used to calm children with attention deficit hyperactivity disorder may have an unexpected side effect -- slightly slower growth.

In a study appearing in the April issue of Pediatrics, researchers report that after two years of follow-up, stimulant medications used to treat ADHD are still effective, but they may slow growth in height a bit.

"Stimulant medications are really extremely safe medications with very few side effects," said one of the study's authors, James Swanson, a psychologist and professor of pediatrics at the University of California, Irvine. "I don't think this is necessarily a cause for great alarm in parents. The effect was rather modest, only about a centimeter less over a year."

Swanson also noted that many questions remain unanswered. For example, researchers don't know if children on ADHD medications will have a growth rebound later. He added that many children with ADHD are larger than average for their age, so the slight growth reduction for those on medication may just put them back into the normal height range.

It's estimated that 2 million children in the United States have ADHD, according to the National Institute of Mental Health. That translates to almost one child with ADHD in every classroom. Symptoms include an inability to focus, hyperactivity and impulsivity.

For the current study, Swanson and his colleagues followed up with 540 children with ADHD who had participated in an earlier randomized clinical trial. The trial compared the use of the stimulant medication Ritalin to behavioral therapy, a combination of Ritalin and behavioral therapy, or no treatment.

Children in the study were recruited from six sites across the United States and one in Canada. All were between 7 and 9 years old at the start of the study.

The first study lasted 14 months, and researchers found that the children who received medication or medication in conjunction with behavioral therapy had fewer symptoms than those who received no medication. Children on medication also grew slightly less than their non-medicated peers. Children on medication alone gained 4.85 centimeters, while those on combination therapy grew 4.25 centimeters. Kids receiving behavioral therapy grew an average of 6.19 centimeters, while a "control" group of children grew 5.68 centimeters.

After 24 months, the researchers followed up with the study participants and found that symptom reduction difference in the medication and non-medication groups had dropped by 50 percent.

Swanson said the researchers suspected this change was due to children in the medication group no longer taking their medication, or because those in the non-medication group may have started taking medication. That's because the researchers only supervised treatment for the first 14 months. After that, treatment decisions were made by the parents and the children's physicians.

For the new study, the researchers re-interviewed the children and parents to assess what was truly happening in treatment. With the new information, Swanson said they found that both the effects of medication and the effects of behavioral therapy were actually fairly consistent throughout the 24 months. They also confirmed that children on medication showed a slight reduction in height, but Swanson said the effect was less pronounced at 24 months. He said those assigned to medication grew about a centimeter less per year than those not on medication.

Dr. Ernest Krug, medical director of Beaumont Hospital's Center for Human Development in Royal Oak, Mich., said, "The issue of growth suppression is something we always monitor in kids on medication. This study reinforces the importance of careful follow-up of children when they're on medication. It's a good idea for them to be seen every three to four months."

With any medication, parents should be convinced that the drug is providing beneficial effects for their children without causing unreasonable side effects, Krug said.

More information

To learn more about ADHD, visit Children and Adults with Attention Deficit/Hyperactivity Disorder (CHADD) or the National Institute of Mental Health.

SOURCES: James Swanson, Ph.D., psychologist and professor of pediatrics, University of California Irvine; Ernest Krug, M.D., medical director, Center for Human Development, William Beaumont Hospital, Royal Oak, Mich.; April 2004 Pediatrics

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