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ADHD Drug Does Stunt Growth

After 3 Years on Ritalin, Kids Are Shorter, Lighter Than Peers
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WebMD Health News
Reviewed by Louise Chang, MD

July 20, 2007 - After three years on the ADHD drug Ritalin, kids are about an inch shorter and 4.4 pounds lighter than their peers, a major U.S. study shows.

The symptoms of childhood ADHD -- attention deficit hyperactivity disorder -- usually get dramatically better soon after kids start taking stimulant drugs. But this benefit may come with a cost, says James Swanson, PhD, director of the Child Development Center at the University of California, Irvine.

"Yes, there is a growth suppression effect with stimulant ADHD medications," Swanson tells WebMD. "It is going to occur at the age of treatment, and over three years it will accumulate."

Whether these kids eventually grow to normal size remains a question. Kids entered the study in 1999 at ages 7 to 9. The current report is a snapshot taken three years later. The 10-year results -- when the kids are at their adult height -- won't be in for two more years.

"The big question now is whether there is any effect on these kids' ultimate height," Swanson says. "We don't know if by the time they are 18 they will regain the height."

The finding appears to end decades of debate over whether stimulant medications affect children's growth. Less than 10 years ago, a National Institutes of Health panel concluded that the drugs carried no long-term growth risk.

That opinion was so widely accepted that the study authors -- who include most of the leading ADHD researchers in the U.S. -- did not warn parents that the study medication might carry this risk.

At the time, researchers thought that any short-term stunting of growth would be made up by a hypothesized "growth spurt" that would occur with continued treatment. But Swanson and colleagues saw no evidence of such a growth spurt.

Another widely accepted theory was that ADHD itself stunted kids' growth. But in a surprise finding, the study found that ADHD kids who do not take stimulant drugs are much larger than kids without ADHD. And these untreated kids continued to grow much faster than kids taking stimulant drugs.

Swanson says that children who had been taking ADHD drugs before the study began were smaller than kids who had not yet started treatment. Those who first began treatment at the start of the study were normal in size, but grew more slowly than normal kids as the study went on.

After three years, the growth suppression seemed to reach its maximum effect. That's also when the effect of the ADHD drug used in the study -- immediate-release Ritalin three times a day, every day of the year -- seemed to wear off.

"We compared the effect of medication relative to just pure behavioral treatment," Swanson says. "That effect was substantial at 14 months and reduced a bit at 24 months. But at 36 months the relative advantage of ADHD drugs over behavioral treatment is gone."

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