-- 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
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
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
"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."
Swanson and colleagues note that the study did not test the
sustained-release stimulant medications that are now the standard treatment for
Omar Khwaja, MD, PhD, a neurologist at Children's Hospital inB Boston,
last year analyzed studies of different ADHD drugs and found strong evidence
drugs do, indeed, stunt children's growth . In fact, Khwaja and colleagues
calculated a growth effect that almost exactly matches the effect seen in the
But Khwaja agrees with Swanson that nobody yet knows what the long-term
results of this side effect will be.
"Whether there will be rebound growth at end of puberty, the jury is
still out," Khwaja tells WebMD.
"Parents have to be aware that stimulants are an enormous benefit to a
lot of children with ADHD, but there is reason to be cautious with all
medicines that affect the brain," he says.B "Growth monitoring
should be standard practice for kids taking these medications."
Swanson and colleagues report their findings in the August issue of the
Journal of the American Academy of Child and Adolescent Psychiatry.
Other findings from this largeB study show that both
ADHD drugs and behavioral therapy work in children.
By Daniel DeNoon
Reviewed by Louise Chang
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