|Preschoolers with ADHD Improve with Low Doses
The first long-term, large-scale study designed to determine the
safety and effectiveness of treating preschoolers who have attention
deficit/hyperactivity disorder (ADHD) with methylphenidate (Ritalin)
has found that overall, low doses of this medication are effective
and safe. However, the study found that children this age are more
sensitive than older children to the medication’s side effects
and therefore should be closely monitored. The 70-week, six-site
study was funded by the National Institutes of Health’s National
Institute of Mental Health (NIMH) and was described in several
articles in the November 2006 issue of the Journal of the American
Academy of Child and Adolescent Psychiatry.
“The Preschool ADHD Treatment Study, or PATS, provides us with
the best information to date about treating very young children
diagnosed with ADHD,” said NIMH Director Thomas R. Insel, MD. “The
results show that preschoolers may benefit from low doses of medication
when it is closely monitored, but the positive effects are less
evident and side-effects are somewhat greater than previous reports
in older children.”
Methylphenidate is the most commonly prescribed medication to
treat children diagnosed with ADHD. But its use for children younger
than 6 years has not been approved by the Food and Drug Administration.
And until PATS, very few studies — and no large-scale ones — have
been conducted to collect reliable, consistent data to help guide
practitioners treating preschoolers with ADHD.
The 303 preschoolers enrolled in the study ranged in age from
3 to 5 years. The children and their parents participated in a
pre-trial, 10-week behavioral therapy and training course. Only
those children with the most extreme ADHD symptoms who did not
improve after the behavioral therapy course and whose parents agreed
to have them treated with medication were included in the medication
study. In the first part of the medication study, the children
took a range of doses from a very low amount of 3.75 mg daily of
methylphenidate, administered in three equal doses, up to 22.5
mg/day. By comparison, doses for school-aged children usually range
from 15 to 50 mg total daily.
The study then compared the effectiveness of methylphenidate to
placebo. It found that the children taking methylphenidate had
a more marked reduction of their ADHD symptoms compared to children
taking a placebo, and that different children responded best to
“The best dose to reduce ADHD symptoms varied substantially among
the children, but the average across the whole group was as low
as 14 mg per day,” said lead author Laurence Greenhill, M.D., of
Columbia University/New York State Psychiatric Institute. “Preschoolers
with ADHD may need only a low dose of methylphenidate initially,
but they may need to take a higher dose later on to maintain the
To ensure the safety of the very young children involved, the
study was governed by a strict set of ethical standards and additional
review boards. The children’s health was monitored carefully and
repeatedly throughout the study’s duration. Their parents were
repeatedly consulted for consent prior to every step of the program.
The researchers also reviewed the teacher ratings of the children
who attended preschool at various stages in the study.
Similar to 1999 results found in NIMH’s Multimodal Treatment Study
of Children with ADHD (MTA study: http://www.nimh.nih.gov/childhp/mtaqa.cfm),
and other studies on school-aged children, the medication did appear
to slow the preschoolers’ growth rates. Throughout the duration
of the study, the children grew about half an inch less in height
and weighed about 3 pounds less than expected, based on average
growth rates established prior to the study.
Currently, no data exist that track long-term growth rate changes
among preschoolers with ADHD who are medicated with methylphenidate.
However, a five-year-long follow-up study is underway to track
the children's physical, cognitive, and behavioral development,
as well as health care services the family is using to care for
the child. Those data will be available in two to three years.
Finally, 89 percent of the children tolerated the drug well, but
11 percent — about 1 in 10 children — had to drop out
of the study as a result of intolerable side effects. For example,
while some children lost weight, weight loss of 10 percent or more
of the child’s baseline weight was considered a severe enough side
effect for the investigators to discontinue the medication. Other
side effects included insomnia, loss of appetite, mood disturbances
such as feeling nervous or worried, and skin-picking behaviors.
Despite concerns that stimulants may increase blood pressure or
pulse, any changes seen in the children’s blood pressure or pulse
“The study shows that preschoolers with severe ADHD symptoms can
benefit from the medication, but doctors should weigh that benefit
against the potential for these very young children to be more
sensitive than older children to the medication’s side effects,
and monitor use closely,” concluded Dr. Greenhill.
PATS was conducted by researchers at Columbia/New York State Psychiatric
Institute, Duke University, Johns Hopkins University, New York
University, the University of California Los Angeles, and the University
of California Irvine, in collaboration with NIMH staff under a
The National Institute of Mental Health (NIMH) mission is
to reduce the burden of mental and behavioral disorders through
research on mind, brain, and behavior. More information is available
at the NIMH website, http://www.nimh.nih.gov.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — includes 27 Institutes and
Centers and is a component of the U.S. Department of Health and
Human Services. It is the primary federal agency for conducting
and supporting basic, clinical and translational medical research,
and it investigates the causes, treatments, and cures for both
common and rare diseases. For more information about NIH and
its programs, visit www.nih.gov.