Aug. 21, 2000 CHAMPAIGN, Ill. - Reaction time can be crucial, and children with attention deficit hyperactivity disorder can be out of step. A new study says that non-medicated ADHD kids are three times slower making quick decisions involving different tasks than their non-ADHD counterparts.
Slower reaction times, however, vanished when ADHD children were on methylphenidate (Ritalin), the most commonly used drug prescribed for the disorder. The study -- funded by the National Institutes of Health -- was published in the June issue of the Journal of Abnormal Child Psychology.
"The results suggest that ADHD kids can be quite successful when they are treated, in this case with Ritalin or methylphenidate, to deal with these problems of flexibility," said Arthur F. Kramer, a professor of psychology at the University of Illinois Beckman Institute for Advanced Science and Technology. "Treatment in these cases was completely effective, wiping out the deficit."
Kramer and UI doctoral student Nicholas J. Cepeda teamed with Cepeda's father, Manuel L. Cepeda, a child psychiatrist at the University of South Alabama, to compare reaction times of ADHD and non-ADHD children, all of whom had an average age of almost 9 and standardized IQs of about 94. All of the children were from low- to moderate-income homes.
They were tested in two experiments in a task-switching paradigm that measures executive control abilities; participants had to process relevant information, discard distractions and switch rapidly among different skills to make accurate decisions. In this case, children had to respond on a computer to questions of "how many" and/or "what number" when shown changing screens of numbers.
In one experiment, the two answers at first were the same number. Response times by all the children for switching between the questions were about 200 milliseconds longer than response times when the same question was asked repeatedly. When the answers differed, untreated ADHD children took almost 700 milliseconds longer to respond correctly during a switch between the two questions than they had when they answered the same question repeatedly. Medicated children and the non-ADHD children still took 200 milliseconds.
In the second experiment, which involved only ADHD children and unpredictable switching patterns, the non-medicated children again took three times longer to switch between tasks.
"This can't be good," Kramer said. "When a teacher says, 'Hey, pay attention,' these kids will have to be switching from one thing to something else. When they are teen-agers and go out to drive a car, a hundred milliseconds can become quite important if you have to swerve or apply the brakes."
The study gave a new look at cognitive changes and differences involved in ADHD, Kramer said. The results indicate that medication improves the ability of ADHD kids "to inhibit inappropriate task skills and prepare for a new task regardless of whether the task switch is frequent and predictable or infrequent and unpredictable," the authors wrote.
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