United Press International
Saturday, October 12, 2002
BETHESDA, Md., Oct 08, 2002 (United Press International via COMTEX)
The reduced brain components could play a role in causing the over-activity, distractibility and impulsiveness that are hallmarks of ADHD, Judith Rapoport, chief of the child psychiatry branch at the National Institute of Mental Health and an author of the study, told United Press International. The findings of smaller brains "provide support in conjunction with other data like genetics that there is a clear biological factor in ADHD," Rapoport said.
She noted the smaller brains also were found in ADHD patients who never had taken Ritalin or other drugs used to treat the condition, so the size decrease is not caused by medications.
In the 10-year study, which appears in the Oct. 9 issue of the Journal of the American Medical Association, Rapoport and colleagues used magnetic resonance imaging or MRI to scan the brains of nearly 300 boys and girls ranging from ages 5 to 18. They found ADHD patients had brains 3-to-4 percent smaller, on average, than children without the condition. The ADHD kids also had smaller brain regions, including frontal lobes, temporal gray matter, basal ganglia and cerebella.
The study "helps to focus our attention on what brain regions may be doing things we didn't know very much about," F. Xavier Castellanos, a professor of child psychiatry and radiology at New York University School of Medicine in New York City and lead author of the study, told UPI. "For example, the cerebellum is a part of the brain we don't really understand and it seems to play a role in ADHD."
The smaller basal ganglia and cerebella, in particular, could account for some ADHD symptoms, Rapoport said. The basal ganglia is a part of the brain involved in planning and the reduced size could be related to the impulsiveness and restlessness seen in ADHD patients, she said. The cerebellum plays a role in coordinating movement so a decrease in this region may be linked to hyperactivity and increased movement, she said.
Brad Peterson, a psychiatrist at Columbia University in New York City, told UPI the research indicates the brain "starts out smaller and stays smaller" in children with ADHD. He said the finding that multiple regions of the brain were smaller in the ADHD kids "may suggest that there is no one area or structure" that causes the condition. Instead, a size decrease in many different brain regions may be necessary to cause the symptoms of ADHD, he said.
The smaller brain volumes might be the secondary results of other anatomical abnormalities, so the brain could possibly be suffering indirect effects from defects elsewhere in the body, Jerry Rushton, a pediatrician at the University of Michigan in Ann Arbor, Mich., told UPI.
The research also found the size reduction appears to have happened early on during brain development, Rapoport said, which could indicate that a critical signal or molecule is lacking during development.
Rapoport noted there are normal variations in brain size so this technique could not be used to diagnose people with ADHD. Also, the brains of the kids in the study do not appear to be progressing or getting smaller as they age, she said.
Copyright 2002 by United Press International.