LONDON — Children with attention-deficit hyperactivity disorder have several brain regions that are slightly smaller than usual, more evidence that the disorder should be considered a neurological condition, a new study says.
The study, the largest review of ADHD patients’ brain scans ever conducted, might also provide clues for new treatments.
‘‘If you know what region of the brain is involved in ADHD, you could possibly target that part with medication,’’ said Martine Hoogman of Radboud University in the Netherlands, the study’s lead author.
ADHD causes inattention, hyperactivity, and impulsivity, although a given person may not show all those traits.
Hoogman and her colleagues analyzed MRI scans for 3,200 people aged four to 63, of whom 1,713 had ADHD. They found that the brains of children with the condition were slightly smaller in five regions, including those that control emotions, voluntary movement, and understanding.
The scientists reviewed one scan per person and found no effect from ADHD medications.
Hoogman said the findings support previous theories that the brains of people with ADHD may develop more slowly, but that those differences are mostly wiped out by the time children grow up.
‘‘By the time they become adults, the differences in their brains are not significant anymore,’’ she said. The study was paid for by the National Institutes of Health and was published online Wednesday in the journal Lancet Psychiatry.
Some experts called the findings interesting but said there wasn’t enough information to link the brain differences to behavioral problems seen in people with ADHD. ‘‘The study confirms there are structural differences in the brains of people with ADHD, but it doesn’t tell us what they mean,’’ said Graham Murray, a Cambridge University psychiatrist who was not part of the research.
‘‘Having less brain in several regions sounds bad, but it’s not as simple as that,’’ he said, pointing out that decreased brain matter can sometimes be beneficial — like in teenagers, when the outer cortex of their developing brains becomes thinner as their intellectual capacity grows.
‘‘The brain is very good at adapting,’’ Murray said. ‘‘Just because you have less brain volume doesn’t condemn the child to not being able to function well.’’
