Attention-deficit/hyperactivity disorder is linked to delayed brain development
By Amy Ellis Nutt –
For the first time, scientists can point to substantial empirical evidence that people with attention-deficit/hyperactivity disorder have brain structures that differ from those of people without ADHD. The common disorder, they conclude, should be considered a problem of delayed brain maturation and not, as it is often portrayed, a problem of motivation or parenting.
In conducting the largest brain imaging study of its kind, an international team of researchers found that ADHD involves decreased volume in key brain regions, in particular the amygdala, which is responsible for regulating the emotions. Although the study, published Wednesday in the Lancet Psychiatry, included children, adolescents and adults, the scientists said the greatest differences in brain volume appeared in the brains of children.
Of seven subcortical brain regions targeted in the study, five, including the amygdala, were found to be smaller in those with ADHD, compared with those in a control group. The other regions that showed reductions in volume were: the caudate nucleus (which has been linked to goal-directed action), the putamen (involved in learning and responding to stimuli), the nucleus accumbens (which processes rewards and motivation) and the hippocampus (where memories are formed).
The first author, geneticist Martine Hoogman of Radboud University in the Netherlands, said the amygdala “is a structure that is not so well known to be implicated in ADHD. … We do know from other functional studies of the amygdala that it is involved in emotion regulation and recognizing emotional stimuli. But it is also involved in the process of [inhibiting] a response. Both cognitive processes are characteristic of ADHD, so it does make sense to have found this structure to be implicated in ADHD.”