In the latest in ADHD news, a new study, published this month in The Lancet, adds to the growing body of evidence that ADHD in children is the result of delayed brain maturation.

Researchers from an ADHD Working Group within an international consortium of scientists associated with the University of Southern California’s ENIGMA Network, conducted the largest study of brain imaging of people with and without ADHD, across nine countries with participants’ ages spanning six decades. They found structural differences in five areas of the brain — and the greatest disparities in volume were seen in children.

The findings of this ADHD research reinforced previous research had already pointed to less development of the caudate (involved in motor control, procedural and associative learning, and inhibition of actions) and putamen (also involved in movement and learning) regions.

But the study revealed for the first time disparities in the maturity of the accumbens (important for functions like motivation and reward), the amygdala (which deals with memory, decision-making, and emotional reactions) and the hippocampus (which, among other things, converts short-term memory to long term).

The results, say researchers, thoroughly dispel the stigma of naughtiness attached to too many children with ADHD.

“The results from our study confirm that people with ADHD have differences in their brain structure and therefore suggest that ADHD is a disorder of the brain,” said Martine Hoogman of Radboud University in the Netherlands and the study’s lead author, in a news release. “We hope that this will help to reduce stigma that ADHD is ‘just a label’ for difficult children or caused by poor parenting.”

What this means in terms of diagnosis and treatment of ADHD in children is unclear; the study’s conclusion stopped short of offering suggestions. But the findings regarding the disparity in the size of the amygdala, the brain’s emotional center, is particularly notable, as emotional problems often accompany ADHD but are not currently classified as symptoms. If that changes, it may make it easier for doctors to diagnose accurately, but could muddy the waters for laypeople on the front lines of diagnosis — parents and teachers.

The study’s findings supports the prevailing theory among experts that the smaller brains of children with ADHD may, as they grow into adulthood, match in volume the brains of children without ADHD. So while there may not be any long-term structural differences between children with ADHD and without, as The Swaddle reported last year, if ADHD in children is not treated early enough, a child may always face an educational lag — even if his brain does catch up.