The condition is linked with inattention, hyperactivity and strong impulses and is thought to affect one in 20 under-18s. They found that 1,713 children who had ADHD had slightly smaller brain regions, particularly the amygdala, part of the brain that control emotions, voluntary movement and understanding.
In conducting the largest brain imaging study of its kind, an worldwide team of researchers found that ADHD involves decreased volume in key brain regions, in particular the amygdala, which is responsible for regulating the emotions.
Researchers who pinpointed brain differences in people with attention-deficit/hyperactivity disorder (ADHD) say their findings show the condition should be considered a brain disorder.
"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", Hoogman said in a journal news release.
The researchers studied MRIs of the brain to identify the regions possibly affected by ADHD, but Posner says it's not practical to use MRIs to diagnose the disorder-at least not yet.
The differences observed in their study were most prominent in children, but also present in adults with the condition.
Hoogman said: "We hope that this will help to reduce stigma that ADHD is "just a label" for hard children, or caused by poor parenting".
Among the regions found to be underdeveloped in the case of ADHD patients was the hippocampus, which may contribute to the disorder through its role regulating emotion and motivation, the Lancet study said.
"These differences are very small - in the range of a few percent - so the unprecedented size of our study was crucial to help identify these", Hoogman said.
For the new study, Dr. Hoogman and colleagues measured differences in brain structure from MRI scans of 1,713 participants diagnosed with ADHD, and in 1,529 other people (the controls) who did not have ADHD. It is the work of the ENIGMA Consortium, an global multidisciplinary group that is investigating genetic and brain-imaging differences in psychiatric disorders.
Attention Deficit Hyperactive Disorder (ADHD) results, in essence, in sudden bursts of hyperactivity, coupled with inattention and a frequent inability to focus.
Notably, no differences were found in the brain size of people who took ADHD drugs and those who did not. He also calls for further studies to track brain differences in the development of ADHD, and suggests that there should also be an investigation of any medication effects. "So because this study was orders of magnitude higher in terms of participants, and because it involved sampling broadly and internationally, it gives us more confidence".