Researchers from the international ENIGMA-ADHD working group have found that people with attention-deficit/hyperactivity disorder (ADHD) have subtle differences in the cerebral cortex, the brain’s outer layer. This is the second study conducted by the working group, which includes academics from Brighton and Sussex Medical School (BSMS), and was published in the American Journal of Psychiatry.
ADHD symptoms include inattention and/or hyperactivity and acting impulsively. The disorder affects more than one in 20 (5.3%) children worldwide, and two-thirds of those diagnosed continue to experience symptoms as adults.
In the largest study to date looking at the cortex of people with ADHD, researchers combined brain imaging data on almost 4,000 participants aged between four and 63 year, both with and without a diagnosis of ADHD, from 37 research groups worldwide. The differences in the brain were only significant for children and did not hold for adolescents or adults. As these differences were subtle and detected only at a group level, these brain images cannot be used to diagnose ADHD or guide its treatment.
These subtle differences in the brain’s cortex were not limited to children with the clinical diagnosis of ADHD; they were also present, albeit in a less marked form, in children who displayed ADHD symptoms. The researchers found more symptoms of inattention to be associated with a decrease in the brain’s cortical surface area. Furthermore, siblings of those with ADHD showed changes to their cortical surface area that resembled their affected sibling. This suggests that familial factors such as genetics or shared environment may play a role in brain cortical characteristics.
Commenting on the study, Professor Mara Cercignani, Academic Director of Clinical Imaging Sciences Centre at BSMS and contributing author on the study, said: “This study is an example of the importance of large, multi-centre studies for understanding conditions such as ADHD, characterised by very subtle brain changes. It simply would not be possible for a single site to recruit a sufficiently large sample. This type of study is becoming more common and it is important for BSMS researchers to be part of this effort.”
The ENIGMA-ADHD working group is one of more than 50 working groups of the ENIGMA Consortium, in which international researchers pull together to understand the brain alterations associated with different disorders and the role of genetic and environmental factors in those alterations.
Neil Harrison, formerly Professor (Honorary Consultant) of Neuropsychiatry at BSMS, and Dr Matt Gabel, MND Association Lady Edith Wolfson Junior Non-Clinical Fellow at BSMS, were also contributing authors on the study.
The working group will now look at additional key features in the brain, such as the structural connections between brain areas, as well as increasing the representation of adults affected by ADHD, in whom limited research has been performed to date.