Individuals diagnosed with attention deficit hyperactivity disorder (ADHD) have been found to have smaller brain volume compared to those without the condition. A new study placed emphasis on the differences in brain volume with which brain scans were used to compare people with ADHD to those without the disorder.
Published in the Lancet Psychiatry on Wednesday, the study examined data gathered from other studies on ADHD found at 23 research sites globally. Participants were aged between 4 and 63 years old; these included 1,713 individuals diagnosed with ADHD and the other 1,529 without the condition.
Known as a neuro-developmental disorder, the symptoms of ADHD can include hyperactivity, inattentiveness and impulsivity. According to CNN, over one in 20 people below the age of 18 is diagnosed with the disorder. More than half of these diagnosed people carry the symptoms into their adult life.
The study’s results showed that the overall brain volume along with the volumes of five regions in the brain were smaller among individuals with ADHD compared to others. Specifically, the biggest difference took place in the part of the brain that controls emotions- the amygdala.
Dr. Martine Hoogman, the study’s lead author, stated that there is a need to further look into the relationship between age and the symptoms of ADHD. “Children with ADHD can outgrow the disorder ... the adults in our study do have a current diagnosis of ADHD, so this cannot explain this effect," said Hoogman, who is also a post-doctoral researcher at the Netherlands’ Radboud University Medical Center, adding: "It seems that there is a shift in the maturation of the brain but later in life it is caught up.”
Aside from ADHD, previous studies have also shown brain volume differences in relation to other psychiatric disorders; these include bipolar disorder, obsessive compulsive disorder (OCD), depression and schizophrenia. The symptoms of ADHD among children are often related to emotions, such as poor tolerance for frustration and emotional reactivity.
Dr. Jonathan Posner, an assistant professor at Columbia University’s psychiatry department, said symptoms of ADHD relating to emotions have often been deemed as less important components. "These findings would suggest that it's possible that there's actually a more primary disturbance in emotional processing," Posner explained.
He also noted that symptoms of ADHD could also be associated with motivation, cognitive control and even the processing of rewards, which may result to substance abuse. Therefore, it is a possibility that children with ADHD could face greater risks for developing problems relating to substance abuse. "It's possible because that underlying vulnerability is seen in both disorders -- or that underlying abnormality,” he added.
