According to a new study conducted by Dr. Martine Hoogman, as many as five regions of the brain may not be fully developed in children who are diagnosed with attention-deficit hyperactivity disorder (ADHD).

According to the study, “Subcortical brain volume differences in participants with attention deficit hyperactivity disorder in children and adults: a cross-sectional mega-analysis” (Hoogman M, et al. Lancet Psychiatry. Feb. 15, 2017,, about 5.3 percent of children are diagnosed with ADHD worldwide, with symptoms continuing noticeably for about two-thirds of those into adulthood.

“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,” Dr. Hoogman, Ph.D., said in a news release posted Feb. 20, 2017 by the American Academy of Pediatrics.

“We hope that this will help to reduce stigma that ADHD is ‘just a label’ for difficult children or caused by poor parenting.”

The researchers from the international ENIGMA ADHD working group were funded by the US National Institutes of Health. They conducted what they believe has been the largest study of brain differences among those with and without ADHD, analyzing MRI data from 1,731 subjects with ADHD, and 1,529 controls, ranging in age from 4 to 63 years.

Results: The researchers found that those with ADHD had smaller brain volumes in the accumbens, amygdala, hippocampus, caudate, and putamen regions, with bilateral impact on the caudate and putamen. In addition, the intracranial volume was lower.

The findings on the accumbens, amygdala and hippocampus are new. However, Dr. Hoogman stressed that similar differences in brain volume are also seen in other psychiatric disorders, “especially major depressive disorder.”

The impact seen on the amygdala, which regulates emotion, is significant and can explain much for teachers, therapists and family members struggling to understand the emotional dysregulation so often exhibited by such children.

The team characterized ADHD as a “disorder or brain maturation delay” and said structural differences were greatest for children. In adults, there were no significant differences between those with ADHD and the control group.