While attention deficit hyperactivity disorder (ADHD) has long been considered a behavioral disorder, a new study published in The Lancet suggests that it should be considered a neurological disorder, not just a behavioral one. In the largest-ever brain imaging study on ADHD, scientists determined through MRI scans of more than 3,200 people, that the ADHD brain structure is different than the brain structure of those without ADHD.

ADHD Brain Differences

The ADHD brain scans revealed that there are five separate brain regions which tend to be smaller in people with ADHD. While these differences were noticeable in participants of all ages, they were much more dramatic in children. This suggests that as the brains of people with ADHD further develop and mature, these brain regions begin to make up some of the difference.


The amygdala is an almond-shaped structure in the limbic system, which serves as the center for emotions, emotional behavior, and motivation. ADHD brain imaging suggests that this region is smaller in people with attention deficit hyperactivity disorder. This could help explain some of the behavioral symptoms of ADHD.


Also a part of the limbic system, the hippocampus is involved in the storage of long-term memory and plays a large role in learning, memory, and emotion. The study determined that the hippocampus is smaller in people with ADHD, especially as children.

Caudate Nucleus

Like the hippocampus, the caudate nucleus plays a significant role in the way the brain learns. It’s responsible for processing past experiences to influence further action. The study determined that this area of the brain was also smaller in people with ADHD.

The Putamen

The putamen, caudate nucleus, and the nucleus accumbens are all part of the corpus striatum, all of which were shown to be smaller in people with ADHD. The putamen is most involved in the movement of the limbs.

The Nucleus Accumbens

The nucleus accombens is known as the “reward circuit” of the brain and is responsible for processing the neurotransmitter dopamine. The study found that this area was smaller in the ADHD-affected brain.

This ADHD brain scan research suggests that the condition should be treated as a neurological disorder rather than a behavioral one. This development could be especially helpful in combatting a widespread misunderstanding of ADHD as a character flaw, rather than a medical disorder.

For more ADHD health resources, check out the Woodburn Pediatric Clinic Blog. If you still have questions or would like to schedule an appointment, contact us today!