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The Physical Differences of an ADHD Brain


For some reason, people are still debating the validity of Attention Deficit Hyperactive Disorder. So many people (with no harm intended) still believe that ADHD is an emotional disorder of some sort, rather than a physical difference in the brain.

In the same way that depressed brains release different chemicals and function differently, ADHD brains also operate in different ways than non-ADHD brains. Not only do they function differently, but they’re created differently.

I want to shed some light on the physical differences between an ADHD brain and a non-ADHD brain. This list doesn’t compile all the differences (and science still has so much left to discover about ADHD and the human brain), but it’s the most widely recognized points.

I’ve broken them down into parts and tried to make them more reader-friendly than the doctor reports you might receive right after diagnosis.

[Note: Some of these points are still being debated by scholars, but for the most part, they’re all thoroughly back by the medical/psychological community.]

1. Slightly smaller brains overall

Studies have shown that children with ADHD typically have brains that are 5% smaller (on average) than brains without ADHD. Their brains don’t usually end up smaller, but they are slower to grow. This means that, at any given point in adolescence, if you measure an ADHD brain against a non-ADHD brain of the same age, you’ll usually find that the ADHD brain is slightly smaller.

This explains why some children with ADHD have the maturity level of a younger child.

By adulthood, however, most ADHD brains catch up in size and finish fully forming, which is why some kids eventually “outgrow” ADHD.

2. Lower levels of dopamine in the brain

According to, dopamine is, “a … neurotransmitter … acting within the brain to help regulate movement and emotion.”

Psychology Today explains that “dopamine neurons become activated when something good happens unexpectedly, such as the sudden availability of food.”

In other words, dopamine neurons turn on when exciting things happen, which makes a person feel good. This feeds into the person’s reward system, making them eager to feel that positive sensation again. It’s similar to how drug addicts feel a high (or rush of dopamine levels) and then seek to reach that high over and over again.

The difference for people with ADHD, however, is that it takes a lot more excitement to give them that sensation of being rewarded because their dopamine levels are so much lower. They have less neurons available for activation, so it takes bigger, more immediate excitement for them to become interested.

This is why simple reward/discipline scenarios aren’t always as effective with ADHD kids. They don’t feel a sense of reward or gratification when they’ve pleased a parent (like most kids do) because that’s not a big enough deal to activate their dopamine neurons.

These lower levels of dopamine are also a huge factor in why a lot of kids with ADHD are so attracted to video games. Video games offer a lot of stimulation and positive rewards—which activate the dopamine neurons in their brains—so they enjoy the feeling they get when playing.

The fact that they enjoy it so much just reinforces their desire to reach those levels of dopamine again. They don’t get that type of reward from conversation or parental affirmation or stickers on a chart because those are only mild dopamine triggers.

It might work for other kids, but not necessarily for kids with ADHD.

Have you ever wondered why people with ADHD can hone in on their favorite TV show, completely forgetting everything else exists, but they can’t stay focused on a conversation for more than ten seconds? This is part of the reason why. The dopamine rewards and reinforcements have to be big enough to draw them in.

You might have noticed that the dictionary definition of “dopamine” also stated that it effects movement. Higher levels of dopamine can mean greater control of movement, while lower levels can mean weaker control of movement. Most kids with the hyperactive form of ADHD (because of their lower dopamine levels) don’t have as much control over their movement as they’d like, which means they end up sort of bouncing off the walls.

(Fact: Low dopamine levels have been found in patients with Parkinson’s Disease, which causes loss of motor control and spastic movement from them.)

3. Thinner frontal cortex of the brain with slower maturation of the cortex

The frontal cortex of the brain controls things like judgment, decision-making, planning, attention span, and inhibition. Because the frontal cortex is thinner in a lot of ADHD brains, those abilities don’t come as easily to them.

And because the cortex is slower to mature, those abilities can take longer to master. This is why impulsiveness is such an issue for most ADHD children. They literally don’t have the capability of stopping to think before they act.

4. Faster maturation of motor cortex

The motor cortex of the brain controls the execution of movement. Since some children with ADHD have faster-maturing motor cortexes, their brains tell their bodies they need to execute more movement than is really necessary. This explains why children with the hyperactive form of ADHD (as opposed to the inattentive type of ADHD) feel the need to be in constant motion. Their brains are telling them to move.

It also explains why a lot of children with Hyperactive ADHD are so much more physically adept than their peers. They learn to walk sooner, run sooner, climb sooner, pedal a bike sooner, and so and on and so forth. That’s not always the case, but many times it is. This means that their brains pick up physical movements and muscle memory sooner, causing them to become more physically skilled sooner than their peers.


Do you have any points to add? What have you learned in your research about ADHD? What have your doctors explained?

We’d love to hear from some experts on the subject, too.

Thanks for reading, and please reach out to us if you have any questions, concerns, or comments!

The Physical Differences of an ADHD Brain

W. R. Cummings

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APA Reference
Cummings, W. (2016). The Physical Differences of an ADHD Brain. Psych Central. Retrieved on March 30, 2020, from


Last updated: 10 Feb 2016
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