What does brain imaging tell us about ADHD?

We now are able to look at the brain in ways that show its development and function. Studies have shown that kids with ADHD have smaller brains than kids without ADHD. This does not correlate with the head size your doctor measures in infancy, and head size does not help physicians predict ADHD.

Last week’s post What is ADHD? Why do some develop it? introduced the concept that ADHD is a brain disorder, not a problem with parenting or other common misbeliefs. Today we’ll go more in depth into how brain imaging has shown differences when people have ADHD. Next week we’ll go further into the genetics of it. 

Brain imaging

There are many ways we can image the brain for different reasons. Single-photon emission computer tomography (SPECT), positron emission tomography (PET), and functional magnetic resonance imaging (fMRI) are all being studied to show different aspects of brain function and development.

Some of the studies look at blood flow to various parts of the brain during different tasks to show which parts of the brain are triggered and how that differences among different groups of people. Others look at subtle changes in brain growth.

With vs without ADHD

Brain imaging comparing large groups of kids with ADHD to those without ADHD show significant differences. These are very subtle differences and are still considered investigational. The changes are too subtle to diagnose ADHD in any one person.

There are several areas of the brain that have been shown to be smaller in children with ADHD. At this time the specific areas of delayed growth do not correlate with specific treatments.

ADHD is a brain condition

It is not recommended to do imaging studies to diagnose ADHD, but the fact that large groups of people show differences highlights the fact that ADHD is a real disorder of the brain.

Hopefully as this information is recognized, the stigma of ADHD and other brain disorders will be lost. People will be able to understand that it is a real brain dysfunction.

The case for a clinical diagnosis

Studying brain differences helps us to understand ADHD, but imaging is less useful to any individual for diagnosis. We have a good track record for diagnosing ADHD with standardized questions and a clinical history.

Images capture a moment in time, but they don’t necessarily tell the whole story.

What happens to a brain in different circumstances? It can be very insightful to ask what happens when a child is doing a favorite activity versus when he’s stressed.

Clinical history can cover different situations over time. This cannot be captured in any brain image.

To be useful for diagnosis and management of a medical condition, a test must first:

  • Be reliable: The changes seen are very subtle, and results must be shown to be accessible and identifiable in individuals to be useful for diagnosis. If only a few trained people can identify the subtle differences, it will not be available or helpful to most people. 
  • Show safety: Everything we do in healthcare must be shown to be safe and effective before it’s used. Risks and benefits must be weighed. Risks of imaging must be considered.
  • Show benefit: If a clinical diagnosis can be made, what benefit would be attained by doing an expensive test? If it does not add to the treatment, it should not be done. Since the large majority of people with ADHD can be diagnosed clinically, we should not need to do studies that add risk and cost.

Back to the prefrontal cortex…

In What is ADHD? Why do some develop it? I mentioned that the prefrontal cortex and said that it was especially interesting. Let’s talk more about why.

Brain lobes serve different functions.  Learn more at www.adhdkcteen.com. #adhd #adhdkcteen #development

Studies have shown that the prefrontal cortex develops more slowly in children and teens with ADHD. This means that the areas of the brain that control executive functioning are thinner in children with ADHD versus those without ADHD.

Functional imaging shows that the frontal lobes in children function less during activities involving concentration, memory, decision-making and problem solving.

It’s even more than that. Those with worse outcomes as they mature have fixed thinning (it doesn’t ever normalize) but those who ultimately develop a normal thickness have a better outcome. 

A thinner brain cortex is not a damaged brain. It is an alteration in development.

Other parts of the brain are affected too

Our cerebellum helps us with movement and memory. Children with ADHD show slower growth of cerebellar white matter in early childhood, but faster growth in late childhood. 

The amygdala and hippocampus are also smaller in the brains of people with ADHD. These areas are responsible for emotional processing and impulsivity, problem areas for many with ADHD.

What does all of this mean?

You guessed it: it’s still being studied.

Studies continue to help us learn more about brain structure and function. We also continue to learn about the chemical interactions that happen while our brain is working. 

What all this information means and how we can use it to best manage the troubling symptoms of ADHD is yet to be fully uncovered.

It may be possible one day to predict which children will develop ADHD and change something in the early years to alter that development. But we’re not there yet…

Does a slower development of certain brain areas have an advantage? Maybe the slower development of the cerebellum is why kids with ADHD learn better when they fidget.

These are the things we still need to learn.

We don’t really know the full extent of it yet.

For more:

ADHD Neuroimaging: What’s New?

Coming up next:

What do we know about the genetics of ADHD?

What is ADHD? Why do some develop it?

ADHD was first recognized as a behavior problem, but now we know it’s a developmental disorder. Don’t worry though. Having a developmental disorder doesn’t make you stupid or damaged. It simply means that brain development is a bit different. We’ll tackle details here.

Typical Brain Development

Our brains have billions of nerve cells called neurons that start developing a few weeks after conception. Within 6 months after conception, there are even more neurons than are found in an adult brain. As we develop, neurons grow and make connections with one another. The number of brain cells decrease as unneeded neurons are pruned away.

Neurotransmitters help to communicate from one neuron to another. For more see adhdkcteen.com. #adhd #whatisadhd #braindevelopment

A network of fibers develops to connect the brain cells in order to interact with other parts of the brain and to perform complex functions. Neurotransmitters help send messages between nerve cells.

We’ll tackle neurotransmitters more in future posts. They’re important!

How long does it take for the brain to fully develop?

We might look pretty mature by our teen years, but our brain is still growing!

The first 3-4 years of life is a time of rapid brain development, but it continues for more than 20 years.

Brains don't stop growing when we do. Learn more at www.adhdkcteen.com. #adhd #adhdkcteen

Prefrontal cortex

The prefrontal cortex is especially interesting. It helps us plan, organize, make decisions, and maintain self control. These are considered executive functions and are often problematic for those with ADHD.

The prefrontal cortex typically doesn’t finish full development until mid-20s. That means our brains are still developing key areas into our early adult years!

For a fun interactive way to see all areas of the brain, visit Brainfacts.org.
For a fun interactive way to see all areas of the brain, visit Brainfacts.org.

How does ADHD develop?

There are many things that affect our brain development that can lead to symptoms of ADHD.

At this point we don’t diagnose the cause of the ADHD since treatment is geared toward addressing the symptoms, but it can be helpful to know that there are many reasons a person develops ADHD.


Like many things, brain development is affected by our genetics. Genetics affects how we look, how tall we should grow, our intelligence, and risks of certain health problems – such as cancer or heart disease. Of course our genetics are only the blueprint. Our environment, nutrition, experiences, and much more also affect how we grow and develop.

If one parent has ADHD, a child is more likely to have ADHD. If both parents have ADHD, their child is much more likely to have ADHD.

Genes can affect whether or not we develop ADHD. Learn more at www.adhdkcteen.com. #adhd #adhdkcteen

Prenatal development

While a baby is still in its mother’s womb, it is considered a fetus. This is considered the prenatal time of development.

Many things can affect development during the prenatal time. Drugs and alcohol, illness, and other stressors affecting the mother can affect the baby.

Prematurity (being born before the due date) and being small at birth can increase the risk of developmental disorders, including ADHD.

Our brains develop for months before we're born. Learn more at www.adhdkcteen.com. #adhd #adhdkcteen #development

Illness, injury, toxins and more… oh, my!

The first few years of a child’s life can be complicated by illness, injury, nutritional deficiencies, and toxins. These can all affect brain development.

Even after the critical developmental years, injuries and toxins to the brain can change our brain function. Think of a teen or adult who has had a concussion. Their brain function can be severely altered. They might suffer from mental fogginess, fatigue, irritability, and more after the injury. In fact, sometimes people will be treated with medications commonly used for ADHD temporarily after a concussion. 

What it’s NOT:

ADHD is not due to bad parenting, poor discipline, or bad schools. 

ADHD is not from bad parenting. It is based in our brains and is neurological. For more see adhdkcteen.com. #adhd #whatisadhd #braindevelopment

Yes, those things can worsen a child’s behavior, but they don’t cause ADHD.

What about sugar?

ADHD also isn’t from too much sugar.

Studies have even shown that even when a parent perceives worsening of behavior after sugar, independent observers see no real change. For more on that and how diets affect ADHD, see Special Diets for ADHD.

There are many myths about why ADHD exists - and some even deny its existance. Learn the real cause of ADHD. #adhdkcteen #adhd

Coming up…

Tune in next week for information on brain imaging in ADHD that shows specific differences in the ADHD brain and then for information on what we know about the genetics of ADHD!