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Key takeaways
- ADHD is characterized by differences in brain structure, such as smaller brain volumes and areas that mature at a slower rate.
- ADHD shows reduced blood flow to areas of the brain responsible for tasks such as attention and planning, highlighting differences in function.
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder. This means that ADHD has differences in the brain that affect a child’s development. ADHD does not affect intelligence. However, it affects a person’s ability to focus and regulate emotions, and results in hyperactivity and impulsivity, as well as organizational problems.
Although it is classified as a condition, more recent thinking sees it as a form of neurodiversity. People with ADHD report brain processes differently, but this represents a normal variation rather than a disorder that needs to be ‘treated’. This approach to neurodiversity emphasizes recognizing these differences and valuing strengths rather than focusing only on challenges or deficits.
Rather than trying to change the characteristics of ADHD to fit a neurotypical world, this approach emphasizes the importance of accommodations and supports to help people thrive.
Differences in the ADHD brain
ADHD has come under much scrutiny over the past few decades, leading to increased public misconceptions and stigma. In the past, some critics questioned whether this was real or attributed it to lack of motivation, willpower or poor parenting. After that, there was an explosion of stories suggesting that ADHD was overdiagnosed and overmedicated.
Of course, none of these are true, but if you or your child has ADHD, you may feel undermined by these types of comments.
Knowing that there are biological differences in the ADHD brain—compared to the brain of a person who does not have ADHD—can be validating for someone dealing with the condition, as it provides additional evidence of the realities of ADHD.
The differences can be divided into three areas: structure, function and chemistry.
Watch now: Strategies for Living Well with ADHD
Structure of the ADHD versus non-ADHD brain
Years of research have shown clear structural differences in the ADHD brain. The largest review of brain scans of ADHD patients was conducted at Radboud University Nijmegen Medical Center and published in 2018.
Research has found that people with ADHD have smaller brain volumes in five subregions and a smaller total brain size. These differences were more prominent in children and less prominent in adults.
Parts of the ADHD brain mature at a slower rate (about one to three years) and may not fully reach the level of brain maturity without ADHD.
Another important finding was that people with ADHD have smaller amygdala and hippocampus. These regions are involved in emotional processing and impulsivity and were previously not specifically linked to ADHD.K
ADHD versus non-ADHD brain function
Researchers use several brain imaging techniques to study how the ADHD brain works and functions, including:
- Functional Magnetic Resonance Imaging (fMRI)
- Positron Emission Tomography (PET)
- Single Photon Emission Computed Tomography (SPECT)
In people with ADHD, blood flow to certain areas of the brain, such as the prefrontal regions, is altered compared to people without ADHD. Decreased blood flow to these areas suggests reduced brain activity.
The prefrontal area manages executive functions, which are responsible for tasks such as planning, organizing, paying attention, remembering, and regulating emotions.
Research suggests that ADHD may be linked to abnormal brain connectivity. Studies with resting-state MRIs suggest increased connectivity in certain brain regions in individuals with ADHD.
Research has found that children with ADHD do not have the same connection between the frontal cortex and the visual processing area of the brain. This suggests that ADHD brains process information differently than non-ADHD brains.
ADHD versus non-ADHD brain chemistry
The brain functions as a communication network where messages are passed from one neuron (brain cell) to another. Between neurons is a gap called a synapse, which must be filled with a substance called a neurotransmitter to transmit messages.
The key neurotransmitters for ADHD are dopamine and noradrenaline. ADHD is a dysregulation of the dopamine system in the brain. For example, there is either too little dopamine, not enough receptors for it, or the dopamine is not being used efficiently.
Stimulant drugs help ADHD because they encourage more dopamine to be produced or keep dopamine in the synapses longer.
How is ADHD diagnosed?
A brain scan cannot be used to diagnose ADHD. There is no objective test to diagnose ADHD. A diagnosis of ADHD requires a thorough evaluation by a qualified physician, psychiatrist, or psychologist. Assessments include:
- An in-depth interview with the patient
- Review of school reports and medical history
- Tests to measure attention, distraction and memory
While PET and fMRI scans can be useful for research, they really only provide insight into how the brain is working at the time the test is performed. Brain scans do not take into account how the brain works in different situations, unlike clinical tests during a detailed interview.
In addition, the scan data that have been studied are usually based on group averages and are not applicable to any particular individual. Results have not been normalized, which occurs when large amounts of data are collected and compared.
ADHD is diagnosed as a neurodevelopmental condition, but it is important to remember that it represents a common variation in brain structure, function, and chemistry. These differences can create challenges in your life, but that doesn’t mean they’re something that needs to be “cured.” ADHD also comes with strengths.
Understanding the underlying causes of your ADHD traits can be validating and gives you a place to start when it comes to managing some of the challenges you’ll experience living in a society designed for neurotypical brains. Getting an accurate diagnosis is a great place to start. Depending on your unique experience, you may find that medication, therapy, ADHD coaching, housing, and social support can help.
