There are differences between the brain development, structure, and function of people who have ADHD and people without ADHD. These differences are key to understanding and treating some of the common ADHD symptoms and behavior patterns.

Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental condition that causes differences in the brain related to attention, behavior, and activity levels, including impulsivity and hyperactivity.

Read on to learn more about the differences between the brain of a person with ADHD and the brain of a neurotypical person, as well as how to diagnose ADHD.

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There are several differences between the brains of people with ADHD and people without the condition. ADHD causes differences in:

  • brain structure
  • brain function
  • brain development

These differences relate to brain size, neurotransmitters, and brain networks. People with ADHD may have areas of the brain that mature more slowly or have different activity levels than a neurotypical brain. Some brain differences may change as a child matures and grows older.

The brain maturation process varies by the child’s developmental stage. According to older research, the process includes:

  • the careful growth, positioning, and organization of neurons (the brain’s cellular units of communication) into working brain networks
  • the development of myelin around neurons, which provide efficient neuronal transmission
  • the pruning, or re-organization, of unnecessary or inefficient neuronal circuits

ADHD affects brain functioning in several ways. The condition has links to abnormal cognitive, behavioral, and motivational functioning. ADHD can affect the regulation of moods, emotions, and brain cell connections. It can also affect communication between different areas of the brain.

Brain networks are groups of nerve cells, called neurons, which send information throughout the brain. The brain networks of people with ADHD may take more time to develop and be less effective at relaying certain messages, behaviors, or information. These brain networks may function differently in areas such as focus, movement, and reward.

Imaging tools such as those based on MRIs and X-rays can measure subtle abnormalities in the structure and the function of the brains of people with neurodevelopmental disorders, including ADHD. In imaging studies of people with ADHD, there is an imbalance in the way that some brain networks are structured, which is called structural connectivity. There is also an imbalance in the way that some brain networks function, which is called functional connectivity.

In studies designed to induce a specific brain function, such as a challenging thought-related task, or an emotion-inducing situation, researchers and scientists can look at the pattern of activity across different brain regions in people with ADHD and compare them with neurotypical individuals in order to find out how their brains differ.

Research shows that in people with ADHD, some brain regions become “hyperactive,” whereas other brain regions are “hypoactive.” This suggests that there may be a problem with the brain’s computing capacity to appropriately meet the cognitive demand of the task.

For example, a person with ADHD may be unable to suppress brain activity in the default attention network, especially as a task becomes more difficult. This may link to more distractibility.

A 2019 study used resting-state functional MRIs to observe the brain circuity in adults with ADHD. Researchers linked increases in functional connectivity in certain brain regions to clinical symptoms of hyperactivity and restlessness, suggesting that inefficiencies in brain network processing could explain some symptoms of ADHD.

ADHD can affect executive functioning skills related to the following:

  • attention
  • focus
  • concentration
  • memory
  • impulsivity
  • hyperactivity
  • organization
  • social skills
  • decision-making
  • planning
  • motivation
  • task-switching
  • learning from past mistakes

There are several differences between the brain structures of people with and without ADHD. These differences affect several areas of the brain that relate to common ADHD symptoms.

A 2017 study suggests that compared with children without ADHD, children with ADHD often have slightly smaller brains, and their brains may take more time to mature. Volume differences often exist in various brain regions, including the amygdala and hippocampus, which relate to motivation, memory, and emotion regulation. It’s important to note that brain size does not affect intelligence.

According to a 2007 publication from the National Institutes of Health, children with ADHD have delayed brain maturation in certain areas. The most prominent delays were at the front of the cortex, which relates to cognitive, attention, and planning control. The motor cortex was the only brain region that matured quicker than usual in children with ADHD, which may relate to symptoms such as restlessness and fidgeting.

The frontal lobe controls cognitive functioning such as attention, impulse control, and social behavior. Certain areas of the frontal lobe may mature more slowly in people with ADHD. This delay may cause dysfunction related to these cognitive skills.

The premotor cortex and prefrontal cortex are parts of the frontal lobe involved in motor activity and attentional capacity. These areas of the brain may have less activity in people with ADHD.

Often, people show ADHD symptoms at a young age, though it’s possible to exhibit symptoms later in life. Usually, a person receives an ADHD diagnosis when they are a child. To receive an ADHD diagnosis as an adolescent or adult, the person must have displayed symptoms before age 12.

To diagnose ADHD, a psychiatrist, psychologist, or psychotherapist who specializes in ADHD will evaluate the person using a variety of methods, including behavior and symptom checklists or tests. The evaluation may also involve interviews and observations from teachers, parents, or family members.

To receive an ADHD diagnosis, the person must display chronic or long-lasting symptoms related to attention, hyperactivity, or impulsivity. The symptoms must negatively affect the functioning and development of the person. The doctor will rule out the possibility of other causes of ADHD symptoms, such as a different medical or psychiatric condition.

ADHD diagnosis may involve brain scans that measure brain activity and blood flow, including:

  • functional MRI
  • single-photon emission computed tomography
  • PET scan
  • Neuropsychiatric EEG-Based Assessment Aid System

Learn more about ADHD misdiagnosis here.

It is important to note that while ADHD presents numerous challenges, there are also some possible benefits people with the condition may experience. Learn about them here.

ADHD is a neurodevelopmental disorder that causes differences in brain growth, development, and function.

ADHD can also cause delayed maturation and activity differences in certain brain regions. The differences of the ADHD brain can affect thinking, behavior, and emotions.

Doctors often diagnose ADHD in children who demonstrate these brain differences and common symptoms. ADHD is a treatable condition, and sometimes symptoms ease with age. Treating ADHD often helps improve quality of life and academic performance.