The ADHD Vs. Non-ADHD Brain: What Are The Differences?

ADHD VS. Non-ADHD Brain: Comparison Table

ADHD Brain Structure

The ADHD brain is structured differently from a neurotypical brain. A study found that people with ADHD have smaller brains, and the prefrontal cortex develops more slowly.¹ Other studies have shown that deeper areas of the ADHD brain can also be affected, leading to ADHD symptoms.

It is important to note that a smaller brain does not impact intelligence; it just means that someone with ADHD functions differently than someone with a neurotypical brain. People with ADHD are considered neurodivergent, which means that their ways of thinking, remembering, and behavior are different, but can function well in society. In terms of brain size, ADHD brains are a tiny percentage smaller than non-ADHD brains. These differences are not clearly detected with an MRI but are evaluated with computer calculations.

The four regions of the brain impacted by ADHD are:

Prefrontal Cortex (PFC)

Studies show that those with ADHD have weaker prefrontal cortex (PFC) functioning, especially in the right hemisphere.² The PFC is responsible for attention, behavior regulation, decision-making, memory, and emotion control.

Working memory involves the capacity to hold recent events in mind, recall information from long-term memory, and implement this knowledge to control behavior, thinking, and emotions. The PFC does this by having intricate connections with different areas of the brain.¹¹ The right hemisphere is also responsible for behavior inhibition. Because those with ADHD have weaker functions in the right hemisphere of the brain, they can struggle with impulsivity, trouble focusing, and emotional dysregulation.

The PFC, along with other parts of the brain, controls executive functioning, which has seven components: time management, adaptable thinking, planning, self-monitoring, self-control, working memory, and time management. People with ADHD struggle with these components due to the changes in the PFC and suffer from executive dysfunction, making these tasks more difficult to complete, thus impacting their occupational and social functioning at times.³

Common ADHD symptoms linked to prefrontal cortex differences include:

• Struggling to pay attention
• Time blindness
•  Distractibility
• Trouble regulating emotions
•  Inability to multitask

Limbic System

The limbic system has four parts: amygdala, hippocampus, thalamus, and hypothalamus. It is responsible for emotional responses and regulation related to survival,  such as your stress response or “fight or flight.” The amygdala controls the fear responses, input, and context of emotions, and the hippocampus stores and retrieves memories.⁴ They work together to translate these emotions into specific responses.

ADHD-related changes may result in:

• Emotional outbursts
• Hypersensitivity, including rejection sensitive dysphoria

ADHD symptoms due to differences in the limbic system include:

• Trouble regulating emotions
• Moodiness
• Low self-esteem
• Irritability
• Sleep changes

Basal Ganglia

Among the basal ganglia are two sections: caudate and putamen. The caudate region is deep inside the brain and controls movement and behavior, memory, reward, and motivation, all of which can be impacted by ADHD.⁶ The putamen is involved with movement and learning, language, cognitive function, and articulated speech, which can also be impacted by ADHD.⁷

The basal ganglia manage motor learning, such as learning a skill by practicing the steps  and the order of steps. Information flows through the basal ganglia to the cortex to help with motor control.¹² One study showed that boys with ADHD had significantly smaller basal ganglia.⁵ Dysfunction in the basal ganglia can lead to inattention or impulsivity.

ADHD symptoms due to differences in the basal ganglia include:

• Difficulty prioritizing tasks
• Impulsivity
• Hyperactivity
• Poor planning
• Forgetfulness

Reticular Activating System

The reticular activating system (RAS) is a network of neurons that manages the sleep/wake cycle, plays a part in fight or flight responses, and can also control our ability to focus. In ADHD, the RAS is dysregulated and can cause ADHD sleep issues. It can also impact how individuals perceive the world. People with ADHD often stay up later and sleep in later because the circadian rhythm is misaligned.

ADHD symptoms due to differences in the RAS include:

•  Impulsiveness
• Going to sleep late
• ADHD insomnia
• Trouble concentrating
• Inattention
• Hyperactivity

ADHD Brain Function

Brain function is measured by three main tests: functional Magnetic Resonance Imaging (fMRI), magnetoencephalography (MEG), and electroencephalography (EEG).⁸ These tests show that people with ADHD have less blood flow to certain areas of the brain, such as the prefrontal cortex.⁹ EEG is typically used clinically in epilepsy management, and it is considered a research tool in the context of ADHD.¹³

Those with ADHD tend to have problems with functional brain connectivity or how the areas of the brain communicate with each other. The differences in functional brain connectivity are responsible for many of the common symptoms of ADHD, such as hyperactivity.

ADHD Brain Chemistry

ADHD brains also have different brain chemistry. There is an imbalance in the neurotransmitters, which are chemicals that carry messages from one cell to another. Dopamine, norepinephrine, GABA, and serotonin are the primary neurotransmitters affected by ADHD. Differences may be due to a lack of certain neurotransmitters, insufficient receptors, or the body processing them incorrectly.

Neurotransmitters that differ in the ADHD brain include:

Dopamine

Dopamine allows us to feel pleasure, motivation, and satisfaction. People with ADHD may have low dopamine levels, causing them to seek “ADHD dopamine hits” or ways to get instant gratification to feel “good” and as if they have achieved something. This can lead to extreme distractibility of ADHD hyperfixation, a narrow and rigid focus on a task, because of the surge of dopamine from the feeling of accomplishment or novelty.

Norepinephrine

Norepinephrine regulates stress reactions, attention, arousal, and cognitive function. People with ADHD have low levels of norepinephrine, which can cause depression, chronic fatigue, and low mood. Low norepinephrine can cause ADHD sleep issues, anxiety, and low blood pressure.

Serotonin

Serotonin is a neurotransmitter that manages happiness, optimism, and mood. When serotonin is higher, it can help ease hyperactivity in ADHD by creating a calming effect.

How Is ADHD Diagnosed?

ADHD is diagnosed in accordance with the DSM-5 criteria using clinical interviews and assessments. A clinical psychologist, physician, or psychiatrist usually diagnoses ADHD. In some states, clinical social workers, counselors, and other licensed mental health professionals with advanced training can diagnose ADHD.

To receive an ADHD diagnosis, there must be a persistent pattern of hyperactivity and/or inattention for at least six months.⁹ To diagnose a child with ADHD, six or more ADHD symptoms must be present, while an adult with ADHD has to have five symptoms or more.

Can ADHD Be Diagnosed Using A Brain Scan?

Brain imaging is not a diagnostic tool for ADHD. A functional Magnetic Resonance Imaging (fMRI) shows an image of the brain with different colors based on activity for different specific functions, like language. A Positron emission tomography (PET) scan shows brain tissues and cell abnormalities. An electroencephalography (EEG) measures brain waves and can be a tool to diagnose ADHD in conjunction with clinical interviews and assessments.

How Is ADHD Treated?

ADHD cannot be cured, but there are ways to better understand and manage the symptoms. ADHD is most often treated with medication, lifestyle changes, and therapy. Stimulants are the most prescribed medications. Lifestyle changes may include adding supplements, increasing your support network, and learning about your unique symptoms.

Treatments options for ADHD include:

• Cognitive behavioral therapy (CBT): CBT for ADHD is a form of behavioral therapy that replaces unwanted thoughts with healthier ones and teaches time management and organization skills.
• Medication: Medication for ADHD  falls into two categories: stimulants and non-stimulants. Stimulants increase dopamine and norephedrine and are fast acting. Non-stimulants also increase norepinephrine and can be longer acting.
• Natural remedies: Natural remedies for ADHD are also an option for treatment. They include therapy, lifestyle changes, supplements, and mindfulness to help manage and understand symptoms.
• Family therapy: ADHD can affect the whole family unit. Family therapy can help parents and siblings better understand symptoms and how to manage them appropriately.
• Parent skills training: This can help parents better understand how to manage symptoms and responses to manage or guide behaviors.

How to Find Professional Support

If your symptoms impact your functioning, that’s a sign it’s time to reach out and get more help. It’s important to find a professional you trust and who understands ADHD. To find a neurodiverse-affirming therapist, check their training and licensure using an online therapist directory to see if someone has advanced training in this area. If in-person therapy feels overwhelming, online psychiatrist options can help you get assessed via telehealth, and online therapy platforms can assist you in obtaining care wherever and whenever you need it.