ADHD & Brain Function

The brain of an individual with Attention-Deficit/Hyperactivity Disorder (ADHD) functions differently compared to a neurotypical brain in several key ways:

1. Neurotransmitter Imbalances:

Dopamine and Norepinephrine: ADHD is strongly linked to lower levels or inefficient use of these crucial neurotransmitters, particularly in the prefrontal cortex. These neurotransmitters play vital roles in attention, focus, motivation, impulse control, and executive functions.

Dopamine’s Role: Dopamine is associated with the brain’s reward system, motivation, and motor control. Lower levels or impaired signalling can affect the ability to stay focused and complete tasks, as well as how the brain perceives reward.

Norepinephrine’s Role: Norepinephrine is important for alertness, attention, and the body’s stress response. Imbalances can contribute to inattention and hyperactivity.


Serotonin and Glutamate: Some research suggests that other neurotransmitters like serotonin (mood regulation) and glutamate may also be involved in ADHD.

2. Differences in Brain Activity and Connectivity:

Prefrontal Cortex (PFC) Dysfunction: The PFC, responsible for executive functions like planning, organization, working memory, and impulse control, often shows weaker activation and slower maturation in individuals with ADHD. This can lead to difficulties with these cognitive skills.

Hypoactivity and Hyperactivity in Brain Regions: Some brain regions may be underactive (hypoactive), particularly those involved in attention and executive control, while others might be overactive (hyperactive), such as the default mode network (associated with mind-wandering).

Altered Brain Networks: ADHD is associated with imbalances in the structure (structural connectivity) and function (functional connectivity) of various brain networks involved in attention, reward, planning, task switching, and movement. Communication between different brain regions may also be affected.

Arousal Regulation: The autonomic nervous system, which controls arousal levels, can be dysregulated in ADHD, leading to periods of over- or under-arousal that interfere with focus and regulation.

3. Differences in Motivation and Reward Processing:

Stimulation Seeking: ADHD brains often seek higher levels of stimulation and novelty. They may be less motivated by typical rewards, especially those that are delayed or less intense.

Reward Deficiency: The altered dopamine system can affect how individuals with ADHD experience and respond to rewards, potentially leading to a preference for immediate gratification.


4. Impact on Cognitive Functions:

These functional differences manifest as difficulties in various cognitive areas, including:


Attention: Difficulty sustaining focus, being easily distracted.
* Impulse Control: Acting without thinking, difficulty waiting turns.


Hyperactivity: Excessive movement and restlessness (though this can be less prominent in adults).

Executive Functions: Challenges with planning, organisation, time management, working memory, and emotional regulation.


It’s important to remember that ADHD is a complex neurodevelopmental disorder, and these functional differences can vary in presentation and severity among individuals. Research continues to deepen our understanding of the intricate ways in which the ADHD brain operates.