9 Neurological Differences In People With ADHD

Written By Esther Roberts

During the process of my son’s ADHD diagnosis and then my own, I have looked long and hard for a concise and clinically proven summary of the core differences in wiring in people who have ADHD. Edward Hallowell’s book ADHD 2.0 provides the most comprehensive overview and I have read many studies that speak to these neurological differences, but never in a super simple, easy to digest format. So, I have created the list below to provide details of the top 9 differences and how these can present behavivourly in children and adults with ADHD.

1.Reduced Dopamine Activity

Dopamine dysregulation in people with ADHD leads to difficulty with reward-based motivation and sustained focus.

  • Behaviours:

    • Difficulty sustaining attention on low-stimulation or long-term tasks.

    • Inability to stay motivated without immediate rewards.

    • Increased likelihood of procrastination or task avoidance.

    • Seeking high-stimulation activities, such as video games or social media, to boost dopamine.

    • Struggling with reward-based decision-making, often acting impulsively.

  • Clinical Study: Volkow, N. D., et al. (2009). "Evaluating Dopamine Reward Pathway in ADHD: Clinical Implications." The Journal of the American Medical Association. 

2. Impaired Executive Functioning

Executive dysfunction impacts planning, organising, decision-making, and impulse control, often causing individuals with ADHD to feel overwhelmed.

  • Behaviours:

    • Difficulty organising tasks and managing time effectively.

    • Frequent forgetfulness or losing items.

    • Trouble prioritising tasks, leading to overwhelm.

    • Struggling with impulse control, resulting in interruptions or impulsive actions.

    • Difficulty starting or completing tasks that require long-term planning.

  • Clinical Study: Willcutt, E. G., et al. (2005). "Neuropsychological Performance of ADHD Subtypes: Implications for Executive Functioning." Journal of Abnormal Psychology

3. Altered Prefrontal Cortex Activity

Reduced prefrontal cortex activity in those with ADHD means clients may struggle with sustained attention, focusing, and impulse control.

  • Behaviours:

    • Inability to sustain attention on tasks that require mental effort.

    • Difficulty controlling impulses or delaying gratification.

    • Trouble with problem-solving or decision-making under stress.

    • Becoming easily distracted by external stimuli.

    • Struggling to maintain focus during conversations or tasks.

  • Clinical Study: Barkley, R. A. (1997). "Behavioural Inhibition, Sustained Attention, and Executive Functions: Constructing a Unifying Theory of ADHD." Psychological Bulletin.

4. Smaller Brain Volume in Certain Regions

Differences in brain volume, particularly in the prefrontal cortex, basal ganglia, and cerebellum, can affect attention, motor control, and emotional regulation.

  • Behaviours:

    • Difficulty regulating emotions or impulsive behaviour.

    • Problems with motor control, such as fidgeting or hyperactivity.

    • Shorter attention span, especially in tasks requiring focus.

    • Struggling with fine motor skills, such as handwriting.

    • Emotional dysregulation, leading to mood swings or irritability.

  • Clinical Study: Hoogman, M., et al. (2017). "Brain Imaging of ADHD: Global and Regional Differences in Brain Volume." The Lancet Psychiatry.

5. Differences in the Default Mode Network (DMN)

Persistent activity in the DMN leads to mind-wandering, making it difficult to maintain focus on tasks. In neurotypical individuals the DMN turns off automatically and switches to a separate task orientated brain network when the individual wants to focus on a task, which makes focusing relatively easy. In those with ADHD both networks operate simultaneously creating high levels of mental “noise”, thus making it highly taxing to cut through to a focused state. 

  • Behaviours:

    • Constant mind-wandering, especially during tasks that require focus.

    • Difficulty switching between tasks, leading to distraction.

    • Struggling with mental “noise,” making focused tasks mentally exhausting.

    • Frequently losing track of conversations or tasks.

    • Hyperactivity in the mind, often leading to impulsive or scattered thoughts.

  • Clinical Study: Castellanos, F. X., et al. (2008). "Altered Default Network Connectivity in ADHD." Journal of Neuroscience. 

6. Imbalance in Norepinephrine Activity

Norepinephrine is crucial for maintaining attention and alertness. Dysregulation of this neurotransmitter can make it hard for people with ADHD to stay engaged.

  • Behaviours:

    • Difficulty staying alert or engaged in tasks that require sustained attention.

    • Easily distracted, especially in low-stimulation environments.

    • Experiencing “brain fog” or trouble focusing, especially when tired.

    • Frequent daydreaming or zoning out.

    • Trouble transitioning from one task to another.

  • Clinical Study: Arnsten, A. F. T. (2009). "The Emerging Neurobiology of Attention Deficit Hyperactivity Disorder: The Key Role of the Prefrontal Cortex." Journal of Clinical Psychiatry. 

7. Altered Reward Pathway Sensitivity

A less sensitive reward pathway means people with ADHD often need more immediate, high-stimulation rewards to stay motivated.

  • Behaviours:

    • Needing immediate gratification or rewards to stay motivated.

    • Difficulty completing tasks that don’t offer quick rewards.

    • Tendency to seek out high-stimulation activities (e.g., video games).

    • Poor long-term planning due to focus on immediate rewards.

    • Risk-taking behaviour or impulsive decisions driven by desire for quick rewards.

  • Clinical Study: Tripp, G., & Wickens, J. R. (2009). "Neurobiology of ADHD: Reward Deficiency Syndrome?" Journal of Neural Transmission.

8. Hyperactivity of the Limbic System

Emotional regulation is often difficult for those with ADHD due to an overactive limbic system, leading to impulsivity, emotional outbursts, or stress.

  • Behaviours:

    • Difficulty managing emotions, leading to frequent mood swings.

    • Impulsivity in emotional reactions, such as anger or frustration.

    • Overreaction to stress or criticism.

    • Struggling with emotional regulation, leading to frequent emotional outbursts.

    • Intense feelings of anxiety or restlessness.

  • Clinical Study: Bush, G., et al. (2005). "Attention Deficit Hyperactivity Disorder: Neural Correlates of Emotional Reactivity and Regulation." Biological Psychiatry. 

9. Rejection Sensitive Dysphoria (RSD)

RSD is an intense, negative emotional response to perceived rejection or criticism, which is common in people with ADHD.

  • Behaviours:

    • Intense emotional reaction to perceived rejection or criticism.

    • Avoiding situations that might lead to rejection or failure.

    • Low self-esteem, often tied to fear of being judged.

    • Overanalyzing interactions for signs of rejection.

    • Withdrawal from social situations after feeling criticised or unappreciated.

  • Clinical Study: Dodson, W. W. (2019). "Rejection Sensitive Dysphoria in Adults with ADHD: Understanding Emotional Intensity and Reactions." Journal of Attention Disorders. 

Esther Roberts
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