Neuroscience of ADHD

The Neuroscience of ADHD

Attention-Deficit/Hyperactivity Disorder, commonly known by its acronym ADHD, is a condition frequently encountered in neuropsychology. Common symptoms include short attention span, excess activity, and behavior with little thought for consequences. Though typically diagnosed at its usual onset in early childhood (3-6 years old), these symptoms can last into adulthood (around 30-50% of those diagnosed as children) though some may outgrow it. Given the relatively high prevalence of ADHD and its social ramifications, we’re going to delve a little deeper into the neuroscience of this disorder.

Symptoms, Subtypes, and Associated Conditions

Most people with ADHD have issues with goal-oriented behaviors, for example – paying attention, staying focused, and seeing tasks through to finish. Other symptoms can include anger management issues and poor handwriting (dygraphia).

Nonetheless, there are three subtypes of ADHD each defined by their primary symptoms.

The Inattentive Subtype causes patients to be distracted and forgetful, losing track of time and having a hard time focusing on tasks. Girls are more likely to have this subtype.

Those with the Hyperactive Subtype are impulsive, fidgety, impatient, have a hard time controlling impulses, and are very talkative. Adults with this subtype can appear as having an inner restlessness rather than outward movement.

Lastly, the Combined Subtype has both inattentive and hyperactive-impulsive symptoms.

Other conditions that can be diagnosed alongside ADHD include epilepsy, Tourette’s symptom, Obsessive-Compulsive Disorder, and autism.

Prevalence and Causes (Genetic and Environmental)

ADHD is found in about 5% of children and 2-3 times more likely in boys than girls, though this may be partially related to difficulty diagnosing girls due to social expectations surrounding female behavior. It’s not completely clear what causes ADHD, but there is evidence for a genetic relationship.

For example, siblings are 3-4 times more likely to have the condition compared to families without it. Furthermore, other studies show that patients with ADHD have common deficits in neurotransmitters, which are the chemical substances involved in the transmission of nervous system signals.

The specific neurotransmitter deficit in ADHD is widely thought to be related to dopamine and norepinephrine. Dopamine is typically known as the “reward molecule” of the brain involved in pleasure, dopamine is also involved in decision-making, movement, and motivation.

Environmental factors such as Fetal Alcohol Syndrome, exposure to certain chemicals, and particular infections such as measles during pregnancy or early childhood have been found to contribute to an ADHD diagnosis or at minimum similar symptoms.

fMRI Research Evidence on Brain Changes

ADHD has been well-studied for quite some time. For example, meta-analysis of large fMRI research experiments, which studies brain activation by measuring bloodflow, has revealed brain changes in many regions:

  • There is reduced activation in the right dorsal attention network, which could play a key part in the inattentive subtype.

 

  • One of the most prominent changes especially in the hyperactive-impulsive subtype is reduced activation in the inferior fronto-striatal circuit during motor-inhibition tasks, meaning that children with ADHD have less activation in this region that prevents motion; other areas of decreased brain activation related to movement control include the supplementary motor area, anterior cingulate cortex, right striatum, and left thalamus.

In general, most brain changes in those with ADHD involve decreased signaling in circuits that allow for controlling attention and impulses. Many issues are related to communication between the frontal lobe (the brain’s executive processing center) and the regions related to coordinating various behaviors. It is important to note, however, the limitations of these studies – fMRI does not tell us which neurotransmitters are involved and are focused on children, though adult studies have found similar results.

Treatment Options (Clinical Therapy and Medications)

ADHD is treated in a few different ways. Medication management is highly recommended in cases that school or work is negatively affected by the disorder. These drugs that increase the availability of dopamine and norepinephrine in the brain. Adjunct clinical therapeutic approaches however are crucial and effective for the management of possible emotional dyscontrol and executive dysfunction.

The following are some therapeutic techniques that have proved effective:

  • Cognitive Behavioral Therapy
  • Behavioral Parent Training
  • Cognitive Rehabilitation
  • Executive Function Coaching
  • School Modifications

In our office we start with a detailed assessment and a subsequent development of specific treatment plan that includes all or a set of the therapeutic techniques depending on the case. No brain is the same and it should not be treated as such!

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