The Brain And ADHD: Neurotransmitters That May Cause Symptoms

Updated October 07, 2019
Medically Reviewed By: Aaron Horn

ADHD is a neurobiological developmental disorder that affects up to 11% of the US population. Through extensive research in the last few decades, the medical community has learned much about how the brain is affected by ADHD. Neurotransmitters play a key role in the impairment that causes ADHD symptoms. While we still have a long way to go in fully understanding the causes and implications of ADHD, we now know that neurotransmitters are an important piece of the overall brain puzzle.

ADHD can cause widespread ramifications in all areas of a person's life, especially if undiagnosed or untreated. Children and teenagers may struggle with the demands of school, while adults may experience difficulty at work, with maintaining social relationships, or in accomplishing their goals. While some people develop coping strategies to manage their ADHD symptoms, most people will need to seek out professional diagnosis and treatment.

Symptoms Of ADHD

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Attention deficit-hyperactivity disorder (ADHD) is an umbrella term for a condition with three distinct subtypes. These subtypes are primarily-hyperactivity, primarily-inattentive, and the combined type. Each subtype is diagnosed in the presence of a specific cluster of symptoms, as outlined by the DSM-V. ADHD symptoms differ in intensity from person to person and may include:

  • Difficulty focusing
  • Inattention
  • Impulsive behavior
  • Poor working memory
  • Rapid speech
  • Frequent interrupting
  • Impatience
  • Disorganization
  • Difficulty comprehending time

ADHD is thought to develop in the presence of multiple biological and environmental factors. There is a large genetic component to the condition and it appears to run in families. While ADHD is usually diagnosed in childhood, there are many adults who fly under the radar until they run into problems in adulthood.

ADHD is a developmental disorder of the brain and nervous system, meaning that the structure and function of the brain are different than that of a neurotypical person. ADHD symptoms are thought to be caused by differences in the neurotransmitter levels and the way certain parts of the brain function.

What Are Neurotransmitters?

Neurotransmitters are chemicals in the brain that send signals between neurons. These neurochemicals travel inside areas known as synapses. The entire brain is made up of these neurons in an extensive network that controls all of our voluntary and involuntary mental and physical processes.

When a signal is sent to the synapse, neurotransmitters travel from the presynaptic space to a receptor that reads the signal. Each type of neurotransmitter has its own specific receptors on which it acts.

Neurotransmitters Involved In ADHD

There are two main neurotransmitters involved in ADHD: dopamine and norepinephrine. These neurochemicals have been shown to be involved in impulsive control, prioritization, focus, decision-making, frustration tolerance, and time management, among many other important mental processes. The brains of people diagnosed with ADHD show a deficit in these two key neurotransmitters.

Dopamine

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Dopamine (DA) is a neurochemical that is considered to be directly linked with our perception of pleasure and reward. It is what motivates us to seek out what the brain perceives as rewarding to our success and survival. Research has consistently shown that low levels of dopamine appear to be linked to ADHD symptoms.

Those diagnosed with ADHD are thought to be hardwired to seek out high-stimulation activities in order to compensate for low levels of dopamine activity in the reward circuit of the brain. You may find yourself starting tasks with enthusiasm, only to lose interest quickly. Or pursuing different career choices, but burning out halfway through.

Others in the affected person's life, such as friends, family members, coworkers, and teachers, may become frustrated and confused as to why the ADHD-afflicted person can't persist with their goals.

People with ADHD have been observed to have more dopamine transporters in the brain, which cause less dopamine to be available. Scientists believe that the gene related to these dopamine transporters, DAT1, plays a critical role in the condition.

Conversely, this lack of dopamine can make initiating and sustaining your focus through boring or repetitive tasks all but impossible. Boredom can feel almost physically painful. If you're diagnosed with hyperactive or combined type ADHD, this lack of dopamine is part of why you feel a constant sense of inner restlessness, a compulsive urge to seek out new sources of excitement. This can lead to a chronic sense of frustration and dissatisfaction.

If you have ADHD, you may be confused when you notice that sometimes you find yourself intensely focused on a high-stimulus activity, such as playing video games. It's probably difficult to tear yourself away. The brain has found a fountain of dopamine stimulation, so to speak, and it wants to keep interacting with it for as long as possible. This is called hyper-focusing, and while this state has its benefits, it can also have disadvantages when it keeps you from performing less stimulating but more objectively important tasks.

Norepinephrine

Norepinephrine (NE) is another neurochemical that is related to dopamine and is found in lower-than-normal levels in ADHD brains Norepinephrine is involved in focus, processing, and controlling impulsive behaviors. Dopamine is actually a precursor to norepinephrine, but while they play similar roles in the brain, they have somewhat different functions and act on different receptors.

While dopamine and norepinephrine are the main neurotransmitters involved in ADHD, there is evidence that other neurotransmitters may play a role. Scientists suspect that acetylcholine, a neurotransmitter that is abundant in the central nervous system, is important for memory recall and cognitive processing. A lack of acetylcholine and a high level of its associated transporters may play a role in ADHD.

Glutamate signaling may also be involved in ADHD. Further research is needed to fully determine the exact brain functions and neurotransmitter deficits that are involved in the condition.

Brain Areas Affected By ADHD

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People with ADHD have brains that are impacted in a few key regions. Functional MRI (fMRI) has shown abnormal functioning in multiple areas, some showing lower activity than normal and others overactivated. While one study showed a slightly smaller brain size in children with ADHD, intelligence is not impacted by the condition. The difference in brain volume is in areas that are involved with processing and performance. "You know what to do but can't do it," in the words of top ADHD researcher Dr. Russell Barkley.

The prefrontal cortex is the main area affected by ADHD. This area, located in the front of the brain, is responsible for the brain's executive functions, including focus, problem-solving, working memory, impulse control, prioritization, and initiating tasks. Damage to the prefrontal cortex, such as due to a head injury has shown to induce symptoms that resemble ADHD. For people with ADHD, scientists believe that the brain develops differently from the start.

The limbic system is also thought to be involved with ADHD. This is a complex area of the brain made up of multiple regions responsible for processing emotions, memories, and the experience of rewards. This leads to the problems many children with ADHD have with memory and emotional control. Brain scans have shown reductions in volume in this area, as well as both overactivity and under activity that leads to emotional reactivity.

How Medication Improves Symptoms

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Medication used to treat ADHD symptoms falls into two major categories: stimulant and non-stimulant medication. The stimulant medication works by making more dopamine and norepinephrine available in the prefrontal cortex.

Stimulant medication includes the methylphenidates, such as Ritalin, and amphetamines, such as Adderall. These medications have been the subject of many studies testing their efficacy and safety over the last few decades. The majority of people with ADHD who try out stimulant medication will find one that works for them, although it will probably take some trial and error.

Symptoms such as disorganization and procrastination may not be improved with stimulant medication and may require therapy. In addition, some people may experience side effects such as mood changes, irritability, insomnia, and dizziness on stimulants, while others don't respond to the medication at all.

Non-Medication ADHD Treatment

Psychotherapy is a mainstay of treatment for ADHD. Different types of therapy have proven effective for managing ADHD symptoms in children and adults, most notably Cognitive Behavioral Therapy (CBT). In CBT, a therapist can teach you how to alter your negative thoughts and automatic behavioral patterns to better manage the condition. Over time, you can change your behavior to help you function more successfully.

Therapy and medication are often combined and can be an especially effective form of treatment for those with moderate to severe ADHD. While medication can help you focus and be less impulsive, it doesn't teach you actual skills such as prioritization or time management. Behavioral modifications can help you pinpoint trouble areas caused by your ADHD symptoms and put appropriate solutions in place.

Sometimes it can be hard to find a therapist nearby or to fit appointments into your schedule. BetterHelp offers professional counseling that is accessible online from wherever you are. Online therapy allows you to get assistance in managing your ADHD symptoms by removing barriers to treatment and giving you back control.

There is no cure for ADHD, but with proper symptom management and behavioral interventions, you can go on to live a successful and happy life.

Sources:

https://www.additudemag.com/neuroscience-of-adhd-brain/

https://www.gulfbend.org/poc/view_doc.php?type=doc&id=13861&cn=3

https://www.medscape.org/viewarticle/523887

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