The Brain And ADHD: Neurotransmitters That May Cause Symptoms

ADHD is a neurobiological developmental disorder that is reported to affect 9.4% of children and 2.8% of adults in the US, according to a 2016 study. Through extensive research in the last few decades, the medical community has learned much about how the brain is affected by ADHD. 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 puzzle.

ADHD can have 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, maintaining social relationships, or 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 Attention Deficit Hyperactivity Disorder

According to the American Psychiatric Association, attention deficit-hyperactivity disorder (ADHD) is an umbrella term for a condition with three distinct subtypes, often managed with ADHD medications. 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 is thought to develop in the presence of multiple biological and environmental factors. The condition has a significant genetic component, affecting brain anatomy and nerve cells, and it appears to run in families. While ADHD is usually diagnosed in childhood, many adults fly under the radar until they face challenges in adulthood.

ADHD is a developmental disorder of the brain and nervous system, meaning that the structure and function of the brain, such as the frontal lobe and basal ganglia, are different from that of a neurotypical person. ADHD symptoms are thought to be caused by differences in specific neurotransmitter levels, like more norepinephrine, and how certain parts of the brain function, including how neurotransmitters work and how signals travel between nerve cells.

What are neurotransmitters?

Neurotransmitters are chemicals in the brain that transmit signals between neurons or nerve cells. These neurochemicals travel inside areas known as synapses within the various regions of the brain. The entire brain is made up of these neurons in an extensive network, or major networks of brain cells, that controls all our voluntary and involuntary mental and physical processes, including paying attention and managing anxiety.

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, and they work differently. Researchers have found that imbalances in specific neurotransmitters can contribute to conditions such as ADHD, where impulsivity and family problems may exacerbate symptoms. In some cases, ADHD medication is used to address these imbalances, helping individuals to manage their condition better. Understanding where the problem lies in neurotransmitter functioning is crucial for developing effective treatments.

ADHD neurotransmitter types and dopamine transporters

There are two neurotransmitters involved in ADHD: dopamine and norepinephrine. These neurochemicals have been shown to be involved in impulse 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. Scientists continue to study a possible link between serotonin and ADHD, but results remain unclear and little evidence supports this connection thus far. 

Dopamine

Dopamine (DA) is a neurochemical linked with our perception of pleasure and reward. It 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 tend to be hardwired to seek out high-stimulation activities to compensate for low levels of dopamine activity in the reward centers of the brain. You may start tasks enthusiastically, 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, 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 causes less dopamine to be available. Scientists believe 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. For those diagnosed with hyperactive or combined type ADHD, this lack of dopamine caused by the increased number of dopamine transporters is part of why you may feel a sense of inner restlessness or a compulsive urge to seek out new sources of excitement. This is known as reward deficiency syndrome, and it can lead to a chronic sense of frustration and dissatisfaction, and in some cases may lead to substance abuse. 

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 found in lower-than-normal levels in ADHD brains. Norepinephrine is involved in focus, processing, and controlling impulsive behaviors. Dopamine is 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 primary 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 involved in the condition.

Brain areas affected by ADHD

ADHD impacts a few key regions of the brain. Functional MRI (fMRI) has shown abnormal functioning in multiple brain regions, 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. Having ADHD does not necessarily mean having a learning disability. The difference in brain volume is in areas 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 to show significant differences with ADHD. This area, located in the front of the frontal cortex in the forehead area 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 a head injury, has been shown to induce symptoms that resemble ADHD. For people with ADHD, scientists believe that the brain development is different 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 underactivity that lead to emotional reactivity.

How medication improves ADHD symptoms

Medications used to treat ADHD symptoms fall 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 methylphenidate, 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. Most people with ADHD who try 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 treatment for the ADHD brain

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 negative thoughts and automatic behavioral patterns to manage the condition better. Over time, you can change your behavior to help you function more successfully.

In addition, therapy can be beneficial for treating co-occurring mood disorders. Anxiety disorders and major depressive disorder are commonly experienced by ADHD patients, and even those who are not diagnosed with a mood disorder can have frequent mood swings. Therapy can offer healthy coping mechanisms to manage symptoms. 

Therapy and medication are often combined and can be an especially effective form of treatment for those with moderate to severe ADHD or if ADHD is present with another condition, like obsessive-compulsive disorder or a mood disorder. While medication can help you focus and improve impulse control, it doesn't teach you 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 mental health professional nearby or to fit appointments into your schedule. BetterHelp offers professional counseling that is 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. It’s also been shown to be just as effective as in-person therapy.