Reviewed by Laura Angers, LPC
The brain is the most complex organ in the body. Even though we’ve spent several hundred years studying the brain and everything it’s responsible for, there’s still so much left to uncover -- especially when it comes to ADHD symptoms.
Thus far, researchers are unsure of what causes ADHD symptoms -- such as inattentiveness, hyperactivity, and impulsiveness. Some researchers believe the symptoms are caused by genetics, some believe the environment causes it, and others believe an injury to the brain is responsible.
While there are several risk factors to ADHD, none have caught the attention of researchers worldwide more than the anatomy and structure of the brain. More specifically, they’re studying neurotransmitter activity -- such as dopamine -- in certain areas throughout the brain.
So, what is dopamine?
In the early 1900s, scientists started to synthesize dopamine for the first time. It wasn’t until the mid-1950s that scientists started discovering the role dopamine and ADHD plays in the body. At first, it was believed to be a precursor to two neurotransmitters, epinephrine and norepinephrine.
Over time, scientists learned that dopamine is more than just a precursor to epinephrine and norepinephrine. Instead, it acted as a neurotransmitter itself and played an enormous role in our ability to seek and achieve pleasure in life situations. In fact, these neurotransmitters also act as hormones in the body (in addition to neurotransmitters in the brain).
Dopamine is produced in the substantia nigra and the ventral tegmental areas of the brain. It all starts with an amino acid called L-Tyrosine, which is found in meat, fish, eggs, dairy products, beans, nuts, oats, and wheat. The body converts L-Tyrosine into L-DOPA, another amino acid, before converting it into dopamine.
Once produced, dopamine is released by the hypothalamus, located on the brain's base or undersurface. The dopamine travels through the millions of neurons that make up the brain and is passed from one neuron to the next through the synapse (the tiny space between neurons).
When dopamine crosses the synapse, it binds to a dopamine receptor on the end of the other neuron. Binding to a dopamine receptor is what triggers a response or action in the brain. With dopamine, the response is characterized by the feeling of pleasure.
Since dopamine is a precursor to epinephrine and norepinephrine, the individual might also experience a change in heart rate and blood pressure, known as the fight or flight response.
WHAT REGIONS OF THE BRAIN ARE INVOLVED?
It’s clear that dopamine, epinephrine, and norepinephrine are the three main neurotransmitters involved in ADHD, but it’s not just the neurotransmitters that are important here. You also have to look at the brain's different areas to understand how these neurotransmitters affect ADHD symptoms.
Scientists believe four main brain areas are involved with ADHD -- the frontal cortex, limbic system, Basal ganglia, and Reticular activating system. Let’s take a closer look at each area:
- Limbic System -located on both sides of the thalamus deep inside the brain, the limbic system includes the hypothalamus, amygdala, and hippocampus. This region of the brain is responsible for emotions, motivation, learning, and memory.
- Basal Ganglia -another group of structures located deep inside the brain, the basal ganglia includes the caudate, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. It’s responsible for motor control, motor learning, executive functions, emotions, and behaviors.
- Frontal Cortex is the front area of the brainresponsible for high-level functions in the body and brain. For example, it plays a role in executive functions, motor function, problem-solving, impulse and spontaneity, judgement, language, and behavior.
- Reticular Activating System -a group of nuclei connected inside the brain that regulates the sleep-wake cycle. It also plays a major role in filtering out the unnecessary information our brains come in contact with. To put it simply, your reticular activating system allows you to filter through the things you’re focused on at that moment in time.
Scientists believe that a lack of dopamine, epinephrine, or norepinephrine in these areas of the brain is partly responsible for the symptoms experienced with ADHD patients.
It should also be noted that these four regions of the brain work together. An issue in one region likely means an issue with another one, creating a domino effect. As we learn more about the role neurotransmitters play in each region, researchers will start to find more accurate treatments when relieving the symptoms of ADHD.
DOPAMINE’S EFFECT ON ADHD SYMPTOMS
Like we mentioned above, scientists and researchers continue to uncover more about dopamine and its effect on ADHD symptoms. It was once believed that low levels of dopamine, epinephrine, and norepinephrine were the underlying cause of ADHD, but that no longer seems to be the case.
Instead, scientists have shifted their focus to high concentrations of dopamine transporters in the brain. These transporters are responsible for transporting dopamine back into the nerve cell via the presynaptic membrane, where the dopamine is released.
Issues begin to arise when there are too many dopamine transporters at work inside the brain. Since they remove dopamine from the synapse and back into the nerve cell, the transporters don’t give dopamine enough time to unleash its effects. Low levels of dopamine are not the cause of the issue, but rather how the brain utilizes the produced dopamine.
Without the effects of dopamine, the individual finds it difficult to seek pleasure and feel rewarded throughout the day. These individuals are chemically wired to seek more in life due to their inability to feel comfortable in any situation. As you can imagine, this leads to inattentiveness, impulsiveness, and hyperactivity -- the three major symptoms of ADHD.
WHAT ABOUT SEROTONIN?
Serotonin is another major neurotransmitter that researchers believe plays a role in ADHD symptoms. While not as popular as dopamine, epinephrine, and norepinephrine in ADHD, serotonin receives most of its attention when dealing with depression.
Where dopamine is responsible for pleasure and reward, serotonin is responsible for happiness and overall well-being. It’s mostly known for its effect on our daily mood and behavior, but it also plays a role in sleeping, eating, and digestion.
Many of us have heard of this neurotransmitter because it’s converted in the body from tryptophan, one of the more well-known amino acids. Tryptophan is one of the essential amino acids, meaning the body can’t produce it on its own, and we must receive enough each day through our diet. It’s mostly found in turkey, eggs, cheese, pineapples, nuts, seeds, and salmon.
Low levels of serotonin or high concentrations of serotonin transporters could result in an uneasy, unhappy feeling throughout the day. While this isn’t experienced in all ADHD patients, it’s seen enough for it to be a cause for concern.
OTHER RISK FACTORS WITH ADHD
The connection between dopamine and ADHD is pretty clear. While brain structure, brain anatomy, neurotransmitter activity, and brain function are some of the most studied causes of ADHD in children and young adults, they don’t tell us why our brains experience these complications or where they root from.
With that being said, researchers are looking at a wide variety of potential causes for ADHD and what might cause the brain to suffer from these complications. So far, researchers are interested in environmental causes, genetics, and brain injuries.
Environmental causes include how the child is raised, premature births, smoking or drinking during pregnancy, excessive amounts of lead in the body, a lack of exercise, and a lack of structure or daily routine. Scientists believe any of the above could cause symptoms related to ADHD.
In addition to that, genetics and heredity are also causes for concern. In fact, 25% of all ADHD patients have at least one parent that also suffers from the disease. ADHD is also known to be diagnosed with siblings, as well. Of course, brain injuries also need to be considered here, which could have an enormous impact on brain function.
When diagnosing ADHD in a child, the doctor performs a psychiatric and physical evaluation and looks at the patient’s family history and family behavior.
ARE YOU SUFFERING FROM ADHD?
ADHD, also known as attention-deficit/hyperactivity disorder, is a serious mental illness that affects nearly 6.1% of all children. The average age of diagnosis is seven years old, but the symptoms are often experienced as early as 3-6.
What’s troubling about the future of ADHD is that we’ve seen an increase of over 42% in ADHD diagnoses over the past eight years -- an astounding number that will likely continue to increase until more accurate and effective treatments are discovered.
There are three main symptoms with ADHD -- inattentiveness (difficulty staying focused), impulsiveness (not thinking before acting), and hyperactivity (not being able to sit still). With the lack of dopamine, epinephrine, norepinephrine, and serotonin, ADHD individuals often have difficulty achieving fulfillment in life.
Not only that, but ADHD often leads to outside behaviors that affect someone’s life. For example, those suffering from ADHD often struggle in the classroom or at work, are prone to injuries and accidents, lack self-esteem, struggle to make friends, and turn to drugs or alcohol often. As you can imagine, these behaviors only make the disease worse.
Knowing when to seek help is very important when suffering from ADHD. Since it’s mostly found in children, it’s often the parent’s responsibility to detect the illness and help the child seek the proper help so they can live a normal and happy life.
If you fear your child is struggling with ADHD, or if you feel you’re struggling with it yourself, speaking with a doctor is often the first step in receiving help. If you’re unsure if it’s ADHD or something else, we have an online test that’ll help.
At Mind Diagnostics, we created an online ADHD test to help others detect this horrible mental illness. We understand that the sooner you receive help, the sooner you can start to gain control of your life again. Our test only takes a few minutes, but it could save you from a world of stress, frustration, and uneasiness.