Genetics of ADHD
Imagine your body as a vast collection of tiny communities or towns. Each cell is a town, and the towns contain roads and factories, and even a town library. In each library (the cell nucleus) there are instruction manuals that are necessary to help the town function. These instructions manuals are your DNA, the genetic code used to create you from a tiny embryo to an adult human. Each person receives half of their generic code from their mother and half from their father— passed down from one generation to the next. This is why you may look like your grandmother or great, great uncle. Genetic traits (genes) that create hair color or eye color are not the only traits passed down: genes may also carry traits that predispose you to conditions like ADHD.
If you have ADHD, it's more likely someone else in your family has it too. Alex's tale of a forgetful grandfather and an aunt who perpetually lost her keys isn't just coincidence; it's genetics in action. ADHD is notably influenced by our genes. Around 75% of the variation in ADHD occurrence in the population can be attributed to genetics. So, if you picture 10 individuals with ADHD, for about 7 of them, their ADHD has been largely shaped by their genetic code.
Now, to get a clearer image of this genetic link, let's consider twins. If one identical twin, like our dynamic teacher Jordan, has ADHD, there's a very high likelihood the other will too. If Jordan had an identical twin, Jamie, and Jordan has ADHD, there's an 8 in 10 chance that Jamie would also have ADHD.
Yet, while our genes play a huge part, it's not as straightforward as one might think. There's no single "ADHD gene" but rather multiple genes that, in small ways, contribute to the condition. Imagine assembling a puzzle. No single piece completes the image: each piece contributes a section to the overall scene. A person with ADHD might have inherited a mix of these genetic “puzzle pieces” from their parents, making them slightly more predisposed to ADHD.
For example, genes related to the function of certain neurotransmitters in the brain, such as dopamine, have been frequently implicated in ADHD. For instance, let's think about Alex's case. Genetic testing revealed a variant in their DRD4 gene, one of the dopamine receptor genes that have been linked with ADHD. This genetic variant doesn't definitively mean that Alex would have ADHD, but it contributes to their overall risk.
Even though there is no single “ADHD gene”, we know that someone with ADHD who has many ADHD-causing genes, has similar genes to someone who has fewer ADHD-causing genes. This means that all types of ADHD, whether you have “more” or “less” ADHD symptoms, are connected by the same collection of genes. This helps scientists understand that all ADHD is one similar condition, no matter how much or little you feel the ADHD symptoms.
It's important to remember that genetics is not destiny. Just because you have a genetic predisposition doesn't mean you will develop ADHD. Environmental factors, prenatal health, and many other aspects also come into play. Taylor, our astute law student, might carry a genetic predisposition for ADHD, but elements in her surroundings, such as exposures during her mother’s pregnancy or early childhood experiences, could influence how these genes act out.
Think of two people who both have the collection of genes that could lead to ADHD. The one who grows up with less attention and support from their parents is more likely to end up showing ADHD symptoms than someone who's grown up in a more attentive and nurturing environment. It's a bit like saying our genes lay down the groundwork for ADHD, but it's the environment that strongly influences what actually happens in real life. So, even if you have the genes for ADHD, a positive and supportive environment can make a big difference, sometimes reducing the chances of those symptoms showing up.
Also, while genetic testing might provide some information, it's not currently used for diagnosing ADHD. The diagnosis is based on observed behavior and history, and while genetics plays a significant role, understanding and managing ADHD involves considering the whole person and their environment.
If you think of an ADHD personality as a tapestry, the genes can be represented by the threads, while the environment and life experiences create the overall patterns of the tapestry. Alex, Jordan, and Taylor, all navigate the challenges of ADHD, each with a unique genetic code, interwoven with their family genetic histories and personal life experiences. Understanding this offers a deeper appreciation of ADHD's complexity and its presence across generations.
How Our Evironment Shapes Ones Risk for ADHD
Let’s look at how environmental factors can contribute to ADHD. While genetics play a big role in the condition, environment can also have a significant impact.
To start, prenatal exposure to substances like alcohol, tobacco, or drugs can increase the risk of ADHD. For example, if Taylor's mother had smoked during pregnancy, research shows that it could have increased Taylor's risk of developing ADHD by about two and half times. It's estimated that about 1 in 3 people exposed to tobacco smoke prenatally might develop ADHD. Substance use during pregnancy can also increase the risk. If a mother consumes alcohol or uses illicit drugs during pregnancy, these substances can affect the developing fetus and increase the risk of ADHD.
Another significant environmental factor is exposure to lead, often found in lead paint and lead pipes in older homes. If Taylor grew up in an older house with lead paint, this exposure could have contributed to their ADHD. Elevated blood lead levels, even those previously considered safe, are associated with an increased risk of ADHD. For instance, children with blood lead levels of 2 micrograms per deciliter or higher were reported to have a four times higher likelihood of having ADHD compared to those with levels below this.
Early childhood trauma or high levels of stress can also increase the risk of ADHD. Suppose Jordan grew up in an environment with a high level of stress or even experienced traumatic events. In that case, these experiences might have contributed to their development of ADHD. In a large study, those who experienced four or more adverse childhood events were three times more likely to use ADHD medication.
Even conditions after birth can influence the development of ADHD. For example, Alex was diagnosed with ADHD and also had a history of early and recurrent ear infections. This isn't a random coincidence. Some studies suggest that children who have multiple early infections requiring antibiotic treatment might have a slightly increased risk of developing ADHD.
Just like with genetics, it's essential to remember that environmental factors alone do not determine if someone will develop ADHD. It's typically a combination of genetic, environmental, and neurological factors that come together to create this condition.
Imaging ADHD Brains: What do ADHD brains look like?
Imagine your brain is like a big, busy city with lots of buildings, roads, neighborhoods and parks. Now, scientists have these special cameras, called neuroimaging instruments, which can take pictures of this “city” without opening up the brain. These pictures help scientists see how your brain is built and how everything works together. They can actually see the different interactions in the different “neighborhoods.”
For some people, their brain-city is set up in a way that makes it harder for them to sit still or pay attention. What is now called ADHD.
When scientists look at the pictures of people with ADHD, they sometimes see that some buildings (or parts of the brain) might be a little smaller or bigger, or the roads (connections) might be different. It's like having a city with more roundabouts than straight roads, making the traffic flow a bit differently.
And just like how every city is unique and special, like New York with its big skyscrapers or Venice with its web of canals, every person's brain is unique too. Neuroimaging just helps scientists understand how each brain is special in its own way.
Let’s continue our journey through the fascinating cityscape of the brain.
In one corner of our brain-city, there's a bustling downtown area called the Prefrontal Cortex. This is where all the planning, decision-making, and self-control happens. Imagine it as the mayor's office of the city. For a boy named Lucas, who has ADHD, this office might look a little different. Whereas in most cities the mayor's office has many planners and organizers to make sure everything runs smoothly, Lucas's office might be a bit understaffed, making it harder to keep tra of tasks or plan ahead. That's why sometimes Lucas might blurt out answers in class without waiting his turn or forget to do his homework.
Then, there's a special building, the Basal Ganglia, which you can think of as the city's reward center. It's like a big amusement park where people go to have fun and feel good. For Mia, another child with ADHD, her amusement park gives out fewer tiets than usual. Because of this, Mia is always on the lookout for exciting things, trying to get as many tiets as she can. This might explain why she often jumps from one activity to another, seeking that thrill.
Now, every city has roads and highways that connect different neighborhoods, ensuring smooth traffic. These connections in the brain help different areas talk to each other. In Jamie's brain, some of these roads have a few more speed bumps and detours, making the flow of cars (or information) a bit slower. This could be why Jamie sometimes finds it challenging to switch between tasks or struggles with multi-step instructions in school.
Lastly, there's a grand theater in our city, the Amygdala, where all emotions are played out. In Zoe's brain-city, her theater has a super-sensitive sound system. Every emotion feels louder and more intense. This can make Zoe's reactions stronger than her classmates, like being extra upset over a lost pencil or super excited about a weekend trip.
But here's the thing: just as each city has its unique charm, so does each brain. Lucas's, Mia's, Jamie's, and Zoe's brain-cities, with their quirks and differences, make them see the world in their special way. And with the right support, like traffic signals and road signs, their brain-citys can function as efficiently as anyone else. Scientists use these special cameras, the neuroimaging tools, to better understand these brain-cities, ensuring every child gets the best help to navigate their unique situation.
How Our Brains Communicate
We’ve talked about how the structure of the brain can vary from person to person, but there are other ways the ADHD brain can be different. Our brains continuously use hard to see chemicals, which we’ll call the “communications system”, that let different neighborhoods of the brain talk with each other.
Meet Max and Olivia. Both are students, and while they come from similar bagrounds, the way they interact with the world is quite different due to the unique nature of their brains' "communication systems."
Max has ADHD. In his brain, there's a lively dance of chemicals called neurotransmitters, which are like special messengers. Dopamine, the "reward messenger", which doesn’t last long enough for Max to complete a task. Because of this, tasks that others find rewarding, like finishing homework, don't give Max the same satisfaction.
Similarly, another messenger, norepinephrine, which helps with attention and alertness, often doesn't show up in the right amounts. Imagine trying to listen to your favorite song, but the volume keeps fluctuating, making it hard to enjoy or even follow along. For Max, this means his mind is likely to wander when others are paying attention.
Now, Olivia, who doesn't have ADHD, experiences a different dance. Her dopamine stis around just the right amount of time, giving her a sense of achievement when she completes tasks. Norepinephrine, on the other hand, plays at just the right volume, allowing her to concentrate on tasks, like reading a book, without easily getting distracted by baground noise.
Both Max and Olivia are bright and capable. But the unique dance of neurotransmitters in their brains shapes their experiences and behavior. The good news for Max is that there are scientifically proven methods to help him—to adjust the way his brain functions.
One day, Max met Dr. Patel, a kind and understanding doctor who explained that the unique dance of neurotransmitters in his brain could be adjusted to help him focus and feel rewarded, much like Olivia does naturally. Dr. Patel described medications for ADHD as special tools that help "tune" the rhythm of the dance, making sure all messengers dance in harmony.
For example, Dr. Patel introduced Max to a medication called a stimulant. While the name sounds like it would hype Max up, it actually does the opposite. This medication helps increase the amount of dopamine and norepinephrine in the brain, making the dance more coordinated. With the medication, the "reward messenger" dopamine stays around longer, helping Max feel the satisfaction of completing tasks. The "attention messenger" norepinephrine also becomes more consistent, so it's like turning the volume of Max's favorite song to just the right level, allowing him to concentrate better.
After some time on the medication, Max noticed that tasks, like studying for a test or finishing a project, became more manageable. He felt more in tune with his surroundings, similar to how Olivia did. One day, he proudly showed Dr. Patel a project he'd finished, mentioning how he'd felt a genuine sense of accomplishment and didn't get distracted even when his little brother was playing loudly in the next room.
However, Dr. Patel emphasized that everyone's dance is unique. While some people, like Max, may benefit from stimulant medications, others might find non-stimulant medications more effective. These non-stimulants work a bit differently but also aim to balance out the dance of neurotransmitters.
For instance, there's Sarah, another of Dr. Patel's patients. Stimulants caused her to feel jittery. Dr. Patel then recommended a non-stimulant medication, which worked to fine-tune the norepinephrine in her brain. With this, Sarah's concentration improved, and she felt calmer and more in control.
Both Max and Sarah's stories show that with the right support and treatment, the dance of neurotransmitters in those with ADHD can be adjusted, helping them navigate their world with more ease and confidence.
