What Are the Main Causes of ADHD?
No one knows exactly what causes ADHD . But experts think it's rooted in a mix of factors.
"Like most mental health conditions, there is some sort of biological nature," says Lauren Haack, PhD, associate professor of psychiatry and attending psychologist at the University of California San Francisco (UCSF) Weill Institute for Neuroscience in San Francisco, CA.
"It does run in families. Something about a person's genes influence how their brain and nervous system developed. And then there also is an interaction with the environment."
While any of these factors alone won't give you or your child ADHD, they can affect how severe your symptoms are, and your ability to manage them.
ADHD causes vs. effects
There's no way to find the reason why one person has ADHD and another doesn't. It can be hard to tell the difference between some ADHD causes and effects. This condition may happen with other conditions. For example, it may come with other issues related to:
- Behavior
- Conduct
- Learning
- Anxiety
- Depression
You or your child may have other conditions such as:
- Oppositional defiant disorder (ODD)
- Conduct disorder
- Learning disorders, including dyslexia, dyscalculia, or dysgraphia
- Anxiety disorders, including separation anxiety, social anxiety, or general anxiety disorder (GAD)
ADHD also has been linked to allergies. But it isn't clear if one causes the other. ADHD also is tied to addictive behavior, such as internet gaming disorder (IGD).
Connections between ADHD and other conditions go both ways. ADHD may raise your risk for these other conditions. When you have ADHD, you may turn to video games or other options as a way of getting through. But that doesn't mean playing video games can cause ADHD or that allowing your child to play video games is the reason why they have ADHD.
Is ADHD Genetic?
It can be. ADHD tends to run in families. Studies suggest children of ADHD parents are 40% more likely to also have it.
Some studies in twins suggest nearly 75% of ADHD may be explained by genetics and the other 25% by environment or interactions between your genes and your environment. But ADHD isn't passed down in a simple way. It involves many genes, each likely to have relatively small effects. Many of those genes play a role in early brain development. One study showed genes linked to ADHD are especially important in the brain in late infancy. It also pointed to a role for genes involved in your immune system.
Some other studies suggest differences in the genetics of ADHD depending on your ancestry. But more study of ADHD in people from different parts of the world is needed to better understand genes involved in ADHD and how they affect your biology, brain, and ADHD risk.
Early Environmental Risk Factors for ADHD
Your early environment is especially important when your brain is still developing. For instance, studies show your mother's environment when she was pregnant with you would play an important role in your ADHD risk, in addition to genetics. That includes your mother's exposure to toxins, substance use, and malnutrition.
The frontal lobe is the part of your brain that allows for focused attention. It's involved when you shift your attention. It's important for goal-oriented activities and impulse control.
"Anytime you have exposure to a toxin in utero, it's going to affect those higher order functions first," Haack says. "Something like malnutrition in utero or parental substance use are pretty well documented to have an influence on increasing your likelihood of presenting with ADHD."
Other factors early in life may play a role in your risk for ADHD, too. For example, studies suggest a mother's vitamin D deficiency may raise her child's risk for many mental health conditions, including ADHD. Other studies suggest your risk for ADHD may also be linked to your mother having had high stress and high levels of testosterone when she was pregnant with you. But these findings aren't consistent, and more study is needed.
Other Risk Factors for ADHD
Infants born premature or with a low birth weight or whose mothers had difficult pregnancies, go on to have a higher risk for ADHD. The same is true for children with head injuries to their brain's frontal lobe, the area that controls impulses and emotions.
Studies also show that pregnant women who smoke or drink alcohol may have a higher risk of having a child with ADHD. Exposure to lead, PCBs, or pesticides may also have a role.
Researchers believe some toxins may interfere with brain development, which may lead to hyperactivity, impulsive behavior, and trouble paying attention. But there's no way to find a specific reason why you or your child has ADHD.
Your ADHD symptoms may seem better or worse at different times, depending on environmental and other factors.
What Doesn't Cause ADHD
Although it's been debated, research doesn't show ADHD is caused by eating too much sugar, drinking caffeine, or watching a lot of TV.
Some other factors studied for links to ADHD are:
Parenting styles. Your parenting won't cause ADHD. But there are methods you can use to help support your child with ADHD.
"The way a child receives instructions from parents and teachers — how clear and consistent those instructions are — and then how we respond to a child's behavior can influence and exacerbate or help those symptoms or features of ADHD," Haack says. "Parenting doesn't cause ADHD, but it can influence the way it presents."
Diet. A healthy diet is good for your brain, but no particular food or dietary pattern has been shown to cause ADHD. But malnutrition or certain nutritional deficiencies in utero or very early in life may come with more ADHD risk.
Playing video games. There's no evidence playing video games causes or worsens ADHD. At the same time, some kids with ADHD may be drawn to fast-paced games on the screen.
Children with ADHD may "hyper focus" while playing video games, which can lead to spending too much time playing them. So, while the games themselves don't cause ADHD, they're something parents may want to limit, especially in children with ADHD.
Distracting environments. If you have ADHD, distractions may make it harder to function. But distractions aren't the cause of ADHD.
"We don't have evidence that being in a distracting environment, such as having more screens open or more notifications, causes ADHD," Haack says. "But we do have evidence that you can make your symptoms or impairment from ADHD worse, and there are ways to tweak the environment and the way everything is set up so that you can function better, whether you're a child, teen, or adult with ADHD."
Poverty. ADHD is more likely when you have lower income. Socioeconomic status affects a wide range of factors that may influence ADHD in complicated ways. So, by itself, poverty doesn't cause ADHD. But it may make many other things that affect ADHD more likely, including stress and malnutrition.
Stress and trauma. Stress and trauma don't directly cause ADHD, but they affect it in complicated ways. If you have childhood trauma and other stressful life events, you're more likely to have ADHD that's serious and lasts into adulthood. ADHD also can lead to more stress, whether it's in school, work, or relationships.
Studies suggest complicated connections between ADHD, anxiety, stress, and inflammation. More study is needed to understand how stressors in life affect brain development and the risk for ADHD.
What Goes On in the ADHD Brain
ADHD brains work differently. Studies show brain chemicals, called neurotransmitters, don't work the same when you have ADHD. There also tend to be differences in the way your neural pathways work.
Certain parts of your brain may be less active or smaller when you have ADHD. The brain chemical dopamine may also play a role. It carries signals between nerves in your brain. It's linked to movement, sleep, mood, attention, and learning.
Your frontal lobe is the biggest brain area affected in ADHD. It's important for:
- Planning
- Organization
- Focus
- Attention
- Self-control
- Self-monitoring
- Memory
- Communication
- Problem-solving
- Impulse control
- Language
- Social behavior
- Motivation
- Judgment
When you have ADHD, different parts of your brain also may work together differently. In addition to executive functioning, ADHD also may involve changes in reward pathways in your brain.
"If you look at brain studies of people with ADHD, their brains actually get more lit up by immediate, tangible rewards," Haack says.
"Someone without ADHD may get that same sort of motivation and benefit from a farther off, more intangible reward. And, so, I think that that really can help explain why people with ADHD may have a harder time completing tasks that don't have this sort of immediate, tangible benefit."
Can ADHD Be Prevented?
Maybe sometimes. But ADHD is strongly influenced by your genetics. Avoiding environmental factors linked to ADHD may help you avoid ADHD or lower your risk. But there's no guaranteed way to keep you from getting it. It's possible that early diagnosis and care could help make ADHD symptoms less serious and limit long-term complications.
When to Talk to a Doctor About ADHD
If you're worried you or your child may have ADHD or your risk for it is high, talk to your doctor. Consider seeing one who specializes in ADHD.
It's common for young kids to have some behaviors and signs that might look like ADHD. Because of this, those who have ADHD may not get diagnosed until they start school. You can be diagnosed with ADHD at any age.
Takeaways
ADHD is a complex condition, where genetic and environmental factors can raise your risk. Exposures early in your development are important, but you can be diagnosed with it at any age. Treatments and other care measures can help manage ADHD symptoms. If you think you or your child has ADHD, talk to your doctor.
FAQs About the Causes of ADHD
Is ADHD caused by bad parenting or lack of discipline?
No. Parenting styles don't cause ADHD. In fact, certain parenting ways may help your child with ADHD.
Can diet or sugar intake cause ADHD in children?
No. You may find it helps to eat healthy and limit sugar, but diet doesn't cause ADHD.
Does screen time contribute to the development of ADHD?
While excessive screen time doesn't cause ADHD, it's linked to increased ADHD-related behaviors and symptoms.
Can ADHD develop later in life, or does it only start in childhood?
You can develop ADHD at any age.
