Researchers don’t know exactly what causes ADHD in children, but they do know the risk factors. Here’s some intel that might clarify.

Finding out that your child has attention deficit hyperactivity disorder (ADHD) may bring up a whole bunch of feelings.

And chances are, as soon as you heard the news, thoughts, questions, and “what ifs” started to swirl in your head: “Did I do something wrong? How did this happen? Are they going to be OK?

Let’s start at the beginning.

Technically, we’re not totally sure any child is born with ADHD. So far, we just know that genetics play an important role, thanks to studies of twins and families.

Roughly 3 in 4 children with ADHD have a relative with the condition. In fact, some studies have found this hereditability to be 70 to 80%.

“Kids are born with the underlying mechanisms that cause ADHD,” explains psychologist Jessica Myszak, “but babies and young children would never be diagnosed with ADHD.”

In other words: A baby might be born predisposed to have ADHD, but that doesn’t mean they’ll develop it.

A note on genetic predispositions

Your genes play a role in whether you will develop some mental or physical health conditions, but they’re only one piece of the puzzle.

Epigenetics is the study of how the DNA you inherit does or does not manifest in you. This means that any genetic predispositions that run in your family can stay inactive or can even be reversible when signs show up early.

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ADHD has been diagnosed in children and teens who have no family history of the condition, which suggests there’s more than one cause.

Some other causes include:

Exposure to environmental toxins

Research suggests that exposure to certain toxins, either in utero or at a young age, might lead to ADHD.

One of those toxins could be lead, which is found in a variety of places, including in the paint of homes built before 1978 and in gasoline. The heavy metal seems to be associated with inattention, hyperactivity, and impulsivity — all symptoms of ADHD.

Another toxin that could be linked to ADHD is a pesticide called organophosphate. It’s commonly sprayed on lawns and agricultural products.

Research has shown that it affects kids’ neurodevelopment, so some scientists think it could also be linked to ADHD.

Health during pregnancy

Several studies have found that if a fetus is exposed to tobacco and or alcohol, it can increase the risk that the baby will develop ADHD.

For example, a 2018 study found that children were at greater risk of having ADHD if their birthing parent was a heavy smoker.

Another 2018 study made a connection that pregnant people who drank at least four alcoholic drinks in one sitting during pregnancy were more likely to have a child who had ADHD.

Poor nutrition and infections during pregnancy can raise the risk of the child having ADHD too.

“Known risk factors for ADHD include maternal diet during pregnancy,” Myszak says. “This also includes particular medications, such as antidepressants, antihypertensives, and caffeine.”

Being born early or having a low birth weight also appear to be risk factors.

Traumatic brain injury

Some ADHD diagnoses seem to be the result of brain damage, such as from:

  • a brain injury early in life
  • trauma
  • abnormal brain development


Some studies have also found that meningitis or encephalitis might also result in ADHD in kids.

“There is no single test to diagnose ADHD,” explains Dr. Dilip Karnik, a pediatric neurologist who specializes in ADHD and autism. “Some of the signs can also look like other disorders.”

That’s why ADHD diagnosis often involves evaluations by pediatricians and psychologists over a period of time, as well as parent checklists, in-office assessments, and teacher interviews.

The earlier it’s diagnosed, the better. That’s why, Karnik says, he “always encourages parents to trust their instincts.”

He continues, “Many parents often have a ‘gut feeling’ that their child is having difficulty, that something is not right, and if that’s the case, they should ask questions.”

Common signs of ADHD in children

  • daydreaming
  • having trouble focusing on tasks they’re not interested in
  • difficulty resisting temptation
  • talking too much
  • restlessness
  • hyperactivity
  • acting without thinking
  • disruptive outbursts
  • easily distracted
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Teachers often play a valuable role in noticing these common signs.

In preschool

Preschool is still a little too young to diagnose ADHD in most cases, unless the ADHD is severe.

“In general, children suspected of ADHD at this age are extremely impulsive and hyperactive,” Karnik says. “Much more than you would expect at 3 years old, and it’s not just an immaturity issue.”

Instead, doctors don’t usually diagnose ADHD in children until they’re at least 5 years old.

In elementary school

Elementary school is when most diagnoses happen.

“ADHD is easier to identify in a structured environment,” Karnik explains. So, teachers are more likely to notice the child who is constantly daydreaming, super talkative in class, or easily distracted during activities like circle time.

During parent-teacher conferences, you might hear that your kid has often been impulsive, demanding, or unable to complete projects.

However, says Myszak, your child shouldn’t just be having trouble at school. You should be seeing these same symptoms at home or in extracurricular activities too.

“If there is only one place that is problematic, it might be an issue with that particular environment rather than ADHD,” she says.

In middle and high school

“Sometimes kids are not identified [with ADHD] until much later,” Myszak says. “In these cases, there is evidence that the child had difficulty with attention, but either they were able to compensate for these difficulties when the material was easier, or due to cultural factors, their symptoms are not recognized.”

However, later in school, ADHD can have a bigger impact on schooling. Kids with undiagnosed and untreated ADHD can do poorly in school or get involved in high-consequence behavior, such as substance use.

There’s not much you can do to prevent ADHD — at least not yet.

The best thing you can do, says Myszak, is manage your wellness and take care with the environment you’re exposed to during pregnancy, as much as is feasible.

Myszak encourages parents to “receive prenatal healthcare and avoid exposure to drugs, alcohol, tobacco.”

The more you know about and understand your child’s diagnosis, the better you can help them cope.

That’s why Myszak recommends parents read books about ADHD, such as:

Other educational and supportive resources include:

  • HelpGuide, an independent nonprofit focused on mental health
  • ADDitude, a website and magazine dedicated to ADHD
  • CHADD, the largest national support organization for ADHD that features a resource directory to find professional help
  • ADDA, an association that provides info and training resources, and promotes ADHD awareness

You can also look into Parent-Child Interaction Therapy, which Myszak recommends to families who are struggling to manage their child’s behavior at home.

“It’s a parent-coaching model of therapy that helps parents learn to support their child and consistently and effectively manage their behavior,” she says.