What Is ADHD?

Published April 7, 2020

Now, more than ever, parents who suspect their child might have ADHD – and parents of children diagnosed with this condition – need to evaluate information, products, and practitioners carefully.


This NICHCY Briefing Paper is intended to serve as a guide to help parents and educators know what ADHD/ADD is, what to look for, and what to do.

While acknowledging that adults, too, can have ADHD, this paper focuses on the disorder as it relates to children and youth.


What is ADHD?

ADHD, or Attention Deficit Hyperactivity Disorder is a condition that causes a variety of symptoms, and is generally known for causing inattentiveness, impulsivity, and/or hyperactivity.

The symptoms differ from person to person. ADHD was formerly called ADD, or attention deficit disorder. Both children and adults can have ADHD, but the symptoms always begin in childhood.

Adults with ADHD may have trouble managing time, being organized, setting goals, and holding down a job. They may also have problems with relationships, self-esteem, and addiction.

ADHD is the most commonly diagnosed mental disorder of children. Children with ADHD may be hyperactive and unable to control their impulses. Or they may have trouble paying attention. These behaviors interfere with school and home life.

ADHD more common in boys than in girls. It’s usually discovered during the early school years, when a child begins to have problems paying attention.

How common is ADHD?

  • Many reports estimate that anywhere from 5% to 8% of school-age kids have the disorder.
  • The Center for Disease Control (CDC) reports that prevalence is closer to 11%.

Some doctors might give children an ADHD label even when they may have another educational, behavioral, or mental issue. The flip side is that some kids who truly have the disorder aren’t getting diagnosed with it.

ADHD often overlaps with a lot of other problems, and many clinicians don’t know how to categorize what they’re seeing.

What experts do know for sure: ADHD is one of the most common behavioral disorders that happens in childhood, according to both the CDC and the National Institutes of Health.

What causes ADHD ?

No one knows exactly what causes ADD/ADHD.

Scientific evidence suggests that the disorder is genetically transmitted in many cases and results from a chemical imbalance or deficiency in certain neurotransmitters, which are chemicals that help the brain regulate behavior.

No one knows exactly what causes ADD/ADHD, but certain things are known to play a role.

The Family Connection: ADHD runs in families. Anywhere from one-third to one-half of parents with ADHD will have a child with this condition as there are genetic characteristics that seem to be passed down.

  • If a parent has ADHD, a child has more than a 50% chance of having ADHD.
  • If an older sibling has it, a child has more than a 30% chance.

Pregnancy Problems: Children born with a low birth weight, born premature, or whose mothers had difficult pregnancies have a higher risk of having ADHD. The same is true for children with head injuries to the frontal lobe of the brain, the area that controls impulses and emotions.

Studies 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 that some toxins may interfere with brain development. That, they say, could lead to hyperactivity, impulsive behavior, and trouble paying attention. Although it’s been debated, research does not show that ADHD is linked to eating too much sugar or watching a lot of TV.

Brain Activity: Studies show that brain chemicals, called neurotransmitters, don’t work the same in children and adults with ADD/ADHD. There also tend to be differences in the way nerve pathways work.

Certain parts of the brain may be less active or smaller in children with ADHD than those without the disorder.

The brain chemical dopamine may also play a role. It carries signals between nerves in the brain and is linked to movement, sleep, mood, attention, and learning.