What Is ADHD?

Published April 7, 2020

Attention deficit hyperactivity disorder (ADHD) is one of the most common behavioral disorders among children.

ADHD is a condition that affects children and adults, but the symptoms, which differ from person to person, always begin in childhood. These behaviors generally interfere with academic and social success and cause many difficult challenges.

About four million American children— up to 11 percent of school age children have ADHD.

ADHD is usually discovered during the early school years when a child begins to struggle with concentration or attention to a task.

Common behaviors associated with ADHD include: 

  • Inability to maintain attention and stay on task
  • Hyperactive
  • Impulsive behavior
  • Inability to sit still, fidgety
  • Poor listening skills
  • Difficulty following directions
  • Loses and misplaces things often
  • Careless mistakes in homework and class work
  • Talks excessively and interrupts others
  • Difficulty playing quietly
  • Difficulty with organizing and prioritizing
  • Moves from one activity to another

What causes ADHD?

While ADHD is one of the most common behavioral disorders diagnosed in childhood, it is a definitive cause is still unknown.

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


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

Factors related to pregnancy and birth

  • Children are at a higher risk of ADHD if they:
    • Were born premature
    • Had a low birth weight
    • If the mother had difficult pregnancy

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— leading to hyperactivity, impulsive behavior, and difficulty with attention.

  • The same is true for children with head injuries to the frontal lobe of the brain, the area that controls impulses and emotions.

Brain activity

Studies show that certain parts of the brain may be less active or smaller, in children with ADHD, when compared to those without the disorder. In addition, the brain chemicals, called neurotransmitters, and neural pathways, appear to work differently.

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

Can ADHD be caused by a vision problem?

Many symptoms of ADHD can actually overlap with behaviors that result from an undiagnosed vision problem, such as: difficulty focusing in school, tendency to fidget or squirm in their seats, making careless mistakes, etc. Other visual problems can lead to skipping lines, confusing words and word-order, and generally make it impossible to read accurately.

Studies show that children with vision problems are twice as likely to be diagnosed with ADHD.  

If your child displays behaviors that are typically associated with ADHD, don’t automatically label your child with ADHD— they may have a vision problem.

Many vision problems can be treated through eyeglasses, contact lenses, or a program of vision therapy.  

Schedule a comprehensive vision evaluation with an experienced eye doctor for an accurate diagnosis of a vision problem that may be affecting your child’s behavior. 

How is ADHD diagnosed?

Unfortunately, diagnosing ADHD is complicated. A diagnosis is made on the basis of observable behavioral symptoms in multiple settings.

This means that the professional conducting the evaluation, usually a pediatrician, pediatric neurologist, psychologist, or psychiatrist, must use multiple sources to collect the information needed.

A proper ADHD diagnostic evaluation includes the following elements:

  1. A thorough medical and family history
  2. A physical examination
  3. Interviews with the parents, the child, and the child’s teacher(s)
  4. Behavior rating scales completed by parents and teacher(s)
  5. Observation of the child
  6. A variety of psychological tests to measure I.Q. and social and emotional adjustment, as well as to indicate the presence of specific learning disabilities.

If you think your child may be showing signs of ADHD, and you have ruled out a vision problem, discuss your concerns with your pediatrician. Your doctor will be able to explain how to effectively diagnose ADHD, as well as all of the different treatment options.