Attention Deficit Hyperactivity Disorder: Causes of ADHD

No one knows exactly what causes 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 the disorder. 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 it. 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.

What Doesn’t Cause ADHD

Although it’s been debated, research does not show that ADHD is linked to eating too much sugar or watching a lot of TV.

What Goes On in the Brain

Studies show that brain chemicals, called neurotransmitters, don’t work the same in children and adults with 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.

WebMD Medical Reference Reviewed by Smitha Bhandari, MD on June 07, 2019



CHADD: "What Causes ADHD?;" ”Causes and Brain Chemistry;” and “New Understandings of ADHD.”

The ADHD Genetic Research Study at the National Institutes of Health and the National Health Genome Research Institute: "General Information about ADHD" and “Attention Deficit Hyperactivity Disorder.”

Mayo Clinic: “Attention-deficit/hyperactivity disorder (ADHD) in children.”

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