What Are the Possible Causes of ADHD?

ADHD is a real medical condition that may run in families. So, for instance, if your child has ADHD, there is a higher risk that you may have ADHD, too. The exact cause of ADHD is unknown. A high degree of heritability does not mean that all adults with ADHD will have children with the disorder. Another thing to keep in mind is that though ADHD begins in childhood, it can affect you throughout your life. In fact, approximately 50-66% of children diagnosed with ADHD in childhood may continue to have ADHD symptoms as adults.

Do people outgrow ADHD?

Many people tend to think of ADHD as a childhood disorder. However, the symptoms affect children, teens, and adults. In fact, an estimated 11% (6.4 million) of US school-aged children have been diagnosed with ADHD in their lifetime.* Additionally, an estimated 4.4% of adults in the US have ADHD.

When using a calculation based on the full US adult population aged 18 and over, approximately 10.5 million adults in the US are estimated to have ADHD.

*Based on the 2011/12 National Survey of Children’s Health, in which parents were asked if a health care practitioner had ever told them their child had ADD or ADHD.

Based on the National Comorbidity Survey Replication of 3,199 adults aged 18 to 44 years conducted from 2001 to 2003.

Based on the National Comorbidity Survey Replication of 3,199 adults aged 18 to 44 years conducted from 2001 to 2003 and applied to the full US population in 2011 aged 18 and over.



Brain Chemistry, Genetics, and Environment

The exact cause of ADHD is unknown, but researchers believe the disorder may be caused by one or more factors. These include brain chemistry. ADHD is thought to possibly be caused by an imbalance of 2 of the brain’s chemical messengers, or neurotransmitters. Researchers think that these chemicals might play an important role in ADHD. In addition, genetics may also contribute to ADHD. Research suggests that ADHD may run in families. Parents of children with ADHD may be at higher risk of having ADHD themselves. However, this does not mean that every member of a family will have the disorder. If you're concerned about ADHD in your family, you may want to start gathering information by talking with your relatives. Finally, certain environmental factors, such as smoking during pregnancy or complications during pregnancy could lead to the development of ADHD.

What parts of the brain are thought to be involved in ADHD?

We do not know exactly why people develop ADHD. It may be related to problems with a part of the brain called the prefrontal cortex. The picture below shows the different parts of the prefrontal cortex that control attention, behavior, and judgment. Certain regions of the prefrontal cortex may not function properly in people with ADHD. 

1_2_BRAINPin_Mobile 1_2_BRAINPin

If the areas of the prefrontal cortex shown in green, blue, or brown are impaired, a person with ADHD may have symptoms such as inattention or impulsive or hyperactive behavior.

What causes ADHD?

We don't know exactly what causes ADHD. Researchers believe ADHD may be caused by one or more of the following factors:

  • ADHD is thought to be caused by an imbalance of two chemical messengers, or neurotransmitters, in the brain. Researchers think that these chemicals might play an important role in ADHD.
  • Research suggests that ADHD may run in families. However, this does not mean that all children in a family will have the disorder.
  • Certain external factors, such as smoking during pregnancy or complications during pregnancy, may contribute to ADHD.