Causes of & Risk Factors for ADHD

Written by the Healthline Editorial Team | Published on November 26, 2014
Medically Reviewed by Brenda B. Spriggs, MD, MPH, FACP on November 26, 2014

What Factors Contribute to ADHD?

ADHD is a neurobehavioral disorder. According to the Centers for Disease Control and Prevention (CDC), about 5 percent of children in the United States have ADHD. It affects the way in which a person’s brain processes information and, in turn, influences behavior. The exact cause of ADHD is unknown. According to the Mayo Clinic, researchers believe that genetics, nutrition, brain development, and other factors play a significant role.

Genes and ADHD

There is strong evidence that a person’s genes influence ADHD. In the few studies conducted with twins, researchers have consistently found that ADHD runs in families. It has been found to especially affect close relatives of people with ADHD. If your mother or father has ADHD, you and your siblings are more likely to have the disorder.

No one has yet been able to determine exactly which genes influence ADHD. Some studies have discovered a connection between ADHD and the DRD4 gene. Preliminary research indicates that this gene affects dopamine receptors in the brain. Some people with ADHD have a variation of this gene. This fact leads experts to believe it plays a role in the development of the condition. Still, researchers believe there is more than one gene responsible for ADHD.

It’s important to note that ADHD has been diagnosed in individuals who have no family history of the condition. A person’s environment and a combination of other factors can also influence whether or not you develop this disorder.

Neurotoxins Linked to ADHD

According to Beyond Pesticides, researchers have also found a connection between ADHD and certain common neurotoxic chemicals, namely lead and certain pesticides. Lead exposure in children under age six can hamper brain development, leading to learning disorders including ADHD. 

Exposure to organophosphate pesticides has also been linked to ADHD. These pesticides are chemicals sprayed on lawns and agricultural products. They include corn, apples, pears, grapes, berries, and peaches. Organophosphates are believed to disrupt the neurotransmitter acetylcholine in a child’s developing brain. This key neurotransmitter is responsible for controlling memory, attention, awareness, perception, reasoning, and judgment.

Nutrition and ADHD Symptoms

According to the Mayo Clinic, some studies suggest that certain food dyes and preservatives may cause hyperactivity in some children. Foods with artificial coloring include most processed and packaged snack foods. Sodium benzoate preservative is found in fruit pies, jams, soft drinks, and relishes. Researchers have not determined exactly how these ingredients influence ADHD, only that they appear to worsen its symptoms.

Smoking and Alcohol Use During Pregnancy

Perhaps the strongest link between the environment and ADHD occurs before a child is born. According to the CDC, prenatal exposure to smoking is associated with the behaviors of children with ADHD. Nicotine can affect the same dopamine receptors influenced by the DRD4 gene. A study published by the University of Nebraska suggests that children who were exposed to alcohol and drugs while in the womb were more likely to have ADHD.

Common Myths: What Doesn’t Cause ADHD

There are many myths about what causes ADHD. Research has found no evidence that ADHD is caused by:

  • consuming excessive amounts of sugar
  • TV watching
  • video game playing
  • poverty
  • poor parenting

These factors can worsen ADHD symptoms. However, none of these factors have been proven to directly cause ADHD.

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