Causes

ADHD is a neurobehavioral disorder that affects approximately 5.2 million children in the United States (CDC, 2012). ADHD affects the way in which a person’s brain processes information and, in turn, influences behavior. The exact cause of ADHD is unknown. However, 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 found that ADHD runs in families (NIMH, 2012). 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, however, have discovered a connection between ADHD and the DRD4 gene (Holmes et al., 2002). These studies have led expert to believe this gene plays a role in the development of the condition. Still, researchers believe there is more than one gene responsible for ADHD. 

It is 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

Researchers have also found a connection between ADHD and certain common neurotoxic chemicals, namely lead and certain pesticides. Lead exposure in children can hamper brain development, leading to learning disorders including ADHD.

Exposure to organophosphate pesticides has also been linked to ADHD (Bouchard et al., 2010). These pesticides are chemicals sprayed on lawns and agricultural products. They include corn, apples, pears, grapes, berries, and peaches. Children who had high levels of these pesticides in their systems were in some cases twice as likely to have ADHD as children who did not. 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.

Smoking and Alcohol Use During Pregnancy

Perhaps the strongest link between the environment and ADHD occurs before a child is born. Research consistently shows a strong link between smoking and alcohol use during pregnancy and ADHD. According to a recent study by Washington University in St. Louis, if a mother is genetically predisposed to the disorder and smokes during pregnancy, her child is six to nine times more likely to develop ADHD or have more severe ADHD symptoms (Neuman et al., 2007). Nicotine can affect the same dopamine receptors influenced by the DRD4 gene.

Nutrition and ADHD Symptoms

A 2007 study by British researches showed that children who consume foods with artificial coloring or a sodium benzoate preservative were more hyperactive than those who did not consume these additives (McCann et al, 2007). 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 exacerbate its symptoms.

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