The exact cause of attention deficit hyperactivity disorder (ADHD) is not known. But inherited genetic factors are likely responsible. Ongoing research is focused on identifying genes that cause a person to be susceptible to ADHD.

Using various imaging tests, researchers have been able to observe the brain at work. They have found a possible link between ADHD and:

• Brain structure.
• The function of chemicals in the brain that help regulate attention and activity (dopamine and norepinephrine).
• Differences in function of some of the areas of the brain that affect attention and impulse control.

Also, research shows that a mother's use of cigarettes, alcohol, or other drugs during pregnancy may increase the risk for ADHD. Some studies suggest that exposure to lead may cause symptoms associated with ADHD.¹

Although many parents believe that foods with sugar and food additives make their children more hyperactive, these foods have not been shown to cause ADHD. In a comprehensive review of research, the U.S. National Institutes of Health (NIH) found that restricted diets seemed to help only about 5% of children with ADHD, mostly either young children or children with food allergies. Other research has shown that sugar is not related to ADHD.¹

A study by the National Institute of Mental Health found that certain parts of the brains of children with ADHD develop normally but about 3 years later than in children without ADHD.² This may be why some children seem to grow out of the disorder.

Some people have misconceptions about ADHD, such as that children with ADHD are lazy or dumb. Talk with a doctor about questions or concerns you have about these issues.