The exact cause of attention deficit hyperactivity disorder (ADHD) is unknown, although many studies suggest that the disorder has a very strong neurological basis. In other words, ADHD is probably caused by the way brain chemicals (neurotransmitters such as dopamine) interact in an afflicted person’s body. Because neurotransmitter activity is very much determined by genetics, it seems clear that heredity plays a significant role in ADHD. However, because the genes involved seem to target a relatively wide range of brain functions, scientists believe that ADHD is a complex genetic trait that probably results from a multifaceted combination of genetics and environmental factors.


Studies done on twins show that about 75 percent of ADHD symptoms can be attributed to genetic factors.  To this point, however, no single gene has been pinpointed as the cause of ADHD. Scientists believe that a complex interaction among a number of genes can affect chemicals in the brain—specifically dopamine—that, in turn, can cause certain behavioral traits. 

Environmental Factors

Although the exact mechanisms of ADHD remain unclear, a few environmental factors that increase the risk of a diagnosis have been singled out. For example, exposure to alcohol and tobacco smoke during pregnancy has been shown to increase a child’s risk of developing ADHD, as has early exposure to lead products.


Recent British studies found evidence that artificial colors and the preservative sodium benzoate each led to increased hyperactivity in children. Researchers in the field continue to study the effects of these and other food additives on behavioral disorders in children.

Risk Factors

Unfortunately, the risk factors for attention deficit hyperactivity disorder (ADHD) tend to be either genetic or related to environmental factors experienced during pregnancy or infancy and are therefore largely outside of an individual’s control. 


A family history of ADHD or other mental health issues may raise ADHD risk. Studies show that approximately 75 percent of ADHD symptoms are genetically determined. 


Males are nearly twice as likely to be diagnosed as females.

Prenatal Health

Research shows that a mother's use of cigarettes, alcohol, or other drugs during pregnancy may increase the risk of ADHD.

Exposure to Lead

Some studies suggest that lead exposure may cause symptoms associated with ADHD.

Premature Birth

Studies show that children born prematurely have a significantly higher risk of developing ADHD.