Genetic and Biological Causes
The causes of attention deficit disorder (ADD) are not clear, and yet it seems that there are many issues that can contribute to someone developing ADD. There seems to be some genetic component to ADD, in that ADD tends to run in families. In some people, however, there seems to be no genetic basis for developing ADD. These cases of ADD may occur due to other causes.
Researchers have been searching for one or several genes that cause ADD. Presently, they are looking into the genes that manufacture the neural transmitter called dopamine. People with ADD and ADHD seem to have lower levels of dopamine, a chemical that helps move information from one neuron to another.
Another possible biological cause of ADD has to do with the size of the brain. A 2002 study discovered that children with ADD had slightly smaller brain volumes than those without ADD, but when the children with ADD were medicated, they had similar brain volumes to those without ADD. The amount of "white matter" in the brain, or connections between different regions of the brain, is also related to ADD. Children with unmediated ADD often have much less white matter than children without ADD.
Maternal smoking and drinking during pregnancy have been linked with ADD in the resulting child. Children who were born after a difficult pregnancy or who had a low birthweight also have a higher chance of developing ADD. In addition, brain injury or exposure to environmental toxins, both in utero and shortly after birth, can increase a child's risk of developing ADD.
Diet can have a strong effect on whether a person shows ADD symptoms. In fact, William Sears describes a disorder that he calls "NDD," or "Nutritional Deficit Disorder." He claims that many cases of supposed ADD could be fixed if the child would make the proper nutritional changes. Examples of foods that should eliminated from the diet of a person exhibiting NDD symptoms include refined sugars and artificial ingredients. Foods that can have a positive effect on ADD symptoms include foods that contain Omega-3 fatty acids (e.g., nuts, seeds, seafood), blueberries, spinach, yogurt, whole grains, and foods containing folate (e.g., leafy greens).
Exposure to lead or other environmental toxins may also affect whether a child develops ADD. Newer paints no longer contain lead, but old paint or plumbing that children come into contact with can contaminate their bodies with lead, leading to a higher chance of developing ADD symptoms. Second-hand smoking has also been linked to ADD.
Again, the causes of attention deficit disorder are still being studied, and researchers are currently unsure about just how much each factor contributes to developing ADD. In time, researchers hope to get a better look at the various factors that seem to contribute to an ADD diagnosis.