There are still many unanswered questions as to the cause of ADD. Over the years the presence of ADD has been weakly associated with a variety of conditions including: prenatal and/or perinatal trauma, maturational delay, environmentally caused toxicity such as fetal alcohol syndrome or lead toxicity, and food allergies. History of such conditions may be found in some individuals with ADD, however, in most cases there is no history of any of the above.

Recently, researchers have turned their attention to altered brain biochemistry as a cause of ADD and presume differences in biochemistry may be the cause of poor regulation of attention, impulsivity and motor activity. A recent landmark study by Dr. Alan Zametkin and researchers at NIMH have traced ADD for the first time to a specific metabolic abnormality in the brain. A great deal more research has to be done to reach more definitive answers.