While the exact causes of ADHD remain a mystery, researchers have identified several factors that may play a role.
For example, studies show that Attention Deficit Hyperactivity Disorder tends to run in families.
About one in four children with Attention Deficit Hyperactivity Disorder (ADD/ADHD) have at least one relative with the disorder (Centers for Disease Control and Prevention, 2007).
In addition, recent studies of twins link genes with Attention Deficit Hyperactivity Disorder.
In such instances, if one twin suffers from Attention Deficit Hyperactivity Disorder, the other twin is likely to suffer from the condition (Centers for Disease Control and Prevention, 2007).
Pregnant women who smoke are at increased risk of having children with ADHD (Centers for Disease Control and Prevention, 2008.) In addition, alcohol or drug abuse during pregnancy may reduce activity of the neurons that produce neurotransmitters.
Pregnant women who are or were exposed to environmental poisons such as polychlorinated biphenyls (PCBs) may be more likely to have children with symptoms of ADHD. (PCBs are industrial chemicals that were widely used up until the 1970s.)
More recently, new studies have indicated that ADHD may be linked to prenatal exposure to pesticides and organophosphates. (See ADHD Linked To Pesticides). Pesticides are increasingly being investigated as one of the potential causes of ADHD.
Preschool children exposed to environmental hazards and toxins are at increased risk of developmental and behavioral problems. Exposure to lead, which is found mainly in paint and pipes in older buildings, has been linked to disruptive behavior, violent behavior, and shortened attention spans. Lead paint chips tend to have a sweet taste which attracts young children who often enjoy teething on a variety of objects. In addition, exposure to PCBs (polychlorinated biphenyls) in infancy may also increase a child's risk of developing ADHD (Centers for Disease Control and Prevention, 2008.)
Brain scans have revealed important differences in the structure and brain activity of people with ADHD. There appears to be less activity in the areas of the brain that control activity and attention.
Research does not support popularly held myths that ADHD is caused by consuming too much sugar, watching too much television, poor parenting, or social and environmental factors such as poverty or family upheaval.
Of course, these environmental factors may worsen the symptoms of ADHD but the evidence is not strong enough to conclude that are a causal component of ADHD. For more information see this article about the ADHD Food Link.