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Mark Hutten, M.A.
Re: Causes of Attention Deficit Hyperactivity Disorder (ADHD)

What Causes ADHD?

Scientists are not sure what causes ADHD, although many studies suggest that genes play a large role. Like many
other illnesses, ADHD probably results from a combination of factors. In addition to genetics, researchers are looking
at possible environmental factors, and are studying how brain injuries, nutrition, and the social environment might
contribute to ADHD.
•   Brain injuries. Kids who have suffered a brain injury
may show some behaviors similar to those of ADHD.
However, only a small percentage of kids with ADHD
have suffered a traumatic brain injury.
Environmental factors. Studies suggest a potential
link between cigarette smoking and alcohol use during
pregnancy and ADHD in kids.5,6 In addition,
preschoolers who are exposed to high levels of lead,
which can sometimes be found in plumbing fixtures or
paint in old buildings, may have a higher risk of
developing ADHD.7
Food additives. Recent British research indicates a
possible link between consumption of certain food
additives like artificial colors or preservatives, and an
increase in activity.11 Research is under way to confirm
the findings and to learn more about how food additives
may affect hyperactivity.
•   Genes. Inherited from our moms and dads, genes are the "blueprints" for who we are. Results from several
international studies of twins show that ADHD often runs in families. Researchers are looking at several genes that
may make people more likely to develop the disorder.2,3 Knowing the genes involved may one day help researchers
prevent the disorder before symptoms develop. Learning about specific genes could also lead to better treatments.
Kids with ADHD who carry a particular version of a certain gene have thinner brain tissue in the areas of the brain
associated with attention. This NIMH research showed that the difference was not permanent, however, and as kids
with this gene grew up, the brain developed to a normal level of thickness. Their ADHD symptoms also improved.4
•   Sugar. The idea that refined sugar causes ADHD or
makes symptoms worse is popular, but more research
discounts this theory than supports it. In one study,
researchers gave kids foods containing either sugar or a
sugar substitute every other day. The kids who received
sugar showed no different behavior or learning capabilities
than those who received the sugar substitute.8 Another
study in which kids were given higher than average amounts
of sugar or sugar substitutes showed similar results.9In
another study, kids who were considered sugar-sensitive by
their mothers were given the sugar substitute aspartame,
also known as Nutrasweet. Although all the kids got
aspartame, half their mothers were told their kids were given
sugar, and the other half were told their kids were given
aspartame. The mothers who thought their kids had gotten
sugar rated them as more hyperactive than the other kids
and were more critical of their behavior, compared to
mothers who thought their kids received aspartame.10