We still don't know the exact causes of ADHD.
Studies consistently suggest that ADHD is inherited. But in the last few years, research has also linked ADHD to prenatal exposure to environmental toxins such as bisphenol A and phthalates (key ingredients in a wide range of products from cosmetics to plastic shower curtains), as well as lead (found in old paint) and pesticides (used in homes and schools and on farms). "The science is still very new and the studies, though strong, must be repeated by other researchers," says pediatrician and epidemiologist Philip Landrigan, M.D., director of the Children's Environmental Health Center, in New York City, and a member of the Parents Board of Advisors. "But children are especially sensitive to environmental toxins and we need to pay much more attention to how and when they are exposed."
A theory has persisted that food dyes contribute to ADHD, and some parents insist that once their kids are on a diet that eliminates dyes and preservatives, their ADHD symptoms improve dramatically. But the mainstream medical community is unconvinced. In 2011, after reviewing 50-plus studies linking food additives and ADHD, the FDA's Food Advisory Committee concluded there is not enough solid data to definitively say that artificial food dyes can trigger hyperactivity in kids. Adds Dr. Kurtz, "At this time, we have no reliable evidence showing that avoiding products with sugars, dyes, or additives will lessen problematic symptoms."