I often get parents coming into my office asking why their child is developing Attention Deficit Hyperactive Disorder (ADHD – formerly known as ADD). The truth is: scientists don’t fully understand why some children might develop ADHD, and why other children do not – but there have been studies done that suggest that genetics and environmental exposures play a large role.
In my family practice, I have many parents come to me concerned that because they have ADHD in their family, their child may develop ADHD. What I do tell parents is that ADHD is inherited to some extent. Some studies suggest that ADHD has 76% “heritability,” which means that genetics play a large role in developing ADHD. A study published in a “Current Psychiatry Reports” suggests that if a child has a sibling or parent with ADHD their risk of having ADHD is 2-8x higher than a child whose siblings or parents do not have the disorder.
Based on current research, there is no single specific gene that is involved in developing ADHD, but rather multiple genes. What I also tell parents, is that just because somebody has a gene for a certain disease or disorder does not mean that they will absolutely develop the disease or disorder. For example, some people have the BRCA gene for breast cancer, but never develop breast cancer in their lifetime. Genes are sometimes activated by a process where exposures in our environment may turn on (or off) a specific gene, activating a specific disease or disorder.
The same is true about ADHD, where there are a few studied factors that may influence the expression of the “ADHD” genes. These factors include exposure to certain chemicals during pregnancy and/or childhood, such as:
1) Cigarette smoke
2) Alcohol exposure
3) Lead (an environmental toxin sometimes found in older homes, paints, or pipes)
4) Polychlorinated biphenyls or “PCBs” (an environmental toxin produced from automobile and railroad transformers and plastic production that is now banned due to its known negative health effects).
Based on this medical evidence, what I often tell moms is to avoid smoking cigarettes, drinking alcohol, or any exposures to lead and PCBs (as much as you can) while pregnant and breastfeeding.
Advances in genetic studies of attention-deficit/hyperactivity disorder. Smith AK, Mick E, Faraone SV. Curr Psychiatry Rep. 2009 Apr;11(2):143-8. Department of Psychiatry, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.