The developmental origins of ADHD

I sometimes ponder the quirkiest questions. For example, “Why exactly does cigarette smoke increase the risk of ADHD in children? What do we know about this smoke injury that may help us understand other preventive measures in ADHD? What are the developmental origins of ADHD as they relate to environmental exposures?”
These questions are sometimes like the “Which came first, the chicken or the cgg?” question that still confuses us today. Does hypothetical Mom of ADHD kid smoke because she has ADHD, or does child have ADHD because Mom smoked?? The answer is: Yes, both are correct in some unique ratio.
We know there are genetic predispositions to this disorder.
Twins studies support the highly genetic link in ADHD. If one identical twin has ADHD, there is an 80% chance the other twin will also be affected. Two dopamine genes, DAT1 and DRD4 have been reported to be associated with ADHD by a number of scientists. Others are likely to be discovered and understood as science progresses.
But what about the environmental factors?
Maternal smoking during pregnancy infers a 2.5 x increased risk of ADHD in the child. If the child is a girl, then a 4.5 fold increased risk of ADHD is noted. Interestingly, this vulnerability seen in the girls is unusual in the field of developmental disabilities. These increased risks are mediated by nicotine, which decreases blood flow to the brain by narrowing the uterine blood vessels. The babies are smaller with smaller brains at birth and more likely to have a variety of malformations. Nicotine also increases the number of nicotinic receptors on the brain cells. Beyond nicotine, smoking puts carbon monoxide into the blood and prevents the delivery of oxygen by blood cells. Carbon monoxide levels in cigarette smoke resemble that of automobile exhaust. Smoking reduces the oxygen supply to the infant in the womb, in effect slightly smothering the defenseless baby.  The developing brain is particularly vulnerable to low levels of oxygen, and immaturity of the brain center that regulates breathing could contribute to SIDS. Recent studies of smoking mothers’ infants who died in the womb provide insight into how exposure to smoking may injure developing brains. Besides causing neurological damage by lessening oxygen supply to the developing brain, nicotine may be poisonous to areas of the brain directly involved with heart and breathing regulation.
Beyond carbon monoxide and nicotine, cigarette smoke also includes benzene, a potential carcinogen; ammonia; hydrogen cyanide, which is used in making rat poison; formaldehyde and cadmium.  Studies have not yet determined which of the above toxins are most likely to result in brain changes that lead to ADHD.
The impact of environmental toxins on children’s health has become a major focus by the EPA and the National Institute of Environmental Health Sciences (NIEHS). “The brains of our children are our most precious economic resource, and we haven’t recognized how vulnerable they are,” says Philippe Grandjean, adjunct professor at Harvard School of Public Health and the lead author of the study published in The Lancet ( Volume 369, Issue 9564, Page 821, 10 March 2007”. “We must make protection of the young brain a paramount goal of public health protection. You have only one chance to develop a brain.”
Environmental Toxicology
My point is this. The scientific literature is leading us in the direction of environmental toxicology as we try to understand some of the factors propelling the prevalence of neurodevelopmental disorders into the stratosphere. The environmental toxicant relevant to ADHD that I chose to pick on today was cigarette smoke. However, this is just the surface of the potential stew of toxicants at play in the developing brain.
Therefore, if your child has ADHD, I recommend that you remove toxicants from the environment and from foods, purify home air and eat organic; replenish nutrients commonly depleted (such as iron, vitamin D, zinc, essential fatty acids, antioxidants, etc); balance neurotransmitters with your doctor’s help by supplementing with amino acid building blocks (perhaps 5HTP, GABA, taurine…..), and test your child’s toxic load. In my practice, I recommend hair analyses, provoked urine metal excretion tests, porphyrins testing, and assays for solvents and toxic metals in blood.  Work with your doctor to begin the evaluation for toxicities and the treatment approaches that may follow.
Encourage someone you love to quit smoking and, should the opportunity arise, support labeling cigarettes with warnings similar to those already on bottles of alcohol. Then, take heart that you’re educating yourself to provide a safe and healthy home for optimal brain development, whether you’re trying to develop around ADHD or some other neurodevelopmental disability.
Karen H. Harum, MD, FAAP
Fellow, Neurodevelopmental disabilities
Medical Consultant, Spruce Kids

Spruce Kids

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The "ADHD Mommas" are not medical or mental health professionals, nor an ADHD coach. Any opinions shared here are just that, opinions. I, and the other "ADHD Mommas," are sharing our experiences with our own ADHD children. Please do not re-post or publish any content or photos without a link back to {a mom's view of ADHD}. Have the courtesy to give credit where credit is due. Copyright protected. All rights reserved.

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