There are so many theories out there circulating about what actually causes ADHD, that I decided to put together this "ten-part series of articles". This is the first article. Theory 1: lead causes ADHD, or may be a contributing factor.
Joel Nigg, Ph.D., a professor at Michigan State University, has recently suggested, through a new study, that even low levels of lead may contribute to ADHD.
Researchers, headed by Nigg, selected 150 children aged 8-17 to participate in the study. One third of the participants had ADHD, combined type; One third had ADHD inattentive type; and the remainder did not have ADHD, and could therefore serve as controls.
What researchers discovered after testing their lead levels was very revealing. Blood levels were much higher in the Children with ADHD, combined type, than in the control children, but not in the children with ADHD inattentive type; leading Nigg and the researchers to believe that low lead levels in the blood may in fact play a role in the hyperactivity component of ADHD.
Nigg pointed out that almost all Americans have a low-level exposure to lead, a well known neurotoxin, making the metal an ideal candidate for causing ADHD.
Nigg's explanation on how lead could cause ADHD is that lead attaches to sites in the brain's striatum and frontal cortex where the metal causes specific genes to turn on or remain inactive. He theorizes that this disrupts brain activity and alters psychological processes supported by these neurons, contributing to hyperactivity.
Recently, researchers from Johns Hopkins University conducted an experiment on rats to see how lead would affect the developing structure of the neocortex region in the brain. The neocortex region of the brain has layers of nerve cells which process information. This region of the brain is highly vulnerable to environmental stimuli in early childhood.
Researchers added low doses of lead to a nursing rats drinking water for ten days, to see what affect this would have on the nursing rat pups. They found structural changes in the brains of the nursing rat pups. The rat pups who were exposed showed up to 12% diminished size of this region of the brain. When they increased the dose of lead, this area of brain development was stunted even more. At even higher levels, lead can actually shrink the brain. Researchers concluded that heavy metal stunts the preliminary cells in the brain.
Higher lead levels may actually lead to delinquent behavior, according to Herbert L. Needleman, M.D., (recipient of the 1995 Heinz Award in the Environment for his efforts to protect children from toxic exposure), of the University of Pittsburgh. He studied the lead levels of juvenile delinquents and found they had seven times the amount of bone lead than the control group. Males are twice as likely, and females almost eight times more likely to be arrested as a juvenile delinquent. "Early lead exposure accounts for 11% and 37% of arrested delinquents", claims Dr. Needleman. He urges that reducing lead exposure should be a primary prevention strategy against delinquency in adolescents.
According to the EPA, drinking water is estimated to comprise about 10-20% of total lead exposure in children; in infants fed with baby formulas using tap water this proportion rises to 40-60%. Surprisingly, the newer the home, the greater the risk of lead in the drinking water due to the greater degree of leaching from newly-joined copper pipe. There are now lead-free solders available; ask your plumber what type was used when your house was built.
Other sources of exposure to lead include lead-based paint, contaminated soil, food, dust, children's toys, bullets, some engine fuels (although, countries are now increasingly using unleaded gasoline), working in lead mines, and it is also used in production of jewelry, and eating and drinking utensils.
Lead can enter our body through the skin, ingestion, or inhalation. Lead poisoning, built up over time, causes lowered I.Q., slowed growth, behavior problems, attention problems, irritability, aggressive behavior, headaches, constipation, and anemia, just to name a few. When you look at the symptoms of lead poisoning over time and ADHD, there are a lot of similarities.
There are no implications that advocate intervening with medication to lower lead levels. These studies emphasize the need for public health officials and the public to be aware of these high environmental risk areas for lead exposure so these areas can be eliminated or avoided. Tougher legislation needs to be passed concerning the use of lead in common household products.
Some proposals for preventing lead poisoning and its effects include removing lead-based gasoline throughout the world, passing laws to reduce the amount of lead emitted through incinerators, removing the lead-based paint from houses built prior to 1960, inspecting pipes, candles, fixtures, soldering, television sets, and computer monitors.
Lead is a dangerous neurotoxin that attacks the nervous system and stunts developing brains in young children. It is a base element that doesn't break down in the environment. This puts all of our children at risk.
Recently, there have been many recalls of children's products because of unsafe amounts of lead. This is a step in the right direction, but so much more needs to be done.
For more information about the threat of lead exposure to healthy childhood development, read Developmental Disorders of Toxic Origin.
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