CAUSES OF ADD

Health professionals stress that no one knows what causes ADD. There are too many possibilities to pin down the cause with certainty. The causes of ADD stem from biological sources not home environmental or parental ability.

Over the last decades, scientists have come up with possible theories about what causes ADD. Some of these theories have led to dead ends, some to exciting new avenues of investigation. One disappointing theory was that all attention disorders and learning disabilities were caused by minor head injuries or undetectable damage to the brain, perhaps from early infection or complications at birth. Based on this theory, for many years both disorders were called “minimal brain damage” or “minimal brain dysfunction.”

Although certain types of head injury can explain some cases of attention disorder, the theory was rejected because it could explain only a very small number of cases. Not everyone with ADD has a history of head trauma or birth complications. Another theory was that refined sugar and food additives make children hyperactive and inattentive. As a result, parents were encouraged to stop serving children foods containing artificial flavorings, preservatives, and sugars. However, this theory, too, came under question. In 1982, the National Institutes of Health (NIH), the Federal agency responsible for biomedical research, held a major scientific conference to discuss the issue. After studying the data, the scientists concluded that the restricted diet only seemed to help about 5 percent of children with ADD, mostly either young children or children with food allergies.

ADD cannot be induced by a child watching too much TV, eating too much sugar, attending a sub-par school, or through bad parenting.

In recent years, as new tools and techniques for studying the brain have been developed, scientists have been able to test more theories about what causes ADD. Using one such technique, NIMH scientists demonstrated a link between a person’s ability to pay continued attention and the level of activity in the brain. The investigators found important differences between people who have ADD and those who don’t. In people with ADD, the brain areas that control attention used less glucose, indicating that they were less active. It appears from this research that a lower level of activity in some parts of the brain may cause inattention.

Brain scan images produced by positron emission tomography (PET) show differences between an adult with Attention Deficit Hyperactivity Disorder and an adult free of the disease.

Researchers are also searching for other differences between those who have and do not have ADD. Research on how the brain normally develops in the fetus offers some clues about what may disrupt the process. Throughout pregnancy and continuing into the first year of life, the brain is constantly developing. It begins its growth from a few all-purpose cells and evolves into a complex organ made of billions of specialized, interconnected nerve cells. By studying brain development in animals and humans, scientists are gaining a better understanding of how the brain works when the nerve cells are connected correctly and incorrectly.

Scientists at NIMH and other research institutions are tracking clues to determine what might prevent nerve cells from forming the proper connections. Some of the factors they are studying include drug use during pregnancy, toxins, and genetics. Research shows that a mother’s use of cigarettes, alcohol, or other drugs during pregnancy may have damaging effects on the unborn child. These substances may be dangerous to the fetus’s developing brain. It appears that alcohol and the nicotine in cigarettes may distort developing nerve cells.

For example, heavy alcohol use during pregnancy as been linked to fetal alcohol syndrome (FAS), a condition that can lead to low birth weight, intellectual impairment, and certain physical defects. Many children born with FAS show much the same hyperactivity, inattention, and impulsivity as children with ADD. Drugs such as crack cocaine seem to affect the normal development of brain receptors. These brain cell parts help to transmit incoming signals from our skin, eyes, and ears, and help control our responses to the environment.

Current research suggests that drug abuse may harm these receptors. Some scientists believe that such damage may lead to ADD. Toxins in the environment may also disrupt brain development or brain processes, which may lead to ADD. Lead is one such possible toxin. It is found in dust, soil, and flaking paint in areas where leaded gasoline and paint were once used. It is also present in some water pipes. Some animal studies suggest that children exposed to lead may develop symptoms associated with ADD, but only a few cases have actually been found.

Other research shows that attention disorders tend to run in families, so there are likely to be genetic influences. Children who have ADD usually have at least one close relative who also has ADD. And at least one-third of all fathers who had ADD in their youth bear children who have ADD. Even more convincing: the majority of identical twins share the trait.

The neurotransmitter dopamine has been implicated in ADD.  Dopamine is the “feel good” chemical in the brain which is responsible for our ability to concentrate as well as our feelings of happiness.  Just about all mood-altering drugs work on dopamine, including alcohol, cigarettes, caffeine, heroin, and cocaine, as do stimulant medications for ADD.  Dopamine activity increases naturally in response to mental or physical stimulation, this explains why everyone, especially those diagnosed with ADD can focus much better after exercise or during an emergency. In fact, it is said that many of the people involved in emergency response are ADD, such as firemen and ER physicians. A study in Scientific Daily has shown that a group of adults diagnosed with ADD had reduced levels of dopamine in the brain.

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Davisson Clinic, LLC
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