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What causes ADHD?


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October 24, 2013 3:58PM

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While there is still considerable controversy about the specific cause or causes of ADHD, the one tested and demonstrated fact is that ADHD correlates with a chemical imbalance in the brain. PET scans of the brains of ADHD subjects and brains of individuals not subject to ADHD show a pronounced difference in the levels of neurotransmitters such as dopamine. Chemicals which stimulate the production and uptake of these neurotransmitters seem to help many of those who are ADHD.

Quite a few different hypotheses have been advanced about what actually causes ADHD, but the only clear factor that has been reproducibly correlated with it is genetics. Children with a parent, grandparent, or other close relative with ADHD have a higher likelihood of also being ADHD, even if they are not raised by those parents, such as adopted children. Some hypotheses that have been advanced are:

Drug use by the mother or father - if this caused genetic damage or organic damage to the brain, it might make sense. It is also possible that damage done to a foetus by drugs could manifest ADHD-like symptoms without it actually being ADHD. Fetal alcohol syndrome would fall in this category.

Bad diet - this one is exceedingly difficult to investigate since diets are so varied. Hyperactivity related to excess sugar consumption (and consequently an abundance of quick energy for a child) might look like ADHD to an adult trying to deal with the kid, but it would not really be ADHD.

Environmental poisons - like bad diet, this is exceedingly difficult to establish since it is so difficult to identify everything a child or their parent may have been exposed to. Also like drug use, damage done by a poison can manifest symptoms which are similar to ADHD. Lead poisoning, for example, causes brain damage but does not result in all the symptoms of ADHD.

Too much viewing of TV or other video screens - no, I'm not kidding. There are inconclusive studies that suggest that kids who watch large quantities of the flickering images of video screens have their brains trained to respond abnormally to stimuli.

One of the complicating factors in determining the cause or causes of ADHD is that it has a strong behavioral component. Most people who are successfully coping with ADHD have included a large dose of behavior modification in their overall strategy. Since the same outward behavior (lack of attention, lack of responsibility, distractability, etc.) can stem from a lot of other causes than ADHD, other conditions often get conflated with ADHD and muddy the water for researchers trying to identify a cause.

ADHD is the imbalance in certain brain chemicals (called neurotransmitters) that are needed for paying attention and controlling behavior. Two of these neurotransmitters are norepinephrine and dopamine. Recent studies are also demonstrating difference between brain activity of people with ADHD, as compared to people without ADHD. People with ADHD have less activity in certain areas of the brain that help you to pay attention. The medications that are used to treat ADHD work by increasing the levels of these neurotransmitters in the brain.

ADD/ADHD may be inherited. Research shows that ADD/ADHD tends to run in families so there are likely to be genetic influences. Children who have ADHD usually have at least one close relative who also has ADHD. And at least one-third of all fathers who had ADHD in their youth have children with ADHD. Even more convincing regarding a possible genetic link is that when one twin of an identical twin pair has the disorder, the other is likely to have it too.

Here are more answers and opinions from other FAQ Farmers:

  • I've encountered four mothers of ADHD children who admitted the use of hallucinogenic drugs before and during pregnancy (cocaine, LSD or "magic mushrooms"). This is not a confirmed cause but is a strong possibility. Lead poison of the fetus could be related to the use of cocaine or hallucinogenics since lead is used in the process of fabrication. Researcher at MCGill University MTL Canada. Of course, not all mothers of ADHD children used drugs. Most did not.
  • In most cases, it is caused by an underlying condition that encompasses all of the symptoms of ADD/ADHD. There exists a lack of communication between fields of research.
  • AD/HD is generally inherited and runs in families. About 1 percent of people develop it for other reasons (e.g. toxins, possibly environmental, introduced to the developing fetus). Although a possible cause, it is unlikely that many people develop the syndrome purely as the result of hallucinogenic drug use by the mother during pregnancy. There is also the possibility that the mother used such substances because of the lack of inhibition which is a symptom of adult AD/HD. In other words, both the child's and the mother's behaviour may stem from the same genetic cause. Brain scans of those who suffer from the disorder show abnormal functioning in areas related to the ability to select what stimuli to attend to or ignore. The "racing brain" is a symptom indicating that the person doesn't know how to monitor, sift and regulate their thoughts and actions. While some people with AD/HD are very bright, some aren't.