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The ADD/ADHD Brain

he ADD/ADHD brain functions differently than a "regular" brain. It is physically smaller (about 3-4% smaller), and works in a different way. One area of the brain is particularly affected by ADD/ADHD: the front-subcortical system.

Executive Functions

Researchers have found that children with ADD/ADHD often have "executive function" impairments.

An "executive function" is like a factory foreman for the brain. Like a foreman organizing his workers, the brain's "executive functions" make sure that all the parts of the brain are organized, working hard, and cooperating with other parts of the brain to get work done.

The brain's executive functions control many aspects of school and job performance. They must:

  • hold information and assign it to the correct parts of the brain
  • get different parts of the brain started when tasks arise
  • control emotion and frustration, making sure that they do not get in the way of the brain's tasks
  • control "self-talk" (e.g., thinking to yourself, "I better get started on this homework if I want to be done in time.")
  • direct complex problem-solving by sorting information to different parts of the brain and integrating the results into a new idea

If a child's executive functions are not working properly, the brain is not organized, and the quality of work decreases.

Level of Activity

The ADD/ADHD brain is less active than a normal brain. This might be surprising, since the ADHD child is usually far more active than other children.

Researchers can observe how active the brain is by using a high-tech device called a Positron Emission Tomography Scan—a PET scan. Using a PET scan, which is somewhat like an X-ray for the brain, scientists can measure the amounts of glucose that different areas of the brain are using. Glucose is the brain's main source of energy, so when one part of the brain is working hard, it consumes more glucose.

Scientists at the National Institute of Mental Health used PET scans to monitor the brain activities of people with and without ADD/ADHD. They found that people with ADD/ADHD have brains that are less active than others' brains. Specifically, the parts of the brain that control impulses and attention were significantly less active in people with ADD/ADHD.

People with ADD/ADHD notice this brain inactivity in their daily lives. They notice that their attention drifts off all the time when they're doing boring and routine tasks, and often complain that they are trying to think through a fog.

Brain Influences

The brain is a complex machine and ADD/ADHD a subtle disorder. We know that the ADD/ADHD brain is working too slowly, but we don't know why. Scientists, however, have identified several factors that influence ADD/ADHD in the brain.

Pre-Natal Exposure: A major influence on the brain is pre-natal exposure to drugs, alcohol, or cigarettes. Babies who are exposed to drugs, alcohol, or cigarettes while in the womb frequently develop ADD/ADHD symptoms in early childhood. For a more complete discussion of the effects of pre-natal exposure to drugs, alcohol, and cigarettes, please visit Hardy Brain's Online Resource Center.

Toxins: Another possible influence on ADD/ADHD may be environmental toxins. Scientists have found that animals exposed to high levels of toxins such as lead often develop ADD/ADHD-like symptoms. They suggest that lead from gasoline-contaminated dirt and some types of paint and water pipes may cause a child to develop ADD/ADHD. However, only a few cases of this kind of ADD/ADHD have been found.

Genetic Influences: Another major influence on ADD/ADHD may lie in a child's genes. Researchers have found that most children with ADD/ADHD have a close relative who also has the disorder or other disorders. When one identical twin has ADD/ADHD, the other twin almost always has it too. Also, fathers who had ADD/ADHD as children have a 30% chance of having ADD/ADHD children. Researchers at the National Institute of Mental Health are now attempting to track down an "ADD/ADHD-gene," though whether such a gene even exists, no one knows.

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