05-23-2009, 05:50 PM
Functional defects can affect the nervous system, immune system, reproductive system, endocrine system, or other systems of the body, and may not become apparent for months or years. These may include, for example, mental retardation, autism, attention deficit hyperactivity disorder (ADHD), some types of blindness and deafness, some immunological problems, and some degenerative disorders. AD/HD is a disorder that makes it hard for children to sit still, control their behavior, and pay attention. It is usually diagnosed before the age of 7, but not always. Doctors aren't sure what causes AD/HD, but studies support the theory that it is related to an imbalance of certain chemicals in the brain called neurotransmitters.
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