defective

de·fec·tive (d-fktv)

n.

1. Having an imperfection or malformation.

2. Lacking or deficient in some physical or mental function.

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defective

[difek′tiv]

Etymology: L, defectus, a failing

pertaining to something that is imperfect, or, as in an outdated term, to an individual who may be suffering from any disorder.

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Patient discussion about defective.

Q. Is it a birth defect in children? I know about the causes of autism. Is it a birth defect in children?

A. it's not an easy answer i'm afraid...there are congenital differences, but no "birth defect" that we can detect. there's a good pdf file that gives a full explanation about it...i think you'll find it useful:
http://209.85.129.132/search?q=cache:U7PHTfTAZhYJ:www.nichd.nih.gov/publications/pubs/upload/autism_overview_2005.pdf+http://www.nichd.nih.gov/publications/pubs/upload/autism_overview_2005.pdf&hl=iw&ct=clnk&cd=1&gl=il

Q. why does ADHD make kind of an hype to children? is it a nerve defect?

A. it's a complex interaction among genetic and environmental factors causing a disorder in the central nervous system. a study showed a delay in development of certain brain structures n the frontal cortex and temporal lobe, which are believed to be responsible for the ability to control and focus thinking.