Intellectual disability begins in childhood. People with intellectual disability have limits in their mental functioning seen in below-average intelligence (IQ) tests and in their ability to communicate, socialize, and take care of their everyday needs. The degree of disability can vary from person to person. It can be categorized as mild, moderate, severe, or profound.

Several hundred causes of intellectual disability have been discovered, but many are still unknown. The most common ones are:

Double-stranded piece of DNA
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Head Injury in Child
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