What defines a developmental disability (DD)?

A developmental disability (DD) is specifically defined as a group of conditions that are characterized by impairments in physical, learning, language, or behavioral areas, and these conditions typically arise during the developmental period, which is defined as before the age of 22. This timeframe is critical because developmental disabilities often manifest in early childhood and can have lasting effects throughout an individual's life.

The defining aspect is that these disabilities must be present from a young age, as they impact the development of cognitive and physical functioning. This includes conditions such as intellectual disabilities, autism spectrum disorders, and other delays in development that are not solely caused by external factors after reaching adulthood.

In contrast, disabilities that arise during adulthood, acquired disabilities from injury, or transient conditions affecting learning do not fall under the definition of developmental disabilities, as they do not originate in the developmental period nor affect the overall trajectory of development from the outset.