Developmental disabilities is a broad term that encompasses both mental and physical conditions such as mental retardation, cerebral palsy, epilepsy, spina bifada, autism, Tourette syndrome, learning disabilities, and hearing and visual impairments. People with developmental disabilities may experience difficulty in such areas as self-care, language, mobility, learning, self-direction, independent living or self-sufficiency.

In a nutshell, the definition of developmental disability can be summarized as “a severe, chronic set of functional limitations which result from any physical and/or mental impairment” (Gollay, 1979, p.3) and which are readily apparent before age 22. A critical feature of the definition is the pervasiveness of the effect a developmental disability has on the person’s ability to function. The age of onset delineates two points: first, the disability occurs during the developmental period, making it difficult for the person to acquire necessary skills, and second, the difficulty must be demonstrated during the developmental period.

Thus, as Gollay (1979, p. 4) writes, “a developmental disability is a disability which has such a pervasive, cumulative and early impact on an individual that the person is likely to require long term care throughout life.”