DD means developmental disability. A developmental disability is a mental or physical impairment that starts before age 22, continues indefinitely, and causes substantial difficulties in self-care, language, mobility, self-direction, independent living, learning and economic self-sufficiency. Specific examples include intellectual or cognitive disability, cerebral palsy, autism and various genetic and chromosomal conditions such as Down syndrome and Fragile X syndrome. Developmental disabilities can range in severity from mild to profound based on an individual's needs for supports. The incidence rate for developmental disabilities is 1-2 percent of the population in the Western world.