What is considered a medical impairment? (i.e. Global developmental Delay in a child under the age of 5?)

SSA’s definition of disability differs from a solely medical definition in that it encompasses the child’s ability to function as compared with the functional abilities of a child of the same age who does not have impairments.

According to SSA, a medically determinable physical or mental impairment is an impairment that results from anatomical, physiological, or psychological abnormalities that can be shown by medically acceptable clinical and laboratory diagnostic techniques. A physical or mental impairment must be established by objective medical evidence from an acceptable medical source. 

SSA uses the Listing of Impairments to define the criteria for disability eligibility. The Listings are categorized by body system (i.e., cardiovascular, musculoskeletal, mental disorders). Developmental delays can be found in the following Listing: 112.14 Developmental disorders in infants and toddlers. The Listing can be found here: https://www.ssa.gov/disability/professionals/bluebook/112.00-MentalDisorders-Childhood.htm#112_14