20 ILCS 1705/48.1

For current planning purposes, developmental disabilities is defined as a severe, chronic disability of a person which: (a) is attributable to a mental or physical impairment or combination of mental and physical impairments; (b) is manifested before the person attains age 22; (c) is likely to continue indefinitely; (d) results in substantial functional limitations in 3 or more of the following areas of major life activity: self care, receptive and expressive language, learning, mobility, self-direction, capacity for independent living and economic self-sufficiency; and (e) reflects the person's need for a combination and sequence of special interdisciplinary or generic care, treatment or other services which are of lifelong or extended duration and are individually planned and coordinated.