Developmental disabilities are very severe disabilities that typically are lifelong in duration. The federal Developmental Disabilities Act defines a developmental disability as a severe, chronic disability that

• is attributable to a mental or physical impairment or a combination of mental or physical impairments;
• is manifested before the individual attains age 22;
• is likely to continue indefinitely;
• results in substantial functional limitations in three 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
• reflects the individual’s need for a combination and sequence of special, interdisciplinary, or generic services, supports, or other assistance that are of lifelong or extended duration and are individually planned and coordinated
• except that such term, when applied to infants and young children, means individuals from birth to age 9, inclusive, who have substantial developmental delay or specific congenital or acquired conditions with a high probability of resulting in developmental disabilities if services are not provided.