Which statement best defines IDD?

• A. Disability that is only physical and limited to mobility
• B. Disability characterized by significant limitations in both intellectual functioning and adaptive behavior, with onset before age 22
• C. Disability defined by emotional instability
• D. Disability that arises after age 50 and is temporary

Answer: (B)

IDD is defined by substantial limits in both intellectual functioning (things like reasoning, learning, problem-solving) and adaptive behavior (the practical, social, and conceptual skills needed for daily life) that begin during the developmental period, before adulthood. The statement that describes these dual impairments with onset before age 22 best captures what IDD is. It isn’t about physical disability alone, nor about emotional instability, and it isn’t something that only occurs late in life or temporarily. This combination of cognitive and everyday-life challenges starting in development is what characterizes IDD.