Understanding Intellectual Disability (ID/IDD)

Plain-language guide to what an intellectual disability diagnosis in an assessment report means, for a parent or an adult.

If a report names an intellectual disability, sometimes written as ID or intellectual developmental disorder (IDD), it can stir up worry, relief, and a lot of questions at once. Whether you are a parent reading your child’s report or an adult reading your own, this guide explains what the diagnosis describes, how a professional reaches it, and what it does and does not mean. It describes the kind of support a person may need, not their worth or their potential. It explains a diagnosis your report already names. It does not diagnose, and only a qualified professional can determine whether it fits a particular person.

Quick answer. An intellectual disability involves meaningful differences in both reasoning and learning (intellectual functioning) and in everyday practical, social, and self-care skills (adaptive functioning), beginning in childhood. It is diagnosed by a qualified professional using cognitive and adaptive measures together with history, never from an IQ score alone, and it describes support needs rather than fixed limits.