Intellectual Disability (Intellectual Developmental Disorder) 33
cians an opportunity to document factors that may have played a role in the etiology of the
disorder, as well as those that might affect the clinical course. Examples include genetic
disorders, such as fragile X syndrome, tuberous sclerosis, and Rett syndrome; medical con-
ditions such as epilepsy; and environmental fa ctors, including very low birth weight and
fetal alcohol exposure (even in the absence of stigmata of fetal alcohol syndrome).
Intellectual Disabilities
Intellectual Disability
 (Intellectual Developmental Disorder)
Diagnostic Criteria
Intellectual disability (intellectual development al disorder) is a disorder with onset during
the developmental period that includes both intellectual and adaptive functioning deficits
in conceptual, social, and practical domains. The following three criteria must be met:
A. Deficits in intellectual functions, such as reasoning, problem solving, planning, abstract
thinking, judgment, academic learning, and learning from experience, confirmed by
both clinical assessment and individualized, standardized intelligence testing.
B. Deficits in adaptive functioning that result in failure to meet developmental and socio-
cultural standards for personal independence and social responsibility. Without ongo-
ing support, the adaptive deficits limit functioning in one or more activities of daily life,
such as communication, social participation, and independent living, across multiple
environments, such as home, school, work, and community.
C. Onset of intellectual and adaptive deficits during the developmental period.
Note:  The diagnostic term intellectual disability  is the equivalent term for the ICD-11 diag-
nosis of intellectual developmental disorders.  Although the term intellectual disability  is
used throughout this manual, both terms are used in the title to clarify relationships with
other classification systems. Moreover, a federal statute in the United States (Public Law