implies, is diagnosed when an individual fa ils to meet expected developmental milestones
in several areas of intellectual functioning. The diagnosis is used for individuals who are
unable to undergo systematic assessments of intellectual functioning, including children
who are too young to participate in standardiz ed testing. Intellectual disability may result
from an acquired insult during the developm ental period from, for example, a severe head
injury, in which case a neurocognitive disorder also may be diagnosed.
The communication disorders include language disorder, speech sound disorder, so-
cial (pragmatic) communication  disorder, and childhood-onset fluency disorder (stutter-
ing). The first three disorders are characterize d by deficits in the development and use of
language, speech, and social communication, respectively. Childhood -onset fluency dis-
order is characterized by disturbances of the normal fluency an d motor production of
speech, including repetitive sounds or syllables, prolongation of consonants or vowel
sounds, broken words, blocking, or words pr oduced with an exce ss of physical tension.
Like other neurodevelopmental  disorders, communication di sorders begin early in life
and may produce lifelong functional impairments.
Autism spectrum disorder is characterized by  persistent deficits in social communica-
tion and social interaction across multiple cont exts, including deficits in social reciprocity,
nonverbal communicative behavior s used for social interaction, and skills in developing,
maintaining, and understandin g relationships. In addition  to the social communication
deficits, the diagnosis of autism spectrum disorder requires th e presence of restricted, re-
petitive patterns of behavior, interests, or activities. Because symptoms change with de-
velopment and may be masked by compensator y mechanisms, the diagnostic criteria may