52 Neurodevelopmental DisordersTABLE 2 Severity levels for autism spectrum disorder
Severity level Social communication Restricted, repetitive behaviors
Level 3 
“Requiring very substantial support”Severe deficits in verbal and nonverbal social com-
munication skills cause severe impairments in func-
tioning, very limited initiation of social 
interactions, and minimal response to social over-
tures from others. For example, a person with few 
words of intelligible speech who rarely initiates 
interaction and, when he or she does, makes 
unusual approaches to meet needs only and 
responds to only very direct social approaches.Inflexibility of behavior, extreme difficulty coping 
with change, or other restricted/repetitive behav-
iors markedly interfere with functioning in all 
spheres. Great distress/difficulty changing focus 
or action.
Level 2
“Requiring substantial support”Marked deficits in verbal and nonverbal social com-
munication skills; social  impairments apparent 
even with supports in place; limited initiation of 
social interactions; an d reduced or abnormal 
responses to social overtures from others. For 
example, a person who sp eaks simple sentences, 
whose interaction is limited to narrow special inter-
ests, and who has markedly odd nonverbal com-
munication.Inflexibility of behavior , difficulty coping with 
change, or other restricted/repetitive behaviors 
appear frequently enough to be obvious to the 
casual observer and inte rfere with functioning 
in a variety of contexts. Distress and/or difficulty 
changing focus or action.
Level 1 
“Requiring support”Without supports in place, deficits in social communi-
cation cause noticeable impairments.
Difficulty initiating social interactions, and clear 
examples of atypical or unsuccessful responses to