Children less than two years old

Communication

• Limited functional communication or regression/loss of language skills*
• Limited understanding and/or use of specific gestures
• No babbling/gesturing (pointing, waving bye-bye) at 12 months
• <25 words/approximations at 18 months
• <50 words/approximations at 24 months OR no 2-word combinations at 24 months

Socialization

• Lack of joint attention skills at 3-6 months*
• Limited social response and/or engagement with another person
• No social smile/gaze (focus on another portion of communication partner's face)
• Failed Modified Checklist for Autism in Toddlers (M-CHAT)

Behavior

• Rigid behaviors for routines, (i.e., bedtime)*
• Repetitive movement of objects or self, aggression or self-injurious behavior*
• Irritable, inconsolable or soothes only by motion
• Limp/rigid when held
• Difficulty sleeping
• Difficulty progressing to table food

Motor/Sensory

• Inactive or extremely active child (limp/floppy or constantly moving)
• Delay of motor milestones
• Unusual sensitivity to environmental stimuli (tactile, auditory or visual)
• Resistive to being cuddled

Children two years old and older

Communication

• Cannot consistently express needs/desires*
• Any regression or loss of speech/language skills at any age*
• Limited consistency of functional communication and conversation skills
• Engages others only to meet a particular need (i.e., fix a toy)

Socialization

• Engages others only to meet a particular need*
• Impairment in understanding social interaction or environmental safety rules
• Limited nonverbal communication skills (facial expressions, gestures)
• Often plays alone or has difficulty "getting along with others"
• Appears to relate better to adults than peers

Behavior

• Repetitive movements of self, objects or motor activities*
• Rigid behaviors for routines - insistence on certain routines or changes in routines*
• Aggression or self-injurious behavior
• Focused and repetitive interests limit creative play
• Picky eater

Motor/Sensory

• Fine motor difficulties
• Delay of motor milestones
• High pain tolerance
• Overly sensitive to everyday stimuli (i.e., loud sounds, sun/lights, tooth brushing, haircuts and nail clipping, bothered by tags in clothes)
• Not bothered by extreme cold

* Presence of more than one of these indicators greatly increases risk of ASD diagnosis.