Signs of Autism in a Toddler: Red Flags 12–24 Months

You’ve probably noticed that toddlers develop at wildly different speeds, but some differences deserve a closer look. Autism spectrum disorder (ASD) affects 1 in 36 children in the United States, and the first signs often emerge between 12 and 24 months (CDC). This guide walks you through the concrete red flags, the difference between autism and ADHD, and what to do if you’re worried — all grounded in the latest clinical guidelines.

First signs emerge: 12–24 months ·
U.S. prevalence (2025): 1 in 36 children ·
Median age of diagnosis: 4 years (CDC 2023) ·
Children showing signs by age 2: 80–90%

The table below summarizes key prevalence and diagnostic data.

How do I tell if my toddler has autism?

No single test gives an instant answer, but a combination of developmental milestones and observed behaviors can guide you. The NHS and CDC both emphasize three key domains: social communication, repetitive behaviors, and sensory sensitivities. Below is a milestone-based checklist.

Observable social communication differences

• By 12 months: little or no babbling, no response to name (CDC)
• By 16 months: very few or no words (Autism Speaks)
• Limited joint attention – not following your gaze or pointing to share interest (University of New Mexico)
• Lack of pretend play by 24 months

Repetitive behaviors and restricted interests

• Hand flapping, rocking, spinning, or pacing (NHS)
• Lining up toys instead of playing with them
• Strong insistence on routines or specific foods
• Unusual fascination with parts of objects (e.g., wheels, lights)

Checklist of milestones from 12 to 24 months

• 12 months: Should use gestures like waving, point at objects, say “mama”/“dada”
• 18 months: Should have at least 6 words, imitate actions, show interest in other children
• 24 months: Should use two-word phrases, point to show something interesting, copy adults (CDC)

Tracking these milestones gives parents a clear starting point for discussion with their pediatrician.

What are red flags for autism in a 2-year-old?

By 24 months, certain specific red flags become clearer. The CDC recommends autism-specific screening at 18 and 24 months, and the NHS warns that signs may be mistaken for other conditions.

Red flags at 18 months

• No single words
• No pretend play
• Does not show interest in other children
• Loss of any previously acquired language or social skills (Raising Children Network)

Red flags at 24 months

• No two-word phrases (even “go car”) (CDC)
• Limited or no eye contact
• Unusual posture or toe-walking
• Intense reactions to everyday sounds or textures

Regression or loss of skills

About 20–30% of autistic toddlers lose skills they once had – a phenomenon called regression. A child who said “mama” at 14 months but stops by 18 months is showing a major red flag. The Raising Children Network emphasizes that any loss of language or social engagement warrants an immediate screening.

The implication: parents should trust their instincts and seek evaluation if they see any skill loss, even if the child seems to be developing normally otherwise.

What are the top 5 signs of autism?

The DSM-5-TR diagnostic criteria cluster into two main areas: social communication deficits and repetitive, restricted behaviors. Here are the five most common signs parents observe in toddlers:

1. Social withdrawal

• Does not seek eye contact or responds to name inconsistently
• Prefers playing alone even when other children are present
• Does not bring objects to show you (lack of shared interest) (Autism Speaks)

2. Delayed speech or language regression

• No babbling by 12 months
• Fewer than 50 words by 24 months
• Loss of words such as “mama”, “dada”, or familiar object names

3. Repetitive movements (hand flapping, spinning)

• Rocking back and forth, flapping hands, or spinning in circles without apparent reason (NHS)
• These behaviors are often self-stimulatory and may increase when the child is excited or overwhelmed

4. Unusual sensory reactions

• Overreacts to loud noises (covers ears, cries) or underreacts to pain
• Licks or smells objects excessively
• Strong food texture aversions (refuses to eat anything that isn’t a specific consistency)

5. Lack of pretend play

• Instead of feeding a stuffed animal or driving a toy car, the child may line up objects or spin the car’s wheels
• Does not engage in simple back-and-forth games like peek-a-boo

Recognizing these five patterns helps parents differentiate typical toddler behavior from early autism markers.

Is my 2-year-old autistic or ADHD?

ADHD and autism share some behavioral surface features (hyperactivity, inattention), but the underlying drivers are different. About 30–50% of autistic children also have ADHD, so the conditions can coexist (CDC). The table below highlights the distinguishing clues.

The implication: If a toddler is highly active but also avoids eye contact and prefers spinning wheels to playing with you, the profile tilts toward autism. A child who is active but seeks interaction and talks early may lean toward ADHD. However, a formal evaluation by a developmental pediatrician is the only way to disentangle them.

What is borderline autism in a 2 year old?

“Borderline autism” isn’t a formal diagnosis in the DSM-5-TR. Parents and some clinicians use the term to describe a child who shows some autism-like traits but doesn’t meet the full diagnostic threshold. The older category PDD-NOS (Pervasive Developmental Disorder – Not Otherwise Specified) roughly captured this space.

Mild or atypical presentation

• Some social awareness but limited initiation
• Mild repetitive behaviors that don’t interfere with daily routine
• May speak in sentences but with odd prosody (robotic or sing-song)

Diagnostic challenges in borderline cases

• Many toddlers are diagnosed later because signs are subtle or mistaken for shyness or a speech delay (NHS)
• Comorbid conditions (ADHD, anxiety) can mask or mimic autism

Related terms: PDD-NOS, subthreshold autism

• Under DSM-IV, PDD-NOS was used for children who had some but not all autism features
• DSM-5 folded these cases into ASD with different severity levels
• Early intervention is still recommended even without a full diagnosis – the behaviors themselves are the target

For parents, the key takeaway is that subthreshold symptoms still warrant proactive support.

Do autistic 2 year olds cuddle?

Yes, many autistic toddlers enjoy cuddling and show affection. However, some may avoid touch due to sensory sensitivities, and others may cuddle on their own terms – for example, seeking deep pressure but pulling away from light touches.

Cuddling and affection patterns

• Some autistic children are intensely affectionate with caregivers but avoid strangers
• Others may initiate hugs only when they want comfort, not spontaneously
• Attachment style can vary; autism does not mean lack of love

Sensory processing differences

• Children with tactile hypersensitivity may find even soft touches painful (Golden Care Therapy)
• Deep pressure (tight hugs) can be calming, while light touch triggers defensiveness

Individual variation in autistic children

• Every autistic child is different – some seek constant physical contact, others avoid it entirely
• Cuddling behavior alone is not a reliable diagnostic sign; context matters

The pattern: sensory responses are highly individual – knowing your child’s baseline helps determine if avoidance is concerning.

Steps to take if you suspect autism

Acting early is the single most powerful thing a parent can do. The CDC recommends a step-by-step approach.

1. Track milestones. Use the CDC’s free Milestone Tracker app to note what your child does and doesn’t do at each age.
2. Talk to your pediatrician. Share your observations at the 18-month or 2-year well-child visit. Ask for a developmental screening.
3. Request an autism-specific screening. The M-CHAT (Modified Checklist for Autism in Toddlers) is a validated tool for children 16–30 months.
4. Seek a comprehensive evaluation. If screening suggests concern, ask for a referral to a developmental pediatrician, child psychologist, or an autism assessment team.
5. Start early intervention. Even before a formal diagnosis, speech therapy, occupational therapy, and behavioral support (e.g., ABA) can begin. Many services are available through your state’s early intervention program (CDC).

Following these steps gives families a clear path forward and maximizes the window for effective support.

Timeline: What autism red flags look like at each age

Developmental warning signs change as a child grows. Here’s a month-by-month guide:

This timeline helps parents know what to look for at each checkpoint and when to raise concerns with a doctor.

What’s confirmed and what’s still unclear

Understanding the limits of current knowledge helps families approach screening with realistic expectations.

Expert perspectives

“Developmental monitoring and screening at 9, 18, and 30 months, with autism-specific screening at 18 and 24 months, are critical for early identification.”

— CDC (U.S. public health agency)

“Signs of autism can be seen in very young children, but some children are diagnosed later because signs are missed or mistaken for something else.”

— NHS (U.K. national health service)

“Loss of language or social skills – regression – affects about 20-30% of autistic children and is a major red flag.”

— Raising Children Network (Australian parenting resource)

“Many autistic children do cuddle and show affection; some may avoid touch due to sensory sensitivities.”

— Golden Care Therapy (child therapy provider)

What this means for your family

For parents of a toddler showing early signs, the message is clear: act early, not later. A screening at 18 months could be the difference between early intervention and years of missed support. The CDC’s Learn the Signs program gives you free tools. Trust your gut – you know your child best. If something feels off, push for answers.

For parents who notice red flags before 12 months, it is helpful to also review the early signs of autism in babies, which often include reduced eye contact and delayed babbling, as detailed in early signs of autism in babies.

Frequently asked questions

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• High Blood Pressure Treatment – medical treatment overview

These articles provide additional context on managing overall family health alongside autism care.