Introduction
One of the most common reasons parents seek professional advice during the toddler years is concern about speech and language development. A child may not be talking as expected, may use only a few words, or may appear not to understand what is being said to them.
At ages two and three, it can sometimes be difficult to distinguish between a language delay, a developmental language disorder (DLD), and Autism Spectrum Disorder (ASD) because all three can affect communication. However, while they may look similar on the surface, they have different underlying causes and require different assessment approaches. Research has also shown that many young children with autism initially present with concerns about language development, which can sometimes delay recognition of autism.
What is a Language Delay?
A language delay occurs when a child’s speech and language skills develop more slowly than expected for their age.
A child with a language delay may:
- Say fewer words than expected.
- Start combining words later than peers.
- Have difficulty understanding language.
- Struggle to express their needs verbally.
Importantly, a language delay describes a developmental pattern rather than a diagnosis. Some children with delayed language catch up with their peers over time, while others go on to meet criteria for a developmental language disorder or another neurodevelopmental condition.
What is Developmental Language Disorder (DLD)?
Developmental Language Disorder is a neurodevelopmental condition characterised by persistent difficulties with understanding and/or using spoken language that cannot be explained by hearing loss, intellectual disability, autism, or another medical condition.
DSM-5 Criteria for Language Disorder:
The DSM-5 classifies Language Disorder within the Communication Disorders category.
The diagnostic criteria include:
- Persistent difficulties acquiring and using language across spoken, written, sign, or other forms of communication.
- Reduced vocabulary.
- Difficulties producing sentences.
- Difficulties using language to communicate effectively.
- Language abilities that are substantially below what would be expected for age.
- Difficulties that impact educational, social, or occupational functioning.
- Symptoms beginning during the developmental period.
- Difficulties not better explained by intellectual disability, autism, hearing impairment, or another condition.
In young children, this may present as delayed first words, difficulty combining words into sentences, or challenges understanding spoken language.
What is Autism Spectrum Disorder?
Autism is a neurodevelopmental condition that affects social communication, social interaction, behaviour, interests, and sensory processing.
Although many autistic children experience language delays, autism is not defined by speech delay alone. Under DSM-5 criteria, language difficulties must occur alongside broader social communication differences and restricted or repetitive behaviours.
DSM-5 Criteria for Autism Spectrum Disorder:
To receive an autism diagnosis, a child must meet all of the following social communication criteria:
A. Persistent differences in social communication and social interaction
- Deficits in social-emotional reciprocity
- Reduced sharing of interests or emotions.
- Limited back-and-forth interaction.
- Difficulties initiating or responding to interactions.
- Deficits in non-verbal communication
- Differences in eye contact.
- Reduced use or understanding of gestures.
- Difficulties interpreting facial expressions.
- Deficits in developing and understanding relationships
- Difficulties engaging with peers.
- Limited social play.
- Reduced interest in social interaction.
B. Restricted and repetitive patterns of behaviour
At least two of the following must be present:
- Repetitive movements or speech.
- Strong preference for routines.
- Highly focused interests.
- Sensory differences.
Symptoms must be present from early childhood and cause a significant impact on everyday functioning.
Why Are These Conditions Sometimes Confused?
The main reason is that speech delay is often one of the earliest signs noticed by parents.
Research comparing children with autism and developmental language delay found that both groups demonstrate communication difficulties and both may show elevated levels of autistic-like behaviours compared to typically developing children.
As a result, it is not always possible to distinguish between the conditions simply by counting words or measuring language ability.
The Key Difference: Social Communication
The most important distinction is whether the child’s difficulties are limited to language or affect broader social communication.
Children with Language Delay or DLD Often:
- Show strong interest in people.
- Seek out social interaction.
- Use eye contact naturally.
- Point to share interests.
- Bring toys to show parents.
- Respond consistently to their name.
- Enjoy interactive games such as peek-a-boo.
- Attempt to communicate even when words are limited.
Whereas Children with Autism May Show:
- Reduced response to their name.
- Limited joint attention.
- Less frequent pointing to share interests.
- Reduced eye contact.
- Differences in social reciprocity.
- Limited imitation skills.
- Reduced interest in peer interaction.
- Repetitive behaviours or sensory differences.
A child with a language disorder generally wants to communicate but struggles with language. An autistic child may have differences in how they communicate, engage socially, and experience the world more broadly.
Joint Attention: An Important Early Sign
A useful concept for recognising autism in the context of language delay is joint attention.
Joint attention refers to the ability to share attention with another person around an object or event.
Examples include:
- Looking where a parent points.
- Pointing to show something interesting.
- Looking between an object and another person.
Many autistic toddlers have delays in joint attention development, whereas children with language delay alone usually develop these social communication skills even when spoken language is limited.
Why Autism is Often Dismissed in 2- and 3-Year-Olds
Many parents report being told:
- “He’s just a late talker.”
- “Boys talk later.”
- “Let’s wait and see.”
- “She’ll catch up.”
While some children do naturally catch up, autism may be overlooked when professionals focus solely on speech and language development.
There are several reasons this happens:
Language Delay is More Obvious Than Social Differences:
Parents often notice missing words before they notice difficulties with joint attention, gesture use, or social reciprocity.
Because speech delay is so visible, it can become the primary focus of concern.
Research shows that delayed language development is often one of the first reasons young children with autism are referred for assessment.
Autism Presents Differently in Different Children:
Not every autistic toddler presents in the same way.
Some autistic children:
- Smile frequently.
- Enjoy cuddles.
- Show affection.
- Use some words.
- Make occasional eye contact.
This variability can lead people to incorrectly assume a child cannot be autistic.
Professionals May Want More Developmental Information:
Autism assessments rely on identifying patterns across multiple areas of development.
Some professionals prefer to monitor development over time before reaching firm conclusions, particularly in children whose presentation is complex or subtle. However, monitoring development should not mean delaying referral when concerns are significant.
When Should Parents Consider an Autism Assessment?
A language delay alone does not indicate autism. However, parents should consider seeking an autism assessment if language difficulties occur alongside:
- Poor response to name.
- Limited eye contact.
- Reduced use of gestures.
- Delayed joint attention.
- Limited interest in peers.
- Repetitive behaviours.
- Strong need for routines.
- Sensory sensitivities.
- Regression in language or social skills.
- Difficulties engaging in pretend play.
The combination of communication differences and broader social, behavioural, or sensory characteristics is often more informative than speech development alone.
Conclusion
Language delay, developmental language disorder, and autism can appear similar during the toddler years because all can affect communication. However, autism involves broader differences in social communication, social interaction, behaviour, and sensory processing that go beyond language skills alone.
For 2- and 3-year-olds, the most important question is often not simply“How many words does my child use?” but“How does my child communicate, connect, and interact with other people?”
When concerns extend beyond speech and language to include social interaction, joint attention, play skills, sensory differences, or repetitive behaviours, a comprehensive autism assessment may help families better understand their child’s developmental profile and support needs.
References
American Psychiatric Association (2022) Diagnostic and Statistical Manual of Mental Disorders: DSM-5-TR. 5th edn., text revision. Washington, DC: American Psychiatric Publishing.
Özyurt, G. and Dinsever Eliküçük, Ç. (2018) ‘Comparison of language features, autism spectrum symptoms in children diagnosed with autism spectrum disorder, developmental language delay, and healthy controls’, Noro Psikiyatri Arsivi, 55(3), pp. 205–210. Available at:
Wiggins, L.D., Rice, C.E., Barger, B., Soke, G.N., Lee, L.C., Moody, E., Edmondson-Pretzel, R. and Levy, S.E. (2019) ‘DSM-5 criteria for autism spectrum disorder maximises diagnostic sensitivity and specificity in preschool children’, Social Psychiatry and Psychiatric Epidemiology, 54(6), pp. 693–701
