Autism in infanthood

Child Behavior

Sarah Murray is a Paediatric Board Certified Behaviour Analyst (BCBA). Her practice is based in county Cork but she works online supporting many families. Sarah specialises in early intervention for infants and young children, with almost a decade of experience working alongside families of children with developmental delays, autism, and intellectual disability. A child behavioural consultant, Sarah helps families and schools to address challenging behaviour in a positive manner using evidence-based intervention strategies.

Paediatric Behaviour Analyst Sarah Murray looks at the research and what it tells us about autism in infants and toddlers including the crucial aspect of time in diagnosis and early intervention

Have you ever had concerns about your infant or toddler’s development? Have you noticed that they are missing some key milestones or perhaps they are developing atypical behaviours? Has your toddler lost skills that they once had? 

Research now shows us that early behavioural markers of autism begin to emerge between three to six months of age, becomingly readily apparent by the age of 12 months. At 18-months-of-age, an infant can be reliably diagnosed as meeting the criteria for an autism diagnosis. However, wait times for an assessment across Ireland mean that children can be anywhere from three- to six-years-of-age and beyond before they receive their assessment and diagnosis.

From the age of birth to 24 months, an infant’s brain undergoes rapid development, the most rapid that any of us will experience in a lifetime. During this period, an infant’s brain density will double in size and they will develop 700 neural connections every second. It is during this period that skills are only beginning to emerge as their neural circuitry is laid down. Connections are strengthened as they participate in their environment, whilst other non-essential connections are pruned. It is at this crucial point in development, as social, cognitive and language delays become apparent, that pre-emptive intervention (intervention prior to the age of 18/24 months) can transform a child’s developmental trajectory. 

It is important for caregivers to know that they do not have to wait for a diagnosis for their infant or toddler in order to receive therapeutic input. Infants who are presenting with delayed, absent or atypical behavioural markers can and should receive early intervention at the first signs of developmental concerns. Early intervention seeks to realign the trajectory of a child’s development by mapping onto what we know about the many typical and expected developmental milestones and guiding the infant’s development in order to ensure that these milestones are attained. Many milestones during this period are crucial for further learning and development. For example, if an infant is not attending to people in their environment, then they could fail to grasp the shared fun and enjoyment that can come through engaging with others, or they might not learn the communicative opportunities that are had when interacting with caregivers. 

You might ask yourself, what are these early behavioural indicators of autism in infants and young toddlers? There are a few, but it is important to be mindful of two things; not all of these markers will be applicable to all the children who later go on to receive a diagnosis of autism. Some children may show many of these behavioural signs, others may not. It is also very important to note that a typically developing infant may show one or two of these markers, but when you are noticing a cluster of these markers, it is this cluster that can be indicative of a later diagnosis of autism. 

Motor Delays

The earliest known indicator for a later diagnosis of autism are motor delays, poor or weak motor ability, or atypical motor development. For example, when you pull an infant into a sitting position, does their head lag back, indicating poor motor control? Are they late to meet their milestone of crawling or have they developed an atypical method of moving around, for example rolling, dragging?

Social Engagement and Communication

Another key marker identified is poor or absent social engagement. Parents and clinicians report noticing a lack of shared social interest, which is called joint attention. Infants might have low affect meaning that they can appear ‘expressionless’, and may not engage in social smiling. Social smiling begins to emerge at the age of three to four months, where a baby will smile back at a smiling caregiver. Infants can present with lack of eye contact and an absence of looking at people in general or attending to their voice. Infants and toddlers who do not respond when they hear their name called is the most commonly reported behavioural marker for a later diagnosis of autism. Some may notice that their infant has a low anticipatory response. An example of this is when a caregiver say’s “ready, steady” and pauses, typically children will squeal in delight at the anticipation of what is to come, but this kind of response can be absent in infants who later go on to receive a diagnosis of autism.

Gesturing to people such as waving or pointing may be limited or absent, as can responding to a caregivers gestural cues such as responding to what a caregiver might point to in order to bring this to their infant’s attention. This ties closely with poor visual tracking, reaching and grasping of items.

Infants who later go on to receive a diagnosis of autism can show preference for objects over people and can engage in repetitive inspecting, turning of objects as opposed to engaging in cause and effect with them. Poor imitation skills and lack of babbling, cooing and spoken words are also key indicators of a social and communication delay.


One very interesting piece of research has discovered that up to 88 per cent of children with autism experience a regression of skills and this appears to be exclusive to autism. However, only around 29 per cent of parents will notice a regression of skills unless the regression if very noticeable, for example a loss of spoken words.

If you have noticed some behavioural markers with your infant, you may have been told by some that each child develops at their own rate, which granted is true to an extent, but be mindful of clusters of markers. Sometimes parents might be told to ‘wait and see’. There is a very interesting study that asks the question, how much does a month matter in terms of early intervention. What does it cost an infant to wait and see? From a sample of infants who were screened as presenting with markers for autism, the infants who received early intervention before the age of two, 90 per cent of these toddlers made significant gains in their development throughout the first year of their early intervention. In toddlers who were between the age of two to two-and-a-half, these significant gains dropped to 70 per cent in their first year of early intervention.In toddlers aged between two-and-a-half to three, their significant gains made during the first year of early intervention dropped to 30 per cent. What I would like to stress to caregivers who are reading this, is that it does not mean that your child cannot learn these skills. What this study points out is the crucial aspect of time. The earlier intervention begins, the faster and more readily skill acquisition occurs, because intervention prior to the age of two capitalises on what we know and understand about neuroplasticity in the brain of a 0-24-month-old child.

If you are having concerns about your infant or toddlers development, please feel free to reach out at: 

WCP Staff

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