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Autism in Infant-hood

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 3-6 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 3 to 6 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 when 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. Self-generated experience, participation and exploration in the environment is what will shape and grow a child’s development. 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 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 while 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 a 3-4 month old infant into a sitting position, does their head lag back, indicating poor motor control? Do they find tummy time overly difficult and aversive? Are they late to meet their milestone of crawling, or have they developed an atypical method of moving around e.g. rolling, dragging? Do they reach out to grasp objects?

Social Engagement & 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 1-2 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 infants 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 and 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% of children with autism experience a regression of skills and this appears to be exclusive to autism. However, only around 29% of parents will notice a regression of skills unless the regression if very noticeable e.g. 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 behavioural 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 behavioural markers for autism, the infants who received early intervention before the age of 2, 90% of these toddlers made significant gains in their development throughout the first year of their early intervention. Toddlers who were between the age of 2-2.5, the