Autism is not caused by one thing, and researchers cannot yet predict which children will be autistic. What has changed in the last few years is that brain imaging can now detect differences in infancy, months before the traits that lead to a diagnosis are visible to parents or clinicians.
Some of the most important work on this was led from North Carolina. This guide covers what the research has established, what remains hypothesis, how common autism is now, and what any of it means for a family waiting on an evaluation.
If your child is young and you have concerns, early intervention does not require a confirmed diagnosis to begin.
How Common Autism Is Now
The CDC’s Autism and Developmental Disabilities Monitoring Network estimates that 1 in 31 eight-year-old children, or 3.2%, were identified with autism spectrum disorder in its 2022 surveillance year, published in April 2025.
That figure has moved substantially. Older articles still quote 1 in 54, which was the 2016 surveillance year. If a source you are reading uses that number, it is roughly a decade behind.
Autism was identified in about 3.4 boys for every girl among eight-year-olds. Researchers continue to debate how much of that gap is biological and how much reflects girls being identified later or missed entirely.
Rising identification rates are not straightforward evidence of rising autism. Broader diagnostic criteria, better screening, and improved access to evaluation all increase the count. Our post on autism statistics in North Carolina covers the state picture.
What Brain Imaging Has Found
The clearest recent finding concerns the amygdala, a brain structure involved in processing emotion and social information.
Researchers with the Infant Brain Imaging Study network, a consortium of ten universities across the US and Canada, scanned infants repeatedly through their first two years. They found that in infants later diagnosed with autism, the amygdala grows unusually fast, and that the overgrowth begins between 6 and 12 months of age, before autism traits are apparent. Infants whose amygdala grew fastest in the first year showed greater social differences at age two.
The study was published in the American Journal of Psychiatry in March 2022, and its first author, Mark Shen, is at UNC Chapel Hill.
Two details make the finding more credible than a single correlation. The pattern was specific: infants with fragile X syndrome, a different neurodevelopmental condition, showed no amygdala growth differences. And the overgrowth preceded the behavioural signs rather than following them.
One thing worth separating out. Shen has suggested that infants with early sensory processing difficulties may experience something like ongoing stress, which could drive the amygdala growth. That is a reasonable hypothesis about mechanism, and it is not what the study demonstrated. Plenty of articles report it as established. It is not.
What this does not mean is that brain scans can now diagnose autism. This is research-grade imaging on infants already known to be at elevated likelihood, and nothing here is available as a clinical test.
Genetics and Environment
Autism runs strongly in families, and twin and family studies consistently point to a substantial genetic contribution. But there is no single autism gene. Many genetic variants each contribute a small amount, and different children arrive at autism through different combinations.
Prenatal and early environmental factors are an active research area, including maternal infection and immune activation during pregnancy. The honest summary is that associations have been observed, mechanisms are not established, and none of it supports a claim that a particular exposure causes autism in a particular child.
What families often want to know is whether something they did caused it. Nothing in the current evidence supports that, and parenting is not among the factors under investigation.
Why the Timing Matters
The reason infant brain research gets attention is not that it changes a diagnosis. It is that it adds weight to something already well supported: the developmental window in the first few years is when intervention has the most to work with.
The practical implication for parents is simpler than the science. You do not need to wait for certainty. In North Carolina, a child can be referred for early intervention services on the basis of developmental concerns, before any autism diagnosis is confirmed, and evaluation waits are often long enough that waiting for one costs real time.
Our guide to early intervention for autism covers how referral works and what services involve.
Early Signs Parents Notice
Signs vary a great deal between children, and the ones below are reasons to seek an evaluation rather than indicators of autism on their own:
- Not responding to their name by around 12 months
- Delayed speech or loss of words previously used
- Limited eye contact or difficulty following a point
- Little pretend play
- Repetitive movements or intense focused interests
- Strong reactions to sound, texture, light, or taste
A child showing several of these deserves an evaluation. A child showing one may simply be developing at their own pace. Only a qualified evaluator can make that distinction, and our post on signs of mild autism in toddlers covers the more easily missed presentations.
What the Evidence Supports
Behavioural intervention has the strongest evidence base for supporting development in autistic children. Applied behavior analysis breaks skills into teachable steps and uses reinforcement to build communication, social and daily living skills, with programmes individualised to the child.
In center-based ABA therapy, a child works with a team in a setting built for it, which suits some children better than home-based sessions. Families we work with often use a combination, and what works usually becomes clear within the first months rather than being predictable in advance.
One area deserves a correction, because it circulates widely. Specialised diets are often recommended for autism, particularly gluten-free and casein-free diets and various supplements. A systematic review published in Pediatrics, the journal of the American Academy of Pediatrics, concluded that there is little evidence to support the use of nutritional supplements or dietary therapies for children with autism. Gluten-free casein-free diets were rated as having insufficient evidence; omega-3 supplements showed low-strength evidence of no effect on challenging behaviours.
This matters beyond wasted effort. Many autistic children already eat a narrow range of foods, and removing more without clinical supervision risks nutritional gaps. If you want to try a dietary change, do it with your child’s pediatrician or a dietitian rather than alone.
Conclusion
Research shows that autism develops through a complex combination of genetic and biological factors, with differences in brain development beginning long before noticeable signs appear. While scientists continue to study how autism develops, there is still no single known cause or reliable way to predict which children will be autistic.
For parents, the most important step is recognizing developmental concerns early and seeking professional guidance. Signs such as delayed speech, limited social interaction, or repetitive behaviors may indicate the need for an evaluation. Early intervention can help children build communication, social, and daily living skills without waiting for a confirmed autism diagnosis.
What This Means for Your Family
The research picture is genuinely moving. Autism begins developing well before anyone can see it. The brain differences are measurable in infancy, and the genetic contribution is substantial and complex. None of that gives a parent a test, a cause, or a prediction.
What it does support is acting on concerns early rather than waiting for certainty, being sceptical of interventions that promise more than the evidence shows, and getting a proper evaluation from someone qualified to do one.
Connect n Care ABA works with families across North Carolina through early intervention, center-based ABA therapy, and in-home ABA therapy, including children who are still awaiting a diagnosis.
To talk through what would help your child, contact our team.
SOURCES:
- https://publichealth.jhu.edu/2025/new-cdc-report-shows-increase-in-autism-in-2022-with-notable-shifts-in-race-ethnicity-and-sex
- https://newsroom.uw.edu/news-releases/brain-overgrowth-seen-babies-who-later-develop-autism
- https://www.asatonline.org/wp-content/uploads/asatdocuments/AAP-2017-Sathe-et-al-Pediatrics-Nutritional-and-Dietary-Interventions-for-Autism.pdf
- https://www.cdc.gov/autism/signs-symptoms/index.html
- https://www.cdc.gov/autism/data-research/index.html
- https://www.iacc.hhs.gov/publications/summary-of-advances/2012/question5.shtml
