Early identification of autism: signs, screening and diagnosis
Published July 21, 2026
Current guidance on early autism identification, using a 2015 review as historical context. Signs can prompt assessment, but no single sign or screening tool establishes a diagnosis.
Evidence status: current clinical guidance with historical research context.
Bottom line
Developmental differences associated with autism may be noticed during the first two years of life. An experienced professional can sometimes make a reliable diagnosis by age two, but development varies and uncertainty is more common in very young children. No single behaviour, screening score, laboratory test or imaging result establishes an autism diagnosis on its own.
Possible early differences
Families and professionals may notice differences in social communication, play, gestures, response to name, shared attention, movement patterns, interests, sensory responses, language or motor development. A loss of previously acquired language, social or motor skills should be discussed promptly with a healthcare professional. These observations can support a referral, but they can also have other explanations and are not a diagnosis by themselves.
Screening is not diagnosis
- Developmental surveillance combines family observations, developmental history and professional observation over time.
- Screening tools identify children who may benefit from further assessment; they do not confirm or rule out autism alone.
- A diagnostic assessment considers the child’s development and functioning across settings and may involve paediatrics, psychology, speech-language, occupational therapy or other professionals depending on the child’s needs and local pathway.
Support does not always need to wait
Canadian Paediatric Society guidance recommends referring children for appropriate needs-based supports, such as speech-language, occupational or early-development services, while a diagnostic assessment is pending. Families can ask a primary-care clinician about both the assessment pathway and supports for needs that are already present.
About the original 2015 paper
The original review, published in Psychiatriki, helped summarize research available at that time and has an English abstract on PubMed; the full article is in Modern Greek. Some terminology and claims in the abstract reflect older research and should not be read as current standalone guidance. The practical summary above is grounded in current CDC, Canadian Paediatric Society and NICE guidance.
Sources
- Kotsopoulos, 2015 review (PubMed)
- Canadian Paediatric Society: early detection
- NICE: recognition, referral and diagnosis
- CDC: screening and diagnosis
Source checked 6 August 2026. This page provides general information and does not diagnose autism or replace an individualized assessment.
Related support
- Find autism funding and support programs — Browse government and community programs by location.
- Compare autism services by city — Find assessment, therapy and support listings near you.
- Explore sensory-friendly places — Browse family-recommended places and reported accommodations.