Why Are Girls Diagnosed with Autism Later in Ontario?
Direct answer
Research shows girls are often diagnosed with autism later than boys (Lockwood Estrin et al., 2021). This delay occurs because diagnostic tools were developed primarily from male presentations, some girls "mask" or camouflage social difficulties, and clinicians may not recognize autism in girls who do not display stereotypical behaviours. In Ontario, speaking up early for an assessment can matter.
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Why the Diagnostic Gap Exists
Three factors drive the later diagnosis of autism in girls: (1) Masking/camouflaging — girls are more likely to mimic social behaviours from peers, hiding their difficulties in structured settings like school. (2) Diagnostic bias — much of the research used mostly male samples, and common assessment tools were designed around how autism looks in boys. (3) Clinical expectations — many clinicians still associate autism with the "classic" male presentation (lining up toys, train obsessions) and may not recognize female-typical presentations (such as a strong wish to interact with others, or copying peers).
The result is that many girls are first given other diagnoses before autism is eventually identified.
Why Timing Matters
A wait spans childhood.
Early support can help autistic children develop skills. Age six is not a clinical cutoff, and support can be beneficial at any age. Illustrative arithmetic only: registration at age three plus a five-year wait reaches age eight. Age six is a reference marker, not a clinical cutoff. This is not a prediction of funding, service access or developmental outcomes.
Example: an illustrative child's journey through the Ontario Autism Program
An assumed five-year wait from registration at age 3 reaches age 8. This is an example, not a typical or predicted service date.
| Measure | Age range |
|---|---|
| Illustrative age reference | Birth to age 6 |
| Example wait using the OAC-reported minimum (registered age 3) | Age 3 to age 8 (5 years) |
| Age at the end of this illustrative wait | Past age 6 |
Toddler treatment study
Dawson et al. (2010) randomly assigned 48 autistic toddlers aged 18–30 months to the Early Start Denver Model (ESDM) or community intervention for two years. The ESDM group had greater improvements in cognitive and adaptive outcomes. This study compared treatments for toddlers; it did not compare intervention before versus after age six or establish a universal multiplier for gains.
Support across ages
NIH notes that treatment can help at any age. Support should reflect the person’s needs; a wait does not determine an individual child’s future outcomes.
Ontario does not publish an age-at-registration breakdown for registrations without an active Core Funding Agreement. This example does not describe the age distribution of that group.
SourceDawson et al. (2010) · NIH: autism and support across ages. The illustrative wait uses the community report: 5+ years for families registered in August 2021 (community-reported, Ontario Autism Coalition, July 2026). This is not a provincial average.
Frequently asked questions
Girls are often diagnosed later due to masking behaviours, diagnostic tools designed around male presentations, and clinical expectations biased toward male presentations.
Request a referral from your family doctor or pediatrician to a psychologist or developmental pediatrician experienced with autism in girls. Ask whether the clinician has experience assessing girls. Provide examples of difficulties at home (masking may hide difficulties at school).
Yes. Level 1 autism can be missed when masking makes social difficulties less visible. The effort of masking can cause exhaustion and anxiety, and autistic adults link it to burnout. Girls with Level 1 autism can still need support.
Write down the behaviours you notice and how they affect daily life. Ask your clinician to consider autism even if earlier screening did not raise a concern.
Sources
Lockwood Estrin et al. (2021), "Barriers to autism spectrum disorder diagnosis for young women and girls: a systematic review," Review Journal of Autism and Developmental Disorders, 8, 454-470
Checked
Loomes et al. (2017), "What is the male-to-female ratio in autism spectrum disorder?" Journal of the American Academy of Child & Adolescent Psychiatry
Checked
Public Health Agency of Canada — Autism spectrum disorder: Canadian Health Survey on Children and Youth, 2019
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Next step near you
Where to be assessed near you
- TorontoHolland Bloorview
- OttawaCHEO
- MississaugaErinoakKids (Mississauga Facility)
- BramptonErinoakKids (Brampton)
- North YorkHolland Bloorview (referral)
- ScarboroughSickKids (referral)
See every Ontario city we track
Assessment routes, local providers and school boards are tracked city by city. Pick the one closest to you.
Where the wait clock starts
A child's place in the Ontario Autism Program queue is set by the AccessOAP registration date. 71,263 children are registered and still waiting for core funding (MCCSS FOI via OAC · May 2026).
Next steps
Keep going with related guidance, tools, and evidence.
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Autism vs ADHD: Dual Diagnosis & Treatment in Ontario
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