Autism Diagnosis in Girls: Understanding Masking and Missed Diagnosis
Direct answer
Autistic girls are often diagnosed later than boys, though study results vary (Lockwood Estrin et al., 2021), and many are missed entirely. Boys are diagnosed with autism more often than girls, though research suggests the true prevalence gap between the sexes is smaller than the diagnosed gap (Loomes et al., 2017). Girls are more likely to mask (camouflage) autistic traits by imitating social behaviour, leading to missed or delayed diagnosis. Ontario families can ask an assessor about their experience assessing girls and women.
Why Timing Matters
The wait outlasts the window.
Clinical research (American Academy of Pediatrics; Hyman et al., Pediatrics 2020) identifies birth to age six as the peak neuroplasticity window for autism intervention. Ontario's reported minimum wait is 5+ years for families registered in August 2021 (community-reported, Ontario Autism Coalition, July 2026).
Example: an illustrative child's journey through the Ontario Autism Program
Registered at age 3. Services begin at age 8, after 5+ years for families registered in August 2021 (community-reported, Ontario Autism Coalition, July 2026), most of it inside the intervention window.
| Measure | Age range |
|---|---|
| Early-intervention window (AAP) | Birth to age 6 |
| Example wait using the OAC-reported minimum (registered age 3) | Age 3 to age 8 (5 years) |
| Age when services begin in this example | Past age 6 |
✓ Intervention before 6
Research shows 2× greater gains in cognitive and adaptive functioning. Some children lose their diagnosis entirely. The brain's plasticity makes early therapy dramatically more effective.
◌ Intervention after 6
Reduced neuroplasticity means slower progress, higher lifetime costs, and poorer outcomes. Every year of delay narrows the range of achievable milestones. Ontario's waitlist guarantees this for most families.
Of the 71,263 children on the unfunded backlog, the majority were registered between ages 2 and 4. At the current pace, most will age past 6 before receiving any core funding , missing the window that the American Academy of Pediatrics and every major autism research body identifies as critical.
SourceAmerican Academy of Pediatrics (Hyman et al., Pediatrics 2020) · Ontario MCCSS OAP data via FOI · Wait: 5+ years for families registered in August 2021 (community-reported, Ontario Autism Coalition, July 2026).
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Why Girls Are Missed
- Autism diagnostic criteria and screening tools were developed primarily from research on boys. Autistic girls often present differently: they may have more social motivation and interests that look similar to their peers' interests. They are more likely to camouflage or "mask" their difficulties by observing and imitating peers' social behaviour.
- The effort of masking can cause exhaustion and anxiety, and autistic adults link it to burnout. Many girls and women receive other diagnoses first, such as anxiety, anorexia, or borderline personality disorder, before autism is recognized. Some clinicians and others may doubt parents' concerns because they see autism as a "boy's disorder." Dworzynski et al. (2012) found that, without extra intellectual or behavioural problems, girls were less likely than boys to meet diagnostic criteria at the same level of autistic traits.
Finding the Right Assessor in Ontario
- When seeking an autism assessment for a girl or woman in Ontario, ask the clinician about their experience assessing girls and women, and whether they consider masking in their assessment. The Camouflaging Autistic Traits Questionnaire (CAT-Q) is a self-report measure of masking for adults (Hull et al., 2019).
- In Ontario, CAMH assesses adults for autism (18 and older), and Holland Bloorview assesses children and youth under 18 in Toronto. Costs and wait times vary by provider and pathway — contact assessors directly for current pricing and availability.
Frequently asked questions
Research points to several barriers: studies and assessment tools built mostly around boys, camouflaging of autistic traits, and other diagnoses being given first (Lockwood Estrin et al., 2021).
Masking (or camouflaging) means hiding or working around autistic traits in social situations (Hull et al., 2017). Research with autistic adults links masking to exhaustion and anxiety, and autistic adults link it to burnout.
Ask prospective assessors directly about their experience assessing girls and women, and whether they consider masking. Holland Bloorview (children and youth under 18), CAMH (adults), and the College of Psychologists and Behaviour Analysts of Ontario public register can help you find assessors.
Sources
Loomes, Hull & Mandy (2017), "What Is the Male-to-Female Ratio in ASD?" Journal of the American Academy of Child and Adolescent Psychiatry, 56(6), 466-474
Checked
Dworzynski et al.
Dworzynski et al. (2012), "How different are girls and boys above and below the diagnostic threshold for autism spectrum disorders?" Journal of the American Academy of Child and Adolescent Psychiatry, 51(8), 788-797
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(4), 454-470
Checked
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.
Related questions
Why Are Girls Diagnosed with Autism Later in Ontario?
Girls are often diagnosed with autism later than boys. Learn about masking, diagnostic bias, and how to advocate for assessment.
Who Can Diagnose Autism in Ontario?
In Ontario, trained doctors, psychologists, psychological associates and nurse practitioners can diagnose autism. Learn the pathways and costs.
How Adults Get Referred for an Autism Assessment in Ontario
How an adult gets referred for autism assessment in Ontario: the CAMH route, what a family doctor can and cannot refer for, and where to go when no public pathway exists.
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