Direct answer
Autistic girls are diagnosed an average of 1.5 years later than boys according to a 2017 study by Loomes, Hull, and Mandy, and many are missed entirely. The male-to-female diagnosis ratio is approximately 3:1 to 4:1, but research suggests the true prevalence gap is smaller. Girls are more likely to mask (camouflage) autistic traits by imitating social behaviour, leading to missed or delayed diagnosis. Ontario families should seek assessors experienced in female autism presentations.
Start with the short answer, then reveal deeper context where helpful.
Autism diagnostic criteria and screening tools were developed primarily from research on boys. Autistic girls often present differently: they may have more social motivation, more developed language, and restricted interests that appear typical (animals, reading, art). They are more likely to camouflage or "mask" their difficulties by observing and imitating peers' social behaviour.
When seeking an autism assessment for a girl or woman in Ontario, look for clinicians who specifically state experience with female autism presentations. Ask whether they use tools validated for both sexes and whether they consider masking in their assessment. The Camouflaging Autistic Traits Questionnaire (CAT-Q) can supplement standard diagnostic tools.
Autism diagnostic criteria and screening tools were developed primarily from research on boys. Autistic girls often present differently: they may have more social motivation, more developed language, and restricted interests that appear typical (animals, reading, art). They are more likely to camouflage or "mask" their difficulties by observing and imitating peers' social behaviour.
Masking is exhausting and has mental health consequences. Many girls and women receive diagnoses of anxiety, depression, anorexia, or borderline personality disorder before autism is recognized. Teachers and clinicians may dismiss concerns because the girl "seems social" or "has friends." Dworzynski et al. (2012) found that girls needed more severe behavioural problems than boys to receive a diagnosis.
When seeking an autism assessment for a girl or woman in Ontario, look for clinicians who specifically state experience with female autism presentations. Ask whether they use tools validated for both sexes and whether they consider masking in their assessment. The Camouflaging Autistic Traits Questionnaire (CAT-Q) can supplement standard diagnostic tools.
In Ontario, clinicians at CAMH, Holland Bloorview, and several private practices specialize in assessing girls and women. Costs and wait times are similar to general autism assessments: $2,500–$4,000 private, or 12-24 months through public pathways. Online communities like the Ontario Women and Nonbinary Autism Network can recommend knowledgeable assessors.
Research
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
Research
Dworzynski et al. (2012), "How Different Are Girls and Boys Above and Below the Diagnostic Threshold for ASD?" JADD, 42, 1219-1229
Girls are diagnosed with autism an average of 1.5 years later than boys. Learn about masking, diagnostic bias, and how to advocate for assessment.
In Ontario, autism can be diagnosed by psychologists, developmental pediatricians, psychiatrists, and some pediatricians. Learn the pathways and costs.
Adult autism diagnosis in Ontario: CAMH adult assessment, private costs, OHIP coverage, and why many people are diagnosed after age 30.
Commitment to Accuracy: Our data is verified against official government reports (FAO, MCCSS), peer-reviewed scientific literature, and accessible public records. Last updated: March 24, 2026.
Written by Spencer Carroll
Founder & Autism Advocate