Why are girls diagnosed with autism later?

A girl who works hard, behaves well and holds it together at school can go years without anyone asking whether she is autistic. A study published this year puts a number on the delay. Here is what it found, what it cannot tell you, and what a parent can do without waiting for a crisis.

What the 2026 study found

Researchers looked at electronic health records from 171,134 people in one large US health system, from 2016 to 2024. Females received an autism diagnosis a mean of 3.4 years later than males: at 15.7 years old, compared with 12.3 for males. Over those years, new diagnoses in males stayed steady or fell, while new diagnoses in females rose significantly after 2020 (Messias et al., JAMA Network Open, 2026).

What it cannot tell you

It is one health system, so it is not a measure of every country or clinic. It counted diagnoses recorded in health records; it did not test why females are diagnosed later, and it cannot say how many girls are never diagnosed. And it says nothing about your own child. A later average age is a pattern across thousands of people, not a verdict on one.

What other research points to

A 2026 systematic review pooled 26 studies published between 2015 and 2025 and found consistent diagnostic inequities: delayed diagnosis in girls, standard assessment tools that are less sensitive to presentations that are less outwardly disruptive, and social camouflaging (Muiño Tato, Revista de Neurología, 2026). Camouflaging means copying the people around you so that difficulties do not show. The review's authors conclude that diagnostic bias looks multifactorial and calls for approaches that are sensitive to gender.

That helps explain how a child can look fine at school and still be struggling. We cannot say that is true of any one girl, but it is a reason not to treat quiet and cooperative as proof that nothing is wrong. We describe the signs more fully in hidden signs of autism in girls, and what an exhausting stretch can look like in autistic burnout in children.

What to do if something feels off

• Write it down, with dates. What she finds hard and when: after school, in loud places, when plans change, with certain people. A dated list is something a teacher or doctor can use.
• Tell the school. Ask for a conversation with the class teacher and the school's learning-support team. Say what you see at home, and ask what they see.
• Talk to your child's doctor. Start with the family doctor or paediatrician and ask about an assessment. Ask what the waiting time is and what support is available while you wait.
• Do not wait for a crisis. A referral does not label a child. It starts a conversation, and the answer might be autism, ADHD, anxiety, something else or nothing.
• Look at the whole child. Autism, ADHD and dyslexia overlap often; see how ADHD, dyslexia and autism overlap.

What to bring, and what to say

Take the dated list, recent school reports or teacher comments, and a short note on what she is good at and enjoys, because an assessment looks at strengths as well as difficulties. Ask plainly: what is the process, how long is the wait, and what can the school put in place while we wait? If you are told it is "just anxiety" or "just shy", ask what would change that view and who to see if things get worse.

With your daughter, keep it low-key and about her experience, not a label: "I have noticed school takes a lot out of you, and I would like to understand why." Many parents find that a child who has been quietly coping is relieved to be asked.

If the answer turns out to be not autism, the work is not wasted. The list, the school conversation and the attention to what wears her out are useful for any child, and a late answer is better than none.

This post is information, not a diagnosis, and nothing here can tell you whether your child is autistic. Only a qualified clinician can do that.

References

• Messias, E., Casanova, E., Huang, R., Battula, S., Loftin, R., Walsh, M., & Lin, P.-I. (2026). Autism spectrum disorder incidence by age and sex in a US health care system, 2016 to 2024. JAMA Network Open. doi:10.1001/jamanetworkopen.2026.24561.
• Muiño Tato, A. (2026). Systematic review of autism in women: invisibilised profiles and gender bias. Revista de Neurología. doi:10.31083/rn49367.