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Autism and sex/gender in research

Who is it for? For anyone who wants to understand what research shows on autism and sex/gender, above all on the question of why more boys than girls receive a diagnosis.

In brief

In studies, clearly more boys than girls with autism are recorded. A 2017 meta-analysis (54 studies, 13.8 million people) found a ratio of about 4.2 to 1, in high-quality studies about 3.3 to 1; the authors concluded that the true ratio is closer to 3:1 and that girls have an increased risk of not receiving a diagnosis. [3] A Swedish register study found that the ratio narrows with rising age at diagnosis. [1] A review named as possible hurdles in girls and young women, among other things, compensatory behaviour and prejudice in assessment. [2] Why the ratio exists is not clarified.

This English translation was produced with AI assistance and has not yet been independently reviewed.

How big is the difference?

A large review of prevalence found on average about 4.2 times as many boys as girls recorded (range 0.8 to 6.1). [4] The meta-analysis by Loomes and colleagues evaluated 54 studies with 53,712 people with autism (43,972 boys, 9,740 girls) and found a pooled ratio of 4.2 (95 % confidence interval 3.8 to 4.6) with very large variation between the studies. [3] High-quality studies gave 3.3, studies that examined the general population regardless of an existing diagnosis 3.25, studies that included only those already diagnosed 4.6. [3] The authors concluded: the true ratio is more likely 3:1 than 4:1, and there is a diagnostic sex bias (girls who meet the criteria receive a diagnosis less often). [3]

Why girls might be diagnosed later or not at all

A Swedish register study with 2,756,779 people found that the ratio of male to female diagnoses narrows with rising age at diagnosis (about 1.2 up to the age of 20); this suggests that many girls and women are diagnosed later. [1] Why, the study did not examine. A systematic review (20 papers, on girls and young women under 21 years) named as perceived hurdles: compensatory behaviour, parents’ concerns, perception by others, lack of information and resources as well as bias among professionals. [2] It also named sex-related features, for example in social and communicative skills, relationships, additional diagnoses and repetitive behaviour and interests. [2] More: Women and autism: why the diagnosis often comes later, Masking: when adapting is exhausting.

What can distort the research itself

In its introduction, the review stated that male and female pictures of autism are hard to separate, also because of mostly male samples in research and because of clinical instruments that fit the male presentation and may not be sensitive to differences in the distribution of features in women. [2] Note: this is a reproduction of the review’s introduction, not a result of its own.

What do we know – what is still open?

Study-based (meta-analysis, register study, review): More boys recorded; the true ratio probably lower; diagnostic bias likely; the ratio narrows with later diagnosis. [3; 1]

Open:

  • Whether and how strongly biological differences contribute to the ratio, the papers read do not show. The authors of the review considered it possible that the high ratio partly reflects the causes of autism. [2]
  • The studies mostly look at a binary sex model; on non-binary people and gender identity, no studies were evaluated here.
  • The review covered only English-language papers and few studies that had sex comparisons as their main question. [2]
  • The editorial team has not evaluated figures for Germany.

What else you should know

Note: This article offers general information. It does not replace personal advice or treatment by professionals.

Sources and literature

  1. Fyfe C, Winell H, Dougherty J, Gutmann DH, Kolevzon A, Marrus N, Tedroff K, Turner TN, Weiss LA, Yip BHK, Yin W, Sandin S. Time trends in the male to female ratio for autism incidence: population based, prospectively collected, birth cohort study. BMJ 2026;392. https://doi.org/10.1136/bmj-2025-084164 – Observational study (register)
  2. Lockwood Estrin G, Milner V, Spain D, Happé F, Colvert E. Barriers to Autism Spectrum Disorder Diagnosis for Young Women and Girls: a Systematic Review. Review Journal of Autism and Developmental Disorders 2021;8(4):454–470. https://doi.org/10.1007/s40489-020-00225-8 – Systematic review
  3. Loomes R, Hull L, Mandy WPL. What Is the Male-to-Female Ratio in Autism Spectrum Disorder? A Systematic Review and Meta-Analysis. Journal of the American Academy of Child and Adolescent Psychiatry 2017;56(6):466–474. https://doi.org/10.1016/j.jaac.2017.03.013 – Systematic review with meta-analysis
  4. Zeidan J, Fombonne E, Scorah J, Ibrahim A, Durkin MS, Saxena S, Yusuf A, Shih A, Elsabbagh M. Global prevalence of autism: A systematic review update. Autism Research 2022;15(5):778–790. https://doi.org/10.1002/aur.2696 – Systematic review

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