What Is the Male-to-Female Ratio in Autism Spectrum Disorder? A Systematic Review and Meta-Analysis.
Level 1 - systematic review of randomized trials
Systematic review and meta-analysis of prevalence studies
PubMed 28545751 · doi:10.1016/j.jaac.2017.03.013
What was done
Authors conducted a systematic review and random-effects meta-analysis following PRISMA guidelines to determine the male-to-female odds ratio (MFOR) in autism spectrum disorder (ASD) since the introduction of DSM-IV and ICD-10. Medline, Embase, and PsycINFO were searched, and study quality was assessed with a risk-of-bias tool. The pooled outcome was the odds of being male in the ASD group versus the non-ASD group.
What was found
Across 54 studies with 13,784,284 total participants (53,712 with ASD: 43,972 boys and 9,740 girls): - The overall pooled MFOR was 4.20 (95% CI 3.84–4.60), with substantial heterogeneity (I² = 90.9%). - High-quality studies yielded a lower MFOR of 3.32 (95% CI 2.88–3.84). - Studies screening the general population regardless of prior diagnosis yielded an MFOR of 3.25 (95% CI 2.93–3.62), compared to 4.56 (95% CI 4.10–5.07) in studies relying only on pre-existing ASD diagnoses.
Why it matters
The widely accepted 4:1 male-to-female autism ratio appears driven by diagnostic ascertainment bias. The true ratio is closer to 3:1, indicating that females meeting diagnostic criteria are systematically underdiagnosed in clinical practice.
Limits
Between-study heterogeneity was very high (I² = 90.9%). The findings depend on pooled observational prevalence studies with varying ascertainment methodologies, and the abstract does not report stratification by cognitive ability, age, or co-occurring conditions.
Cited by
- supports Autism has an incidence ratio of approximately 4:1 male to female in the United States.