Does autism really affect mostly boys? A large study from Sweden published by The BMJ suggests the answer is no. Researchers tracked 2.7 million people born between 1985 and 2022, following them for up to 37 years. They found that autism was diagnosed in 78,522 individuals—but boys and girls were diagnosed at very different ages.
Historically, autism has been diagnosed in boys about four times more often than girls. This huge gap has led many to believe autism is simply more common in males. But this study reveals a different story: the real difference is timing.
Girls' autism diagnoses peak years after boys'
Boys reached their highest diagnosis rate between ages 10–14 years. For girls, the peak came later—between ages 15–19 years. By age 20, the ratio of boys to girls diagnosed with autism had nearly evened out to 1:1, suggesting similar actual rates.
This five-year delay matters because a girl missing out on diagnosis during childhood misses years of potential support in school and at home.
Why the delay happens remains unclear
The researchers believe girls' stronger early social and communication skills can mask autism signs. However, the study couldn't fully explain why diagnosis happens so much later for girls. The research also couldn't account for other linked conditions like ADHD, or genetic and environmental factors like parental mental health.
Because this is a Swedish population study, findings may not directly apply to Singapore families, though the pattern is likely relevant across different countries.
Recognise that your teenage daughter may still need an autism assessment
- If your daughter shows signs of autism (difficulty with social interaction, repetitive interests, sensory sensitivity), seek assessment even if she seemed fine in primary school.
- Know that girls often develop better social coping strategies, which can disguise autism—don't assume an articulate, socially active teen cannot be autistic.