Autism rates are ‘more or less equal for men and women’, according to a study which challenges previous assumptions about its prevalence.
While the neurological and developmental condition is known to be more common in young boys, Swedish researchers found there was a big rise in diagnoses among adolescent girls.
And by the age of 20, the male-to-female ratio had evened out at nearly one-to-one, experts at the Karolinska Institutet reported.
Researchers said the study, published in the BMJ, highlights a need to investigate why girls and women receive diagnoses of autism spectrum disorder (ASD) later than boys and men.
Previous work on gender and autism suggested that for every four men or boys diagnosed with autism, there would be one woman or girl.
A study in 2017 suggested this figure may be closer to three men to one woman.
But in the latest research from Sweden, academics examined diagnosis rates of autism for all people born in the country between 1985 and 2000 – more than 2.7 million people – and tracked them until 2022.
During this period, some 2.8% of people were diagnosed with ASD.
They found that the male-to-female ratio of diagnosis decreased over time to the extent that it “may no longer be distinguishable by adulthood”.
The study did not account for genetics or environmental factors or for other conditions associated with autism, such as attention deficit hyperactivity disorder and intellectual disability, which might have played a role in patients’ diagnoses.
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Commenting on the study, Dr Rachel Moseley from Bournemouth University, said the findings provide “important support for what autism researchers have known for a long time” about a substantial gap in diagnosing autism in females.
She added that studies of children may miss autistic features which are already present in males but not yet visible in females.
The high male-to-female ratio has also been attributed to better social and communication skills among girls, making autism more difficult to spot.
Dr Judith Brown, from the National Autistic Society, said “women and girls are more likely to ‘mask’ what is traditionally thought of as signs of autism, making it harder to identify the challenges they face”.
She added that the results “highlight the fact that gender should never be a barrier to receiving an autism diagnosis and access to the right support”.
