Stockholm: Autism may be just as prevalent among females as males, but boys are up to four times more likely to be diagnosed in childhood, according to a large-scale Swedish study that challenges long-standing assumptions about gender and autism.
The research, led by the Karolinska Institutet, examined autism diagnosis rates among 2.7 million people born in Sweden between 1985 and 2020. The study tracked diagnoses made between the ages of two and 37 and found that 2.8 percent of the population received an autism diagnosis during that period.
While childhood diagnosis rates showed a clear gender imbalance, the gap narrowed significantly with age. By the time individuals reached 20 years old, autism diagnosis rates among men and women were almost identical. This finding directly challenges the belief that autism is inherently far more common in males.
Lead author Dr. Caroline Fyfe remarked that the results suggest that the true gender difference in autism prevalence is much smaller than previously thought. She explained that the apparent disparity is largely due to girls and women being underdiagnosed or diagnosed much later than boys.
The study found that, on average, boys were diagnosed nearly three years earlier than girls. The median age of diagnosis was 13.1 years for boys, compared with 15.9 years for girls. Overall, boys were three to four times more likely than girls to be diagnosed with autism before the age of 10.
However, girls were found to ‘catch up’ during adolescence, as diagnosis rates among females increased rapidly in the teenage years. By early adulthood, the male-to-female ratio had largely evened out.
The researchers noted that while gender differences in diagnosis for children under 10 have remained relatively stable over the past three decades, these disparities declined quickly in older age groups. They observed that the male-to-female ratio for autism spectrum disorder has decreased both over time and with increasing age at diagnosis.
According to the authors, this suggests that in Sweden, autism prevalence by adulthood may no longer show a meaningful gender difference. They concluded that further investigation is needed to understand why girls and women tend to receive diagnoses later than males.
In an accompanying editorial, patient and patient advocate Anne Cary highlighted that the findings support the argument that systemic diagnostic bias, rather than a real difference in autism incidence, is driving the gender gap. While delayed symptom onset and masking play a role, she said diagnostic tools and clinical methods themselves may be biased and in need of refinement.
Cary pointed out that these biases mean a girl who will eventually receive an autism diagnosis has less than a one-in-three chance of being diagnosed before the age of 10.
As a result, many autistic girls and women are misdiagnosed with psychiatric conditions, particularly mood and personality disorders. She added that they are often forced to self-advocate to be recognised and treated appropriately as autistic patients, just as autistic as their male counterparts.
Autism charities responded by calling for stronger efforts to challenge gender stereotypes in diagnosis and support. Dr. Judith Brown, Head of Evidence and Research at the National Autistic Society, said that gender should never prevent someone from receiving an autism diagnosis or accessing the right support.
The Head noted that autism was historically and incorrectly viewed as a condition affecting mostly boys and men. Today, evidence shows that women and girls are more likely to mask behaviours traditionally associated with autism, making their difficulties harder to identify.
Jolanta Lasota, Chief Executive of Ambitious about Autism, stated that autistic girls have had different experiences from boys and have gone unnoticed for far too long. Lasota added that their needs are often misunderstood or explained away, causing many to miss out on vital support and, in some cases, reach a crisis point with their mental health.
Dr. Conor Davidson, Former Autism Champion at the Royal College of Psychiatrists and clinical lead for the Leeds autism diagnostic service, said autism in girls is more likely to go undetected in childhood. In many cases, signs only become visible during adolescence or early adulthood.
Davidson noted that adult neurodevelopmental clinics in the UK have recently seen increasing numbers of women seeking assessments, sometimes outnumbering men. However, he warned that waiting lists for both child and adult autism assessments remain unacceptably long.
Dr Davidson said many autistic women are still living without a diagnosis and must be able to access timely assessment and care when needed. He added that psychiatrists should be alert to the possibility of autism when assessing patients with mental health problems, particularly women whose autism may not have been recognised earlier in life.
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