The study, published in the British Medical Journal, analysed national registers covering 2.7 million people born in Sweden between 1985 and 2022. Over a follow-up period of more than 35 years, 78,522 individuals around 2.8% of the cohort were diagnosed with autism, at an average age of 14.3 years.
While boys were more frequently diagnosed in childhood, researchers found a clear “catch-up effect” among girls during adolescence. By the age of 20, diagnosis rates approached parity between males and females.
Researchers from Karolinska Institutet noted that the historical male-to-female ratio for autism may have been exaggerated due to diagnostic bias, rather than actual prevalence differences. Girls are often diagnosed later, likely due to better social and communication skills that mask symptoms.
Dr Rachel Moseley, a psychology expert at Bournemouth University, said the findings support previous evidence that autism is often undiagnosed in females, particularly older women. “Signs of autism in girls may only become visible at a later age, meaning many females remain unidentified in early childhood,” she explained.
The study highlights the importance of recognising and diagnosing autism in girls earlier, noting that undiagnosed autism can be linked to severe challenges, including mental health difficulties and increased risk of suicidality.
