Key Findings from Swedish Study
A large-scale study suggests that females may have a similar likelihood of being autistic as males, despite boys being diagnosed up to four times more frequently in childhood. Research by the Karolinska Institutet in Sweden analyzed autism diagnosis rates among 2.7 million people born in Sweden between 1985 and 2020. Approximately 2.8% of these individuals received an autism diagnosis between the ages of two and 37.
Equal Prevalence by Adulthood
By age 20, diagnosis rates for men and women were observed to be nearly equal, challenging prior beliefs that autism is more prevalent among males. Lead author Dr. Caroline Fyfe stated that the findings suggest a lower gender difference in autism prevalence than previously assumed.
"Our findings suggest a lower gender difference in autism prevalence than previously assumed, potentially due to underdiagnosis or late diagnosis in women and girls." — Dr. Caroline Fyfe
Disparities in Childhood Diagnosis
In childhood, boys received autism diagnoses approximately three years earlier than girls, with median ages of diagnosis being 13.1 for boys and 15.9 for girls. Boys were three to four times more likely to be diagnosed with autism under age 10.
However, diagnosis rates for girls increased significantly during adolescence, leading to similar overall rates by age 20. The authors concluded that these observations indicate a need to investigate the reasons for later diagnoses in female individuals compared to male individuals.
Evolving Trends in Diagnosis Rates
The study, published in the BMJ, also reported that gender disparities in diagnosis rates remained consistent for children under 10 over the last three decades, but decreased quickly for other age groups.
The authors observed that the male to female ratio for autism spectrum disorder has decreased over time and with increasing age at diagnosis. This suggests that the ratio might be substantially lower than previously thought, potentially becoming indistinguishable by adulthood in Sweden.
Expert Commentary and Implications
Systemic Biases in Diagnosis
In a linked editorial, patient advocate Anne Cary stated that the research supports the argument that systemic biases in diagnosis, rather than a true difference in incidence, account for the discrepancy in diagnosis rates.
Cary suggested that while symptom onset could be delayed and masking is a factor, autism diagnostic methods and tools might contain biases requiring refinement. She indicated that these biases could result in a girl who would eventually be diagnosed with autism having less than a one-third chance of receiving a diagnosis before age 10.
As autistic girls and women await proper diagnosis, they may receive misdiagnoses of psychiatric conditions, particularly mood and personality disorders, and often need to self-advocate for appropriate treatment as autistic patients. — Anne Cary
Addressing Gender Stereotypes
Autism charities responded to the findings by stating that more effort is needed to address gender stereotypes. Dr. Judith Brown, head of evidence and research at the National Autistic Society, emphasized that gender should not impede autism diagnosis and support.
Dr. Brown explained that while historical assumptions favored autism being more common in males, women and girls are now understood to often mask traditional signs of autism, complicating identification. She highlighted that misdiagnosed autistic women can develop coexisting mental health difficulties, such as anxiety and depression, due to lack of support and the effort required for masking. She stressed the importance of acknowledging the experiences of autistic women and girls and discontinuing outdated stereotypes.
Jolanta Lasota, chief executive of Ambitious about Autism, commented that autistic girls have different experiences than autistic boys and have often been overlooked. She added that misunderstanding their needs or attributing them to other causes has resulted in missed support and, in some cases, mental health crises.
Lasota emphasized the importance of researchers and diagnostic services continuing to develop an understanding of autism's varied presentations in girls and women, and for support services to adapt to accommodate the growing number of individuals requiring assistance.
Clinical Observations and Future Needs
Dr. Conor Davidson, clinical lead for Leeds autism diagnostic service, noted that autism in girls is more frequently undetected during childhood, with signs potentially emerging in adolescence or early adulthood. He stated that adult neurodevelopmental clinics in the UK have recently observed an increase in women seeking assessments compared to men.
Dr. Davidson pointed out that waiting lists for both child and adult autism assessments are extensive. He stressed the importance of timely assessment and care for autistic women who have not received a diagnosis and highlighted the need for psychiatrists to consider autism when evaluating patients, especially women whose autism may have been overlooked in childhood.