Women tend to be diagnosed with autism spectrum disorder (ASD) less often than men. Is this because less women have ASD or because the signs of ASD are not as easy to identify in women? Research from Kings College London suggests it may be the latter. The study finds that women with ASD exhibit fewer repetitive behaviors—a key criteria for diagnosing autism—than men. This can lead to many women receiving only a partial diagnosis of the disorder. Multiple studies have demonstrated that girls are diagnosed with ASD later and less frequently than boys. The present study offers one explanation for this phenomenon.
The researchers evaluated 935 men and 309 women (all aged 18 to 75) whose primary physicians had referred them to an autism specialty clinic. They used two evaluations: the Autism Diagnostic Interview-Revised (ADI-R) and the Autism Diagnostic Observation Schedule (ADOS). Of the participants, 630 were evaluated with the ADI-R, which relies on parent reports, and 408 were evaluated using the ADOS. The researchers evaluated 206 participants using both assessments.
According to the assessments, 72 percent of the male participants and 66 percent of the female participants received an autism diagnosis. The researchers then narrowed the group to those with an ASD diagnosis and at least average intelligence. They examined the gender differences in autism based on the diagnostic categories for ASD in the International Classification of Diseases (ICD)-10: social interaction, communication, and repetitive behaviors/restricted interests.
Based on the ICD-10 criteria, 25 percent of the men and one-third of the women qualified for only a partial diagnosis of ASD. This is because they met only two out of three diagnostic criteria.
The results revealed that there was a big difference between men and women in the expression of repetitive behaviors and restricted interests. Women were less likely to meet the repetitive behaviors/restricted interests criteria and thus more likely to receive a partial diagnosis.
Study investigator C. Ellie Wilson, now a researcher at the University of Seville in Spain, says the findings indicate that women with ASD may not be receiving the services they need. “These women had severe social and communication deficits, but they were not getting a full autism diagnosis because they didn’t meet the criteria for repetitive behaviors. This is potentially problematic when you think about clinical support and the resources available to them.”
The findings highlight the sex-based differences in ASD between men and women. The results also suggest that the diagnostic process should take these differences into account.
This research is published in the journal Autism.