Studies have revealed that Women with autism often go undiagnosed or receive either a partial diagnosis or a diagnosis that is years overdue. This may be because females with Autism present with fewer repetitive behaviours than males with Autism on standard diagnostic tests. For every one girl diagnosed with autism there are 10 boys diagnosed.
With so many more males diagnosed, most of the diagnostic assessments are based on research in boys with autism and may be biased toward behaviours typically seen in males. So it is unclear whether less females have autism, or that the features of autism in females are just distinctly different and harder to recognize. In either case, these females that go undiagnosed in childhood will often go undiagnosed or struggle to gain a diagnosis as adults.
The most striking thing is the difference in repetitive behaviours between males and females, says Grainne McAlonan, clinical reader in translational neurodevelopment at Kings College London and a senior researcher on the study. That may have an impact on the way we recognize autism in females, and consequently whether those females get access to services.
Researchers evaluated 935 males and 309 females aged between 18 and 75 years old, referred to an autism specialty clinic by their general practitioner. A standard assessment called the Autism Diagnostic Interview-Revised (ADI-R) was used.
This assessment relies on parent or caregiver reports to document the behaviour of 630 adults when they were children. The Autism Diagnostic Observation Schedule (ADOS), was then used to directly evaluate the social and repetitive behaviours of 408 adults whose parent reports were not available. Another 206 participants were also assessed using both tests. The test results in conjunction with a psychiatric exam resulted in 72 percent of the males and 66 percent of the females received an autism diagnosis.
Researchers then focused their analysis on adults with autism who have at least average intelligence to examine gender differences in autism signs on each of the three diagnostic domains in the World Health Organization’s International Classification of Diseases (ICD)-10: social interaction, communication, and repetitive behaviours or restricted interests. Most females they diagnosed showed strong signs in one area, usually either communication or social interaction, and moderate or mild signs in the other two domains. Males however typically showed moderate signs across all three domains.
The study highlights potentially important differences in the profiles of men and women with autism, says Thomas Frazier, director of the Center for Autism at the Cleveland Clinic in Ohio, who was not involved in the study. Men with autism tend to have features that span several diagnostic criteria, whereas women often show severe impairment in only one area, he says. Neither the ADOS nor the ADI-R measure the severity of traits, which may be key to spotting sex differences, says Begeer. Nor did the researchers look for differences in types of repetitive behaviour or sensory sensitivities. In studies of adults, such details can be hard to get because the ADI-R relies on parent or caregiver recollections from decades past. We really need to do prospective studies to try and identify what sex differences there might be, Wilson says.
The study has highlighted the possibility that females and males with autism present differently and therefore may benefit from gender specific diagnostic tools.