Why Autism in Girls Is So Often Missed

A few weeks ago, a close friend told me that she was recently diagnosed with autism. I was astonished at the news: As long as I’ve known her, she has never demonstrated any of the stereotypical characteristics of the condition, such as challenges with communication and social interactions, and restricted or repetitive physical behaviors. She assured me that the diagnosis did indeed fit with her experience, and it was incredibly useful in making sense of some of the struggles she experienced throughout her life.

As a developmental psychologist, I am not a clinician, but I am a keen observer of social interactions, so I was super surprised that I was so clueless about her condition for so many years. But it turns out that recognizing autism in women and girls isn’t all that easy.

Autism spectrum disorder (ASD or autism) is a neurodevelopmental condition that starts in late infancy or early childhood and persists throughout life. Clinicians used to think of autism as a rare psychological condition, with a diagnosis of about 1 out of every 5,000 kids. But in the early 2000s, autism diagnoses went up from 1 in 5,000 to about 1 in every 31 kids, which is such a huge increase that people are still asking whether the U.S. is facing an autism epidemic.

However, around the same time, the criteria for autism expanded in the DSM-5 (the diagnostic manual that most clinicians use), combining Asperger’s and pervasive developmental disorder into the single category of ASD. This both increased public awareness of the condition, and screening for it.

So the number of people with the condition didn’t necessarily go up, but diagnoses did because we were more aware of what we are looking for. Indeed, autism isn’t caused by anything specific in the environment; it is predominantly genetic, and researchers estimate that genetic factors account for between 64 to 91 percent of the incidence of autism (Cook et al., 2024). So there isn’t necessarily any reason to believe that changes in the environment could have caused an uptick in cases.

Source: Royalty Free Photo from Pickpik

Importantly, autism is more common in males than females, by a factor of about 4 to 1. In fact, it is so much more common in males than females that researcher Simon Baron-Cohen (who happens to be the first cousin of the famous Sacha Baron-Cohen) even theorized that autism is an exaggeration of the male brain. He argued that the male brain is designed for analyzing patterns and rules while the female brain is more about social interactions and empathy. Using this framework, he suggested that autism is a representation of the most extreme version of men, which is why it is more common in males than females (Baron-Cohen, 2002).

His theory, however, has been heavily criticized for being based on gender stereotypes instead of any actual real data or evidence. In fact, Dr. Baron-Cohen has since acknowledged that using the term “extreme male brain” was problematic and likely perpetuated myths about biological sex differences in the brain that were most likely just socialized behaviors based on our societal expectations about the ways in which men and women should behave.

More recent research has suggested that biases in how the condition is diagnosed is what makes it more likely that males will get diagnosed. First, although autism is heavily genetically based, it is not linked to a single gene, so it isn’t something that there is a biological test for. Instead, we have to diagnose it from an individual’s behavior.

Further, the behaviors that autistic children present with vary widely, which is why we consider it a spectrum. Second, and most importantly, the autistic behaviors characteristic of girls are often different than the behaviors more common of boys.

For example, one of the criteria for diagnosing autism is difficulty making friends. However, this difficulty seems to primarily be true for autistic boys, who report fewer close friendships than do neurotypical boys; in contrast, autistic girls tend report the same levels of closeness with their friendships as anyone else. And since girls appear to be more motivated than boys to interact with their peers, they also tend to be better at hiding their autistic traits and often learn to mimic the ways neurotypical girls socialize so that they don’t stand out (Young et al., 2018). This makes it even harder for clinicians or doctors to catch, since they only observe people for short periods of time where girls can easily camouflage their symptoms.

Further, the most widely accepted tools for diagnosing autism were created based on the symptoms that boys experience, since it was thought to be so much more common in boys than girls. These diagnostic tools, such as the ADOS were also tested and validated on groups of all male samples, making them specifically designed to account for the symptoms of autism in males only. As a result, symptoms more commonly associated with autistic girls like camouflaging aren’t even included in standardized assessments, making it more likely that girls will slip through the cracks.

Similarly, autistic girls are also more likely to demonstrate other mental health conditions than boys, especially anxiety and depression. Autism itself is not a mental health condition or a disordered mental state—it is now thought of as a form of neurodiversity, or a different way of processing information. However, autistic people are at higher risk for developing other mental health problems. In fact, it is estimated that up to 70 percent of autistic individuals have at least one mental health problem, especially girls (Cook et al., 2024). These mental health issues will often overshadow autistic characteristics during assessment, and girls will end up with an anxiety or depression diagnosis instead of one for autism.

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All in all, when these factors are considered, researchers have estimated that autism is still more common in males than females, but by a factor of 3 to 1 or 2 to 1 instead of 4 to 1. We still have a long way to go in terms of tools for diagnosing autism in girls. But the good news is now that clinicians are starting to recognize the differences between autistic boys and girls, we can move closer and closer to developing diagnostic tools that are inclusive of everyone, regardless of gender.