Between four and five times as many boys as girls are diagnosed with ASD each year. The same has been more or less true ever since the first cases of autism were described in the 1940s. And while there have been considerable improvements in the development of support and understanding of the needs of autistic people, the ratio has remained relatively static.
Despite the remarkable consistency, no mechanism has been proven to definitively account for this difference.
Various hypotheses exist. The well-known but much criticised, ‘extreme male brain’ theory, suggests that exposure to high levels of testosterone during gestation primes fetal brains to be more male-like, enhancing tendencies such as spotting patterns in the world and thinking systematically while diminishing female-like traits, such as empathy and the ability to observe social cues.
Another popular theory is the female protective effect, which proposes that females are genetically more resistant to certain factors that increase the likelihood of autism in an individual.
This is idea is supported in a new study led by Yale University which found that autism appears to develop in a different part of the brain for males and females. Researchers also found females with autism to have a larger number of genetic mutations, suggesting that girls require a greater 'genetic hit' to develop autism than boys do.
In time, these findings may play an important role in advancing our understanding of what makes some people more resilient to developing autism. But when looking at it purely from a diagnosis perspective – why more boys are diagnosed than girls - it’s important to consider a variety of contributing factors.
Speaking in a recent panel on autism in females chaired by Neurodevelopmental Specialist, Emma Woodhouse, autistic researcher and author, Hannah Belcher explained, "From the research that myself and others have done, there seems to be less obvious social traits in females. So when they're tested, they often don't score as highly for problems in social communication. And when I did my study looking at undiagnosed women, they tended to have better social functioning and empathy, which can easily mask autistic traits."
Historically, the diagnostic measures have been based largely on a male perspective due to the stereotypical view of autism. If a girl doesn't fit this profile, their symptoms can easily be misinterpreted as something else. As a result, many females with autism are misdiagnosed and miss out on the support they need.
Also speaking was Dr Pooky Knightsmith, who explained how these stereotypes can cause many issues when trying to spot autism in girls. "There are lots of things that we've become good at spotting in boys or in girls who present in a more typically male way. But when that presentation isn’t typical, we often miss it.”
"One of the difficulties is that it's often not yet fully understood how variable the ways that autism presents itself can be. And if an autistic person doesn’t show the typical characteristics, it might not occur to people that they might be autistic, or it's written off because of all the misconceptions."
Because no single symptom means that you must have a diagnosis - and because there isn't a single symptom that means you can rule out a diagnosis - we must consider a variety of factors when trying to diagnose autism in females.
Special interests are one of the most common characteristics of people with autism. Again, this can present differently in females, as Pooky explained. "Let’s say we have a young boy who obsesses and is always playing with toy trains or other vehicles. Many people will say things like, 'Oh, maybe he's autistic.' But if a girl is equally obsessed but about, for example, pop stars or ballet or animals, then it’s more socially acceptable and we don’t think to question it."
An autistic girl might have a special interest similar to that of a neurotypical girl but may not be recognised for her special interests. The intensity of her interest is what makes her different from the neurotypical girl, and this can present itself in several ways, such as the way she talks.
While many autistic children don't speak much, others may talk about their special interest frequently and in great detail. For autistic girls, their speech may appear neurotypical but typically, they tend not to engage in small talk, and this can be a problem when interacting with other girls during childhood and adolescence.
This can lead to girls with autism naturally developing mechanisms to help them to interact with people more successfully.
One of these methods is ‘masking’ or ‘camouflaging’, as Pooky explained, “Females are often very good at mimicking and blending in - in doing what's needed. This can come at a huge cost to themselves and means that we often don't pick up on important issues.”
“The first thing to note is that it’s very tiring. The trouble is, that from a personal standpoint, you probably don’t know you’re doing it. My 11-year-old daughter is autistic. When hearing about the things she finds hard at school and then reflecting on my own school days, I wonder how I got through it. For me, the cost was that I would put on a face to everyone else.”
Hannah added, “I stopped going to school when I was 14 because I just ran out of social scripts. I worked my way up to that point and then everything accelerated too quickly, and I just couldn't do it anymore. It was very tiring.”
“Everyone learns to camouflage growing up. Everyone learns to copy other people. And that's how you become social beings. But when you're autistic, you have to pretend to be something you’re completely not. You have to take on a way of thinking that isn't natural to you, and it's constant, and it's all the time.”
Unfortunately, there simply hasn't been enough research into whether masking is a protective or harmful mechanism. What we do know is that it has led to countless wrong diagnoses of female autism.
The concerted effort to find out what’s happening with women who are getting missed or misdiagnosed has been a hot topic in research circles for several years. Yet it's only recently that specialists in neurodevelopmental disorders have widely accepted that autism is not limited to boys and men.
Understanding why females are underdiagnosed is vital. The National Autistic Society's 2012 study found that 42% of females had been wrongly told they suffered psychiatric, personality or eating disorders, compared with 30% of males. Meanwhile, just 8% of girls with Asperger syndrome were diagnosed before the age of six, compared with 25% of boys.
Of the adult females who took part in the study, many didn’t have a formal diagnosis, and many of those with one had only received it because they had taken it upon themselves to pay for a private opinion.
While attitudes are slowly changing, more research needs to focus on how autism affects both genders differently, and how we can ensure gender doesn’t prevent people from accessing the support and services they need.
If you are wondering about your own experiences, taking a free online test could be the first step to getting the correct support. But, as we always remind people, an online test is only a guide. Receiving a formal diagnosis comes as the result of a far more comprehensive process conducted by a psychologist, psychiatrist, or neuropsychologist who specialises in autism assessments.