AUSTIN (KXAN) – The prevalence of Autism Spectrum Disorder (ASD) has grown rapidly in the last couple of decades. Though the number of girls diagnosed with the developmental disorder has risen along with the overall numbers, doctors say that diagnosing girls with ASD is more challenging than with boys. 

ASD is a developmental disability characterized by persistent difficulties in social interaction and repetitive behaviors, interests or activities that make communicating and participating in daily activities more challenging, according to the CDC. 

The CDC first began tracking autism in children in Atlanta in 1996. In 2000, it established the Autism and Developmental Disabilities Monitoring (ADDM) Network, which expanded the tracking to nine more U.S. metropolitan regions. 

Since then, the prevalence of autism in children has markedly risen. In 2000, the network found that around one in 150 children had ASD. 18 years later, this number jumped to around one in 44.

And since 2018, it has risen even further. The CDC reported last month that one in 36 children in 2020 had autism, according to its data. And for the first time since the CDC began tracking autism, the prevalence of ASD in girls in 2020 has exceeded 1%. The rate for boys is around 4%. 

“We’re starting to understand that autism is not just a boy’s condition and that there are lots of girls out there who often have flown under the radar, until they’re teenagers or they’re adults when they start to realize ‘Gosh, maybe that’s why I’ve always felt different,’” Dr. Audrey Brumback, an assistant professor in neurology at the UT Austin Dell Medical School, said. 

Why have autism diagnoses spiked? 

Brumback said when scientists started talking about autism, the condition was blamed on “refrigerator mothers,” meaning mothers who were not overly loving. She said that theory was later thrown out when scientists started to understand there was a biological component to the disorder.

The prevalence in recent decades has increased mostly because doctors are better at diagnosing children with autism, Brumback said. Many people in the past were labeled as having other conditions – such as mental retardation – and now would likely be diagnosed with autism instead. 

In the new CDC report, the ratio of children diagnosed with autism is around 4 to 1 male to female. Brumback said that there is a biological component that partially explains why boys are more likely to be diagnosed with autism than girls but also that girls tend to be harder to diagnose. 

Why are girls harder to diagnose? 

“It’s easier for the women to fly under the radar,” Brumback said. 

This happens for a few reasons. 

“Girls tend to be sort of quietly autistic, where they’re not calling attention to themselves by doing all these things visible to outside observers. And so they’re just sort of quietly having challenges.”

She also said that girls are largely better than boys at picking up others’ behaviors.

“Girls are good at sort of copying and pasting other people’s behavior onto themselves,” Brumback said. For example, a girl may see a classmate who is socially popular with a large friend group and think of ways to mirror that classmate’s behavior to try and achieve what they have. 

Brumback said though it remains more challenging to diagnose girls with autism than boys, “we’re starting to close that gap,” she said. 

Signs to look out for 

Many girls with autism might have trouble at home but not at school.

“Basically, they’re using every molecule of energy that they have to mimic their neurotypical friends and appear to be neurotypical. We call it masking,” she said. “The teachers think everything’s fine — they’ve got a friend group and they’re doing great at their classwork.”

But in these situations, when the child comes home to a safe place, they might break down. 

“If you have a child who’s a teen, who’s coming to you melting down after school, press the pause button and ask yourself, could this person have autism?” 

And if a person discovers they might be on the autism spectrum later in life, Brumback said self-acceptance is paramount. 

“Just understand that there’s nothing wrong with you. It’s just that you’re wired up differently,” Brumback said.