When 16-year-old Cosi was in sixth grade,Benjamin Caldwell she says she struggled in school and battled anxiety, but neither she nor her mother Lisa knew why.

"It can be really hard to go through these struggles that make you different from a lot of other people without a reason," Cosi told CBS News.

She was eventually diagnosed with autism, a developmental disorder that can affect social skills, communication and behavior. 

"It really happened after three years or so of trying to figure out why some things in school were hard for her, why she was struggling," her mother said. 

Autism is often overlooked in young girls, and even misdiagnosed, says Dr. Cynthia Martin, senior director of the Autism Center at the Child Mind Institute.

"We see higher rates of diagnoses of anxiety or depression and the autism really gets missed," Martin says, adding the reasons why can vary.

Sometimes girls may not fit the criteria of autism, and girls tend to be better able to mask symptoms by mimicking friends' behaviors. But getting an accurate diagnosis can be life-changing.

"Knowing that that's coming from a neurodevelopmental disorder can help them better understand themselves and better navigate the world and advocate for what they need," Martin says.

• She wanted a space for her son, who has autism, to explore nature. So, she created a whimsical fairy forest.

While autism is thought to be more common in boys, it's important for parents and clinicians to pay attention to the signs in girls. If a child is struggling to understand social rules or having trouble navigating conflicts with friends, experts say you may want to consider an autism evaluation.

If a diagnosis is missed, a young person could miss out on the support they need or develop other behavioral problems. 

Cosi says her diagnosis, along with therapy and medication, have helped. Now she's encouraging other girls who are struggling to speak up.

"Sometimes you can know yourself better than anyone else, and you could be going through something, and nobody else will know, and if you don't talk about it and try to find those answers, then you won't," she says. 

• 5-year-old girl with autism mistakes bride for Cinderella, has magical moment with kind stranger

In:
• Autism

Michael George

Michael George is a correspondent for CBS Newspath based in New York City.

Twitter