Autism in young girls is often misdiagnosed or overlooked. A doctor explains why.

When 16-year-old Cosi was in sixth grade, 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.