The suicide rate of girls from 15 to 19 has doubled from 2007 to 2015; while researchers have several theories, they aren't quite sure what's brought about the increase.

In 2015,  524 deaths were marked as suicides among teen girls, the highest number since 1975, according to the Centers for Disease Control and Prevention.

The higher number could be, in part, due to medical examiners and coroners ruling more deaths suicide, said Carolina Hausmann-Stabile, a mental health researcher at Bryn Mawr College. In the past, they might have labeled a death accidental due to stigma and a desire to protect families.

Still, she said, the numbers are troubling, and it's important to look at social realities.

"We cannot explain the increase in death by suicide just by saying more people are depressed, and we are going to fix it by putting Prozac on the corner, you know, like a dispenser," she said.

Rates of suicide go up in periods of social turmoil, such as the recent Great Recession, she said. But those who die by suicide almost always have problems with their families and feel hopeless about the future.

It's important to recognize that multiple factors drive suicide, said Terri Erbacher, a school psychologist in Delaware County and a professor at Philadelphia College of Osteopathic Medicine.

And stigma has remained a huge issue.

"If you're worried about a friend, just ask. And really, truly listen," she suggested. "'Seems like you've
been down and out, are you having thoughts of suicide?' And really ask the question directly. That's the biggest thing."

All school staff in Pennsylvania are now trained in suicide prevention and warning signs, which means  teachers are referring more kids to Erbacher.

As for the possible negative role of social media, Erbacher and Hausmann-Stabile are both agnostic.

Social media creates shallow connections among teens, Hausmann-Stabile said, while meaningful connections can serve as a protection against adversity.

Erbacher said suicide is too complex to boil down to one issue, but she said it's hard for her students who face cyberbullying to take a digital break — even for just one night.

Helping families through parenting classes and developing interventions for schools can help bring down teen suicide rates, said Hausmann-Stabile. And teens can try new apps — including A Friend Asks and Ask and Prevent Suicide — to help their friends.