This teen's struggle with depression led her and brother to create app to help others

— -- When Hannah Lucas was diagnosed last year with a medical condition that caused frequent fainting, she felt scared and alone.

“I started passing out more and more often and I was terrified of going anywhere,” Hannah, 15, told ABC News. “Because what if I passed out and no one was around or what if someone took advantage of me?”

Hannah, a high school sophomore from Georgia, became anxious and depressed and started to self-harm, she said.

From that dark point in her life, Hannah and her younger brother, Charlie Lucas, 13, created an app to help people in distress.

The idea for the notOK App came from Hannah, who told her mom she wished there was an app she could use to quickly alert her family and friends when she needed help either physically or emotionally.

Charlie heard his sister’s idea and used coding skills he learned in summer camp to design the app.

“I helped illustrate it out so he would know what to do,” Hannah said of her brother. “He looked at my drawings and he coded it to tell the coders exactly what I wanted and how I wanted it to look.”

Charlie said his motivation for building the app came from watching his sister spiral into depression.

“I saw Hannah depressed, and she told me about her idea, and I started wire-framing it,” he said. “Making this app made her feel better and that made me feel better.”

Hannah pitched the app while taking a summer class on entrepreneurship at Georgia Tech. Professors there were so intrigued by the siblings’ creation that they connected the family with a development company in Savannah.

Over the course of five months, Hannah and Charlie worked side by side with the developers, often over Skype, to see their idea for the app turn into reality.

They also compiled research on mental health statistics to make the case that their app would find an audience.

Mental illness is defined by the National Institute of Mental Health (NIMH) as a mental, behavioral, or emotional disorder. One in six U.S. adults lives with a mental illness, the institute reports.

Among adolescents, an estimated 49.5 percent between the ages 13 to 18 have a mental disorder, according to NIMH.

NotOK was launched this week in both iOS and Android versions. The app, which comes with a $2.99 monthly fee, allows users to press a button that sends a text message to up to five preselected contacts.

The text, along with a link to the user's current GPS location, shows up on the contacts' phones with the message, “Hey, I'm not OK. Please call me, text me, or come find me.”

“The reaction we’ve heard has been really positive, especially from parents and kids suffering with anxiety,” Hannah said. “Those kids don’t know the words to tell somebody.”

Hannah added of the app, “It definitely gave me a sense of comfort.”