(3 Jan 2019) LIKE MANY TEENAGERS AROUND THE COUNTRY, LAUREL FOSTER USES HER PHONE A LOT. SOUNDBITE (English) Laurel Foster, study participant: "I use Instagram. I use Snapchat."/ "I definitely use social media, probably more than I should but I really like to keep up with my friends especially ones that don't live nearby." BUT ALL THAT CONNECTIVITY CAN COME AT A PRICE. STUDIES HAVE LINKED HEAVY SMARTPHONE USE WITH WORSENING MENTAL HEALTH AMONG TEENAGERS. SOUNDBITE (English) Laurel Foster, study participant: "I definitely know that like at least half of my grade has struggled with depression. I mean, at age 15, I feel like that's not very good." IT'S NOT ONLY ANXIETY. GOVERNMENT DATA SHOWS THAT TEENAGE AND YOUNG ADULT SUICIDE RATES AND DEPRESSION HAVE RISEN IN RECENT YEARS. SOUNDBITE Ian Gotlib, Stanford University psychologist: "It's not clear why this prevalence is increasing." BUT THE VERY DEVICE CONTRIBUTING TO TECH-AGE ANGST COULD NOW BE A TOOL TO MEASURE MENTAL HEALTH. SOUNDBITE Ian Gotlib, Stanford University psychologist: "If we can have an algorithm that in kids predicts the onset of depression by a change in their smart phone usage or mobility, or how they're responding to certain pushed questions on a smartphone, then we have an opportunity to start to develop technology based prevention programs." IN AN ON-GOING STANFORD UNIVERSITY STUDY, RESEARCHERS HAVE INSTALLED AN APP THAT TRACKS PHONE ACTIVITY. CHANGES IN TYPING SPEED, VOICE TONE, WORD CHOICE, HOW OFTEN KIDS STAY HOME ARE AMONG SMARTPHONE SIGNALS THAT PRELIMINARY STUDIES SUGGEST MIGHT BE LINKED WITH DEPRESSION. STUDY PARTICIPANTS ALSO ANSWER QUESTIONS ON HOW THEY'RE FEELING ON THE APP. AFTER A LIVE-STREAMED SUICIDE LAST YEAR, FACEBOOK PROGRAMMED ITS A-I SYSTEMS TO FLAG CERTAIN WORDS OR PHRASES IN ONLINE POSTS. BUT MEASURING A TEEN'S PRIVATE ACTIVITY RAISES CONCERN. SOUNDBITE (English) David Ryan Polgar, Tech Ethicist, All Tech is Human: "This is the thorny ethical issue that we're really going to have to work out to determine what is that teen's right to freedom of mind. Do they have a right and I think they do, to not be under constant surveillance?" BACK IN SAN FRANSISCO, FOSTER IS IN HER FIFTH YEAR OF PARTICIPATING IN THE STUDY. RESEARCHERS SAY THE ULTIMATE GOAL WOULD BE TO OFFER REAL-TIME HELP WITH AUTOMATED TEXT MESSAGES OR ALERTS TO PARENTS. SOUNDBITE (English) Laurel Foster, study participant: "I think the app actually it made me feel pretty good because like I feel like a lot of teens don't acknowledge their emotions and I feel like actually seeing them and saying OK I am stressed what can I do about that is a pretty healthy mechanism for coping with your stress." DIGITAL FOOTPRINTS GIVING RESEARCHERS NEW INSIGHT INTO GROWING UP IN A DIGITAL AND STRESSFUL WORLD. KRYSTA FAURIA, ASSOCIATED PRESS Find out more about AP Archive: http://www.aparchive.com/HowWeWork Twitter: / ap_archive Facebook: / aparchives Instagram: / apnews You can license this story through AP Archive: http://www.aparchive.com/metadata/you...