Smartphones may often feel like a source of stress, feeding us an endless stream of bad news and social comparison. But what if they could also be the solution? A team of researchers believes they can be. The team has developed a smartphone app that delivers core techniques of cognitive-behavioral therapy (CBT) -- a proven treatment for depression and anxiety -- straight into the hands of users, and tested it in the largest-ever individually randomized trial of its kind. Their resilience training app, called RESiLIENT, was tested on nearly 4,000 adults across Japan experiencing subthreshold depression -- a form of low-level but persistent depressive symptoms that doesn't meet criteria for major depressive disorder but can still be debilitating. This condition affects an estimated 11% of people worldwide and often goes untreated.