A startup’s bold plan for a mood-predicting smartphone app is shadowed by questions over evidence

In the world of digital health, Silicon Valley-based Mindstrong stands out. It has a star-studded team and tens of millions in venture capital funding, including from Jeff Bezos’ VC firm.

It also has a captivating idea: that its app, based on cognitive functioning research, can help detect troubling mental health patterns by collecting data on a person’s smartphone usage — how quickly they type or scroll, for instance.