In a new paper published in Clinical Psychological Science, my colleagues and I found that the increases in depression, suicide attempts and suicide appeared among teens from every background: more privileged and less privileged, across all races and ethnicities, and in every region of the country. All told, our analysis found that the generation of teens I call “iGen” — those born after 1995 — is much more likely to experience mental-health issues than their millennial predecessors.

What happened so that so many more teens, in such a short time, would feel depressed, attempt suicide and commit suicide? After scouring several large surveys for clues, I found that all of the possibilities traced back to a major change in teens’ lives: the sudden ascendance of the smartphone.