iGen: Why Today's Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy--and Completely Unprepared for Adulthood--and What That Means for the Rest of Us

by Jean M. Twenge

So smartphones could be causing lack of sleep, which leads to depression, or the phones could be causing depression, which leads to lack of sleep. It’s all rooted in the allure of the phone: when the phone calls its siren song, teens crash into the rocks instead of crashing into their beds.