> Whatever the safe level of smartphone usage is, most of us are above it.

I think I'm immunized from it because I hate using smartphones, especially when I'm at home and could be doing the task on a PC with a big screen and keyboard. I have a few but just use them for practical tasks when away from home (occasional text, deliveries on porch, looking something up in the store, listening to podcasts, to do list for the day). Viewing content on a tiny screen with a minefield of things to accidentally tap? No thanks. They are great multi-function devices to replace others on the go.