[lumberjack]

To me it is not obvious. What causation do you think is at play here? A lot of commenters seem to think it is some kind of emotional mechanism, mentioning things like social media and such. But it might just be a physical mechanism, like being too sedentary, or eye fatigue.

[username90]

Reading a book on a screen is basically the same as reading a physical book. There is no reason one would cause depression while the other wouldn't, unless it is due to the physical screen which is a problem that can be fixed. I've never seen a study saying that reading books causes depression, so it shouldn't.

[waterhouse]

How about something like e-ink? That's a screen, but in terms of optical properties I believe it should resemble paper.

[lumberjack]

I never tried e-ink for prolonged times, but I always found the contrast to be a bit lacking, which is something that contributes to eye fatigue. Last I used such devices was over 5 years ago though, so maybe technology has improved now.