Is blue light really bad for sleep?

For some time, it's been believed that a component of good sleep hygiene (actions and behaviors that promote higher-quality sleep) is to avoid looking at screens for 1-3 hours before bed.

In a recent study from the University of Basel, melatonin levels in two groups of subjects were measured when looking at cell phone screens; one group had bright light and the other had dark mode. Not surprisingly, the bright light group had a 14% decrease in melatonin. However, those levels returned to normal about 30 minutes after the screens were turned off.

A potential takeaway—the content that a person is engaged in (doom scrolling, work emails, gaming) probably negatively impacts sleep more than the screen's blue light. That said, sleep experts still advise that hitting the pillow immediately after putting the phone down or turning off the TV should be avoided. Activities like reading a book, journaling, or relaxation breathing before bed are highly recommended. Another recommendation is to get some sun exposure soon after waking for healthy circadian rhythm function.
https://academic.oup.com/sleep/article/45/11/zsac199/6674047