It does depend on why this is happening. It could be just to much moisture when showering. If it's just a crack and if you don't want it to come back then I would mud and tape it. Caulking it will only last for so long. If it's like paint pealing then scrape it off and prime it and then mud it and then sand it and then prime it and then paint it.
Depends on what's causing it. If it more or less a straight line, that's a separation in the drywall. I would caulk the crack and repaint. If it comes back, might be ceiling joists settling.
Make sure you buy paint for bathrooms.
Spackle and repaint
Thanks! Your answer is awaiting moderation.