I have solitare diamond earrings with screwbacks and I take them out at night...I sleep on my side and they jab into my head! lol! But I do have small hoops with diamonds and they don't bother me at all when I sleep in them.
Mine are 2 ctw diamond studs with screw backs and the posts also go into my head when I when I sleep on my side. It might depends on the particular earrings and each person's ears too. My ear lobes are very small and close to my head so that might make a difference. But, when I was very young I always slept with my tiny studs on and they didnt bother me at all....I also sleep with my Rolex a lot and it doesnt bother me at all, while some people find it uncomfortable...