Nightmares when going to bed early

I was talking to my friend and she told me that i should look into this, so i guess thats why i am here.So my problem is every time i try to go to bed before 12am i have some type of nightmare and i will wake up in a half and hr to a hr later.Then i wont be able to get back to sleep for the rest of the night, but if i stay up late and go to bad after 12am i have no nightmares at all, so would anyone know the reason to this.

Thanks Ryne

It's probably related to the sleep cycle and the stages of sleep. When you go to bed late it probably effects your stress level and hormones.