I have condensation on the corner of a bedroom ceiling where the 2 outside walls meet. Condensation is only in the corner and doesn't happen unless the bedroom door is closed overnight and only in the colder weather. If the door is left open there is no condensation. Since my daughter prefers to sleep with the door closed I'm hoping to find a solution. Any suggestions are greatly appreciated.

You are probably missing the insulation in the ceiling at that area. Warm humid air hits the cold ceiling and condenses. You pretty much verify this by indicating it doesn't happen when the doors are open-it increases air flow and reduces the humidity. Check out the attic. Is there a cold air return in the room? If not, consider cutting an inch off the bottom of the door.

Thanks for the quick response. I'll try your suggestions.