The only way for a parent to know which is happening to their child is... is the child aware you are there?
With a nightmare, the child wakes up and is looking for you for comfort. When you walk in the room, they see you and want to be with you. You calm them down, they go back to sleep.
With a night terror, the child never wakes up. She may be sitting up in bed, her eyes may be open, she may be screaming but when you walk in the room she doesn't see you and doesn't turn to you for comfort. This should be treated like sleep-walking - you stay nearby to make sure she doesn't hurt herself, you can softly say things like "it's ok, mommy's here" but you shouldn't wake her. Eventually, she will lay down and go back to full sleep.
No one really knows what causes either. Stress, being overtired, and eating too big a dinner to close to bedtime have been linked to both.
at 12:37 AM on Jan. 24, 2009