Why did you often have nightmares when you were a child?

My children often have nightmares, and we often read some books about this convenience, but we can't find the reason. It may be because the child is young, has poor psychological quality, or has some unsolved mysteries. Anyway, they don't have nightmares for no reason. I think you should take your children to the hospital to see if they are short of vitamins or trace elements.