Nocebos

From an interesting article about placebos and nocebos:

Although it is hard to imagine that nocebos would be purposely used in the practice of Western biomedicine, it is very likely that the nocebo effect is much more prevalent than either patients or physicians recognize. For example, when doctors highlight the potential side effects of new medications, such as GI distress or sexual dysfunction, patients complain of these much more frequently than when they are minimized. The same is true with pain caused by medical procedures: Women in labor who are given an epidural anesthetic are much more likely to report discomfort if the procedure is described beforehand as being more, rather than less, painful.

People are weird.