Commentary: describing differences--possibilities and pitfalls.

Reports of attempts to investigate, characterize, compare, and contrast those who are mentally ill fill the literature and invite controversy. It seems to be part of human nature to reestablish and define the differences between us. Creative descriptive studies continually challenge our perspective, yet they must be balanced with thoughtful consideration of possible selection bias, an understanding of how a perspective may influence a particular view, and an appreciation of statistical constraints, before describing differences as predictive risk factors.