The origin of anxiety disorders - an evolutionary approach.

There is growing interest in the application of evolutionary theory to medicine. In this review, we outline an evolutionary approach to the anxiety disorders. We begin by considering the nature of fear and anxiety, and their evolutionary benefits. We emphasize that fear and anxiety exist in multiple organisms, and note the implications of brain complexity in Homo sapiens for the anxiety disorders. This account emphasizes the importance of distance from a threat; in H. sapiens, it is possible to experience fear and anxiety even when threats are temporally and spatially distant.