A long-standing theoretical tradition in clinical psychology and psychiatry sees deliberate self-harm , such as wrist-cutting, as “functional”—a means to avoid painful emotions, for example, or to elicit attention from others. There is substantial evidence that DSH serves these functions. Yet the specific links between self-harm and such functions remain obscure. Why don’t self-harmers use less destructive behaviors to blunt painful emotions or elicit attention? Economists and biologists have used game theory to show that, under certain circumstances, self-harmful behaviors by (...) economic agents and animals serve important strategic goals. In particular, “costly signals” can credibly reveal a “private state” in situations where verbal claims and other “cheap” signals might be disbelieved. Here, DSH is scrutinized using signaling theory, and a variant, the theory of bargaining with private information. The social contexts and associated features of DSH suggest that it might be a costly, and therefore credible, signal of need that compels social partners to respond. (shrink)