Symptoms of illness are not inevitably tied to an underlying disease --rather, many organisms, including humans, adapt their symptom expression to suit their needs. That's the finding of Arizona State University's Leonid Tiokhin, whose research appears in the Quarterly Review of Biology.
Tiokhin, an anthropology doctoral candidate in the School of Human Evolution and Social Change, uses evolutionary theory to understand human behavior and psychology, and is especially interested in the evolution of communication. His article, "Do Symptoms of Illness Serve Signaling Functions? (Hint: Yes)," argues that changing symptom expression to alter others' behavior can be beneficial in several different ways. For example, feigning or exaggerating symptoms of illness can cause an individual to receive extra aid and social support from others, or can prevent unwanted others from interacting with them.
Alternatively, suppressing symptoms of illness can prevent exploitation by those who prey on the weak, as well as prevent avoidance by potential mates. In some cases, it can even benefit organisms to self-induce illness, actually causing pathology, if the costs they pay to do so are outweighed by the social benefits.
Tiokhin's key contribution is his development of a comprehensive conceptual framework for understanding how, when and why symptoms have signaling functions. In doing so, he suggests that signaling theory can shed light on some longstanding puzzles in the medical field, such as how symptoms can exist without disease and why symptom severity fluctuates in different contexts.