The Ecology of defensive medicine and malpractice litigation

We analyse the relations between defensive medicine and medical malpractice litigation by an evolutionary game between physicians and patients. When medical treatment fails, patients may suit the physician and seek compensation. Conversely, physicians may prevent negligence charges by practising defensive medicine. We study the population dynamics and find the Nash equilibria and their Pareto-ranking. Furthermore, we show that, when the mixed-strategy equilibrium exists, then the shares of defensive physicians and litigious patients exhibit time-evolution paths similar to prey-predator relations in the Lotka-Volterra model, in which physicians can be seen as preys and litigious patients as their predators. Then, defensive physicians can be seen as adapted preys who improved their Darwinian fitness through mutation. The increase in adapted preys (i.e.defensive physicians) decreases predators’ fitness leading to a decrease in predators (i.e.litigious patients). In this context, we show that perfect cooperation with neither defensive physicians nor litigious patients can be the social first best. Our results may explain heterogeneous findings in empirical literature on these phenomena.