Medical practice and malpractice litigation in an evolutionary context

We model the interactions between the behaviors of physicians and patients, subject to clinical and legal risks, by means of evolutionary game theory. We propose an original game in which patients may sue their physician for medical malpractice, and physicians have to choose between two alternative treatments, with different levels of benefits and risks. The safer treatment is also the less effective, therefore its provision corresponds, under the assumptions of our model, to practicing negative defensive medicine. We study the Nash equilibria, test their stability in the replicator dynamics, and analyze their welfare properties. We find that the accuracy of the judicial system plays an important role, with possible counter-intuitive effects related to legal reforms. If the court is not sufficiently accurate, defensive medicine can be favored, paradoxically, by an increase in the probability that defensive physicians are sanctioned by the court. A similar outcome can be generated also by an increase in the compensation paid to patients by physicians, when sanctioned for medical malpractice.