Observations Only Connect

Health care in a web

BMJ 2008; 336 doi: https://doi.org/10.1136/bmj.a452 (Published 26 June 2008) Cite this as: BMJ 2008;336:1468
  1. Nicholas A Christakis, professor of medical sociology, Harvard Medical School, and attending physician, Mt Auburn Hospital, Cambridge, Massachusetts
  1. christak{at}hcp.med.harvard.edu

The care we give one person can also have positive—or negative—consequences for the health of others around them

Consider an example: a factory making widgets pollutes the environment. This cost is borne by people who are downstream or downwind. The cost is not borne by the faraway consumers who purchase the widgets; nor is it reflected in the factory’s balance sheet. In social science parlance these costs are “externalities”—they are consequences that affect parties other than those engaged in a transaction.

Another example is this: you make an investment to improve your garden, and your neighbour not only enjoys a better view but also benefits because the value of his home rises. Strictly speaking, according to economic theory, you should tax your neighbour to recover some of the value you have created.

This idea of externalities can be extended to health and health care. The care we give to one patient can have adverse health consequences (negative externalities) but may also have beneficial health implications (positive externalities) for others to whom a patient is connected and …

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