The Limits of Reductionism in Medicine: Could Systems Biology Offer an Alternative?

This is the fi rst in a series of two articles that look at the lessons for clinical medicine from systems biology. S ince Descartes and the Renaissance, science, including medicine, has taken a distinct path in its analytical evaluation of the natural world [1,2]. This approach can be described as one of " divide and conquer, " and it is rooted in the assumption that complex problems are solvable by dividing them into smaller, simpler, and thus more tractable units. Because the processes are " reduced " into more basic units, this approach has been termed " reductionism " and has been the predominant paradigm of science over the past two centuries. Reductionism pervades the medical sciences and affects the way we diagnose, treat, and prevent diseases. While it has been responsible for tremendous successes in modern medicine, there are limits to reductionism, and an alternative explanation must be sought to complement it. The alternative explanation that has received much recent attention, due to systems biology, is the systems perspective (Table 1). Rather than dividing a complex problem into its component parts, the systems perspective appreciates the holistic and composite characteristics of a problem and evaluates the problem with the use of computational and mathematical tools. The systems perspective is rooted in the assumption that the forest cannot be explained by studying the trees individually. In order for a systems perspective to be fully appreciated, however, we must fi rst recognize the reductionist nature of medical science and understand its limitations. For this reason, the fi rst article in this series is dedicated to examining the reductionist approach that pervades medicine and to explaining how a systems approach (as advocated by systems biology) may complement it. In the second article, we aim to provide a more practical discussion of how a systems approach would affect clinical medicine. We hope that these discussions can stimulate further inquiry into the clinical implications of systems principles. While the implementation of clinical medicine is systems-oriented, the science of clinical medicine is fundamentally reductionist. This is shown in four prominent practices in medicine: (1) the focus on a singular, dominant factor, (2) emphasis on homeostasis, (3) inexact risk modifi cation, and (4) additive treatments. Focus on a singular factor. When the human body is viewed as a collection of components, the natural inclination of medicine is to isolate the single factor that is most …