ferent clinical entities had in common. This scheme was not useful in the diagnosis and treatment of sick individuals. But it was useful in helping to understand where in the environment disease was coming from, and it was certainly helpful in directing prevention programs.”

We do not have an equivalent prevention-oriented classification scheme for the noninfectious diseases we are concerned about today, Dr. Syme maintained, and this issue is of particular importance in the social and behavioral sciences. “Many of the social risk factors we have identified are related not just to one or two clinical diseases but to a long list.” We need to study the ways in which these risk factors interact in “compromising the body’s defense systems rather than in causing specific diseases. We have been trained to study one clinical disease at a time from one disciplinary perspective, and this may be the reason why our search for risk factors to explain disease occurrence may be less than 100 percent successful.”

Unfortunately, he said, “the precise measurement of psychosocial factors is very difficult because the diseases we study are the end result of a very complex series of biological processes. Disease is a very distal consequence of the psychosocial factors under study.” But if we could “continue the progress that is now being made in studying such biological concepts as allostatic load or other similar intermediate disease processes, we might be able to improve this situation,” Dr. Syme said. “By studying the relationship of psychosocial factors to these more proximal outcomes, two important advances could be made. One advance is that we would have for the first time a disease-related yardstick to help define psychosocial variables more precisely.

“The second advance would be in moving closer to a more appropriate disease classification system. This would help us understand how certain social factors—poverty, social isolation, and particular types of job stress, for example—make people vulnerable to a variety of diseases. And it would help us to think in a way that is more oriented toward disease prevention. It would also provide a useful and efficient way to evaluate the effectiveness of interventions. Instead of having to wait five or 10 years for enough disease to develop in the intervened-upon group, we would be able to observe physiologic changes much sooner.”

Our tendency in the health sciences is to focus on individuals rather than the communities in which people live. “As has been demonstrated in many of the presentations at this symposium, we are making important progress in helping people change their behavior to lower their risk of dis-

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