Ecologic Models of Health
Causes and Effects
Beginning early in childhood, we observe causes and effects: a smile brings forth other smiles. Touch a hot stove and burn your fingers. We infer relationships: single cause, immediate effect. Lesson learned—maybe.
The inquisitive child may later attempt to find out if a quick tap with her hand on the stove has the same effect. She is learning something about dose and duration of exposure.
Multiple causal agents that contribute to health or disease outcomes make up a causal system. The system is made up of multiple causal relationships, each of which is a link or a thread in a causal web. Each link is important, potentially able to influence how the system as a whole behaves. These more numerous causal links are commonly depicted in graphic ecologic models showing the inter-relationships among the parts.
Ecologic models typically emphasize multi-level inter-relationships and emphasize dynamic interactions among them. Ecologic models make clear the systems nature of many complex problems, whether it’s cancer in an individual, cancer patterns in communities and populations, or other diseases and disorders.
Ecologic models try to account for dynamic feedback loops that act either to accelerate change or to dampen it.
Ecologic models try to account for dynamic feedback loops that act either to accelerate change or to dampen it. These loops are set into motion as system inputs and conditions change.
Some feedback loops help maintain system function, such as maintaining body temperature in a hot or cold environment, or a community response to natural disaster or disease outbreak. Other feedback loops derail the system profoundly, such illness that leads to unemployment, loss of home, poverty, and possibly further illness.
In a causal web, relatively minor changes can have magnified effects downstream.
In a causal web, relatively minor changes can have magnified effects downstream. Even a minor tweak—depending on what (and perhaps where and when) it is—can have multiple benefits or else multiple adverse impacts that cascade throughout much of the system. These are key leverage points. Finding and managing key leverage points can turn whole systems around.
An ecologic model and perspective—the "big picture"—should be valuable in helping someone decide how and where to intervene to improve system function within the context of their own interests, capacities and skills.
Written by Nancy Hepp, MS, and Ted Schettler, MD, MPH; most recent update on October 16, 2019.
- Science & Environmental Health Network's The Networker:
- 2019 Cancer and the Environment Symposium: Priorities for Research, Policy and Clinical Practice: Event Materials
- Laffall LD, Kripke ML. Reducing Environmental Cancer Risk: What We Can Do Now. President’s Cancer Panel. 2010.
- Field RW, Withers BL. Occupational and environmental causes of lung cancer. Clinics in Chest Medicine. 2012 Dec;33(4):681-703.
- Ted Schettler, MD, MPH, Science & Environmental Health Network: The Exposome and Cancer (presentation at the American Association for Cancer Research, June 2019)
- Cancer Treatment Centers of America: What are environmental risk factors, and how can I avoid them?
- J. Christopher States, Ming Ouyang and C. William Helm: Systems approach to identify environmental exposures contributing to organ-specific carcinogenesis
- The New School at Commonweal: Ted Schettler: The Ecology of Breast Cancer
- Ted Schettler, MD, MPH: The Ecology of Breast Cancer: The Promise of Prevention and the Hope for Healing
Enter your comments or questions below.
thank you for sharing with us this useful information