Ideas

Public health problems are shaped by interconnected conditions, not simple chains of cause and effect. This post explains why upstream thinking is useful but incomplete, and how systems thinking can help practitioners, funders, and evaluators map relationships, identify opportunities for change, anticipate consequences, coordinate across sectors, and track early signals of progress.

For a long time, public health programs focused on changing people’s awareness, knowledge, and behavior. The thinking was that if people knew more about their health and made better choices, their health would improve.

Over time, the field has increasingly recognized that health is shaped by much more than individual choices. Where people live, the educational and economic opportunities available to them, the quality and stability of their housing, and their access to resources and support all affect their ability to be healthy. These conditions are known as the social determinants of health. Public health practitioners now ask what individuals need to do differently, and also what must change in the conditions and systems around them to support health.

A metaphor that has helped direct our attention is that of “upstream thinking.”

It comes from a parable often attributed to Irving Zola and popularized by John McKinlay in a paper originally published in 1975 (McKinlay, 2005). In the story, rescuers keep pulling drowning people out of a river. They are so busy saving people that no one has time to walk upstream to find out why people keep falling in.

The lesson is simple and compelling. Instead of only responding to health problems after they occur, we should address the root causes.

Metaphors can shape how we understand problems and what we decide to do about them. Upstream thinking helped public health recognize the importance of looking beyond individual behavior.

But as public health increasingly embraces systems change, is the metaphor still serving us well? It encourages us to look for the source of a problem, but it does not necessarily help us understand how many conditions affecting health interact and change over time. Think about the picture the metaphor leaves behind. There is a river, a source, and water flowing in one direction. Find the problem at the source, fix it, and the benefits will flow downstream. This reinforces the idea that causes and consequences follow a relatively straight path.

Health doesn’t work that way. The development of health over a lifetime is ongoing, dynamic, and cumulative. Health is influenced by our continuous exposures, experiences, and interactions — all shaped by the places we live, learn, work, and play. These include income, education, housing, employment, neighborhood conditions, transportation, and social relationships. Geography, discrimination, and unequal access to resources and decisionmaking power influence these conditions, creating advantages for some communities while placing additional barriers in front of others.

These conditions are also interconnected. They influence one another, often in both directions, and their relationships change over time. As a result, their effects on health aren’t simple or predictable.

For example, access to quality education can influence employment and income, which can affect health. But health can also shape educational and employment opportunities. Similarly, stable housing can support success in school and work, while changes in employment can threaten housing stability. These factors are interconnected, and the conditions that shape access to them can either create opportunities or reinforce barriers to good health.

There is no single starting point or endpoint in a system. Conditions continually influence one another, making it difficult to identify any one place as truly upstream. Yet the upstream metaphor risks oversimplifying the very systems we are trying to change.

Nancy Krieger made a similar argument in her 2008 paper in which she proposed to “banish the terms proximal and distal from the public health lexicon and refer instead explicitly to levels, pathways, and power, as one small but needed step toward developing better thinking and strategies for leveling health inequities.” She asserted, “Clear action requires clear thinking (Krieger, 2008).”

Change Is Continual

We want change. We develop programs, build partnerships, advocate for policies, and invest resources because we want conditions to improve.

But what happens after the change we wanted actually occurs?

A new policy may improve access to health care services while increasing demand beyond what providers can accommodate. A new funding opportunity may strengthen one organization while unintentionally drawing staff and resources away from others. An intervention may work well initially but become less effective as circumstances change.

Change can create opportunities. It can also create new challenges.

A system is made up of interconnected parts that influence one another. When something changes in one area, it can create ripple effects across others, sometimes in unexpected ways. Understanding these connections is important for systems change because focusing on one issue without considering its relationship to others can lead to missed opportunities, unintended consequences, or solutions that fail to address the underlying problem.

And systems are never standing still. This may sound obvious, but it has important implications for how we approach public health.

A systems approach asks us to consider both the challenge and the opportunity. Rather than assuming that fixing a root cause will resolve a health problem, it asks: What else might change as a result? And how might those changes influence what happens next?

Start With What Is

If we want to change something in a system, we first need to understand how that system works. That means looking at the conditions that exist, how they relate to one another, and how those relationships are changing. It also means understanding whose experiences are reflected in our picture of the system, whose are missing, and who has the power to shape it.

We can never understand every aspect of a system, but we can develop a clearer picture of how it works to help us make thoughtful choices about what to change, learn from what happens, and adjust our strategies as conditions change.

Understanding these relationships helps us ask better questions. The connection between education and health illustrates why: each can shape the other, and the strength and direction of that relationship vary with the conditions surrounding individuals and communities.

Education can open doors to better-paying jobs, greater financial security, and access to health insurance. It can also help people navigate healthcare. Schools themselves can provide health knowledge, supportive relationships, and access to services. However, the extent to which these opportunities lead to better health depends on other factors, including housing stability and employment opportunities.

At the same time, health can shape educational experiences. For example, a child experiencing chronic illness or untreated mental health challenges may struggle to attend school, while unstable housing or limited access to healthcare can make these challenges worse. However, access to healthcare, supportive schools, and community resources can help reduce these barriers. Over time, these interconnected conditions can influence educational attainment, employment, income, and future health, showing how changes in one area can affect outcomes across others.

These relationships also depend on context. Education may not lead to economic security when good jobs are scarce or discrimination limits opportunities. Having health insurance may not translate into receiving care when providers are unavailable or services remain unaffordable.

A systems map can make these connections easier. Think of it as a visual picture of how different factors, such as health, education, housing, and employment, are connected. Lines or arrows show how changes in one area may influence others, helping us see how relationships can create opportunities, reinforce barriers, or lead to unintended consequences. While a systems map cannot capture every aspect of reality, it can help us recognize what we might otherwise overlook and better understand where changes could make a difference.

Takeaway: Develop a shared understanding of the system to make relationships visible, using tools such as systems maps.

Find Where Change Can Take Hold

Once we have a clearer picture of the system, the next question is where to act in order to make a difference in health. Simply identifying education as an upstream determinant doesn’t tell us where or how to intervene.

A systems map can highlight places to act based on the anticipated effects a change could have. This can lead to more informed decisions about where to focus our efforts and identify leverage points, or places where a change could have effects beyond its immediate purpose. The following questions can help explore these opportunities.

• Where are people organizing around a shared concern?
• Where are organizations beginning to work differently?
• Where are resources available?
• Who has the power to make decisions, and who is seeking to change those decisions?
• Where are several developments coming together to create an opportunity?

There is an important distinction between where change could have the greatest effect and where change is possible right now. A particular relationship or practice may be a powerful place to intervene, but the resources, relationships, or political conditions needed to change it may not exist yet. Systems thinking asks us to consider both the potential impact of an intervention and the conditions that make it possible.

A systems map can make relationships and feedback visible. A stakeholder or power map (see the Othering and Belonging Institute toolkit) can help us understand who influences decisions, whose voices are missing, and where relationships could be strengthened. Neither map gives us a definitive answer, but using both together can highlight possibilities that might otherwise be overlooked and inform how to move forward.

There may be no single best place to begin. At any given moment, different parts of a system may offer different opportunities for change.
A relatively small action in the right circumstances can lead to much larger changes. But the same interconnectedness means that an intervention can produce unintended consequences or fail to last.

Before acting, we need to ask not only whether change is possible, but what it might set in motion: Will the people and organizations involved have the capacity to respond? What might reinforce the change? What might work against it?

And because the system will keep changing, we need to continue asking these questions in real time as the work unfolds. Consider a campaign encouraging people to seek mental health services. If successful, more people reach out for support. But what happens if providers cannot meet the increased demand? Longer wait times could discourage people from seeking care, potentially undermining the original goal. It could also lead to burnout among the existing providers who try to meet the increased demand. Understanding these connections before and during implementation allows us to anticipate challenges and adapt strategies.

Takeaway: Look for places where change could have a wider impact and where conditions make action possible.

Policy Is Not the Only Way to Transform a System

When public health talks about structural change, policy change often takes center stage, and for good reasons. Policies can influence how resources are distributed, who has access to opportunities, and which conditions are sustained. But policy change can take years, and opportunities may depend on political conditions. Meanwhile, other parts of a system may be more open to change right now.

Systems operate through relationships, organizational practices, decisionmaking processes, and the ways information and resources flow among people and institutions. They are also shaped by people’s mindsets and mental models: the assumptions and beliefs people hold about how things work, what causes problems, and what solutions are possible. These assumptions, including unconscious biases, influence the decisions people make.

Changing any of these can alter how a system functions. For example, a health department, school district, and community organization might initially view chronic student absenteeism as a problem of family motivation. After sharing data and listening to families, they may recognize that transportation barriers, untreated health needs, unstable housing, and inflexible service systems are interacting to keep students out of school. Their mental model shifts from “families need to try harder” to “our systems need to work together differently.”

That shift can change who participates in decisions and which solutions are considered. Instead of relying only on attendance reminders, the partners might coordinate transportation, health care, and family-support services; share information more effectively; and involve families in shaping the response. No single policy or program has to change for the system to begin functioning differently.

The question becomes: What can we change in how this system works? Not simply: What policy needs to change?

Takeaway: Look for places where meaningful change is possible by shifting practices, relationships, and ways of thinking.

The Silo Problem

There is another challenge to thinking in systems. We often organize our work in ways that divide them. Funding is largely organized by sector. Health, education, housing, and economic development typically have their own funding streams, priorities, programs, and measures of success. Yet the people and communities these sectors serve don’t experience their lives in separate categories.

An investment in housing stability may improve school attendance and health. Better access to mental health care may support educational achievement and employment. Changes in transportation may affect access to all three. But when each sector measures only its own outcomes, we may miss these connections. We may also overlook unintended consequences in other parts of the system.

What would happen if funders and practitioners across sectors began with a shared understanding of the conditions they want to change? They could identify relationships across their areas of work, consider where coordinated action might make a difference, and agree on indicators that reflect progress toward shared goals.

Some of those indicators might measure changes in health, education, or housing. Others might capture changes in the system itself that are beneficial across sectors: Are new relationships forming? Is trust growing? Are community members gaining influence over decisions? Are organizations sharing information and resources differently? Is funding beginning to support shared priorities?

These may be early signals that the system is changing, even before population-level outcomes improve. This recognizes that the relationships among sectors are themselves part of the system we are trying to change.

Evaluation can help document these incremental changes as they occur, showing how relationships, coordination, and decisionmaking are evolving. What relationships changed? What new opportunities or barriers emerged? Were there unintended consequences? Did the intervention change how people and organizations understand the problem? These questions can help us learn whether an intervention worked as well as how change is unfolding and what we might need to do next.

Takeaway: Work across sectors to identify shared opportunities for change and measure progress toward common goals.

What could we do differently?

Moving from upstream thinking to systems thinking doesn’t abandon our commitment to addressing structural conditions. It changes how we understand those conditions and how we act on them. It resists the temptation to begin with a preferred solution. Instead, we need to understand the system, identify where change may be possible, and choose strategies that fit the circumstances, knowing that we may need to adjust them as the system responds.

Here are a few ways to begin:

• See the whole system. Look for relationships, not just root causes. Look beyond a single health issue or determinant to understand the relationships that shape it. Pay attention to how conditions influence one another in different directions.
• Look for places where people, resources, relationships, and opportunities are coming together. Consider where action may be possible right now.
• Plan for feedback and unintended consequences. Use systems maps and learn from the people who experience the system to explore how a proposed intervention might affect other parts, including unintended consequences.
• Look beyond policy. Consider opportunities to change relationships, organizational practices, decisionmaking power, information flows, and shared goals.
• Identify opportunities to work with multiple sectors. Support coordinated action and, where feasible, shared or aligned funding that recognizes how health, education, housing, and other conditions interact.
• Measure early signals in the system, not only final outcomes. Track early signals such as new relationships, shifts in decisionmaking power, changes in resource flows, and growing capacity to act together. Recognize the contributions of multiple partners rather than attributing complex outcomes to a single intervention.

The upstream metaphor gave public health an important message. Look beyond the immediate problem to understand what is causing it. We needed that lesson.

A systems approach takes us a step further. It asks us to see that causes and consequences are connected, that change moves in many directions, and that the conditions we are trying to improve are themselves continually changing.

Perhaps the more useful question is no longer simply: How far upstream should we go?

Perhaps it is: How is this system working, and where can we help it change?

At Community Science, systems thinking is central to how we approach our work. Explore more of our thinking and how we apply systems thinking in the related blogs below.

Five Principles for Improved Systems Thinking

A Systems Approach to Organizational Assessment and Evaluation

It’s All About Community, Systems, and Justice

“Signals of Change” – What Are They, Why Are They Important, and How Do You Get Started?

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About the Author

Questions this post answers:

• What are the limitations of the upstream metaphor in public health?
• How does systems thinking change the way we understand health inequities?
• How can systems maps help identify opportunities for intervention?
• Why do public health interventions produce unintended consequences?
• How can public health systems change without a new policy?
• What should evaluators measure while systems are changing?