Systems thinking in public health

Systems thinking is an important approach in public health. Using systems thinking can help us understand health and social problems more clearly. As a result, it can help us find better solutions.

Using systems thinking in public health can help us:

  • Identify and address the root causes of public health problems or challenges and why they persist
  • Identify where we can focus our efforts to have the greatest positive impact
  • Develop more effective and adaptable programs and policies
  • Predict and prepare for unintended consequences of change
  • Avoid accidentally making things worse
  • Achieve more effective and longer-lasting outcomes

In a nutshell, this is because systems thinking involves stepping back and looking at how all the pieces of a system interact in order to understand the big picture.

This post covers some important concepts to help you understand why and how systems thinking is so beneficial in public health.

Estimated reading time: 13 minutes

Systems in public health

Working in public health, we are surrounded by systems. Possibly, the most obvious one is the health system. Some other important systems include:

  • Populations
  • Communities
  • Government
  • Social services and welfare systems
  • Hospitals

Some of these sit entirely within the health system. Others overlap or interact with it. Some are set up for a clear purpose, others simply develop naturally over time.

So, what exactly do we mean when we say that something is a system?

What is a system?

A system isn’t just any old collection of things. A system is an interconnected set of elements that is coherently organized in a way that achieves something.

— Donella H. Meadows in Thinking in Systems: A Primer

A system is a whole made up of a group of separate parts that:

  • Are joined, related, and connected to each other AND
  • Together, create patterns of behaviours or actions AND
  • Are organised in a way that achieves something

The health system, for example, is made up of organisations, people, technologies, tools, medicines, money … All these things interacting and influencing each other in some way or another in a combined effort to promote and maintain health.

What are the features of systems?

Is there anything that is not a system? Yes — a conglomeration without any particular interconnections or function. Sand scattered on a road by happenstance is not, itself, a system. You can add sand or take away sand and you still have just sand on the road. Arbitrarily add or take away football players, or pieces of your digestive system, and you quickly no longer have the same system.

— Donella H. Meadows in Thinking in Systems: A Primer

All systems have the following three features:

  • Elements: the parts that go together to form the whole
  • Interconnections: the way the elements are joined, related, and connected to each other
  • Outcome: how the system behaves or whatever the system achieves

A system will change (or break) if you:

  • Take away, change, or add any of the features or
  • Change the way they are put together


Elements are the building blocks of the system. One way of thinking about elements is to split them into 3 types:

  • Stocks
  • Flows
  • Feedback loops

Stocks are the things we can see, touch, feel, or measure. These include physical things like hospitals, people, medicine, and money. They also include intangible things, like knowledge, skills, and experience.


Flows represent the changes to the stocks — things ‘flowing’ in and out of the system. Births and deaths, for example, change the number of people in the system. (Incidentally, death also removes knowledge and experience.) Income and spending change the amount of money available.

Feedback loops

Sometimes changes to a stock affect the flows in or out of it.

For example, within a population, new births mean more people. More people can grow up to have more babies, which means even more people. And then they grow up and have even more babies.

When this happens, it is called a feedback loop.

Reinforcing (or positive) feedback loops

The births = more people = more births = more people loop is an example of a reinforcing feedback loop. This means that the feedback loop enhances the direction of change. This type of feedback loop is sometimes also called a positive feedback loop.

Left unchecked, reinforcing feedback loops will often create havoc in the system.

Balancing (or negative) feedback loops

There are also feedback loops that work against the direction of change. These are called balancing (or negative) feedback loops. Balancing feedback loops are much more common than reinforcing feedback loops.

In the same way that births create a reinforcing feedback loop when it comes to population, deaths create a balancing feedback loop. That is to say, when there are more people, there are more people who eventually die. Then there are fewer people. When there are fewer people, there are also fewer deaths.

Feedback loops and lag time

The birth, life, and death feedback loop examples lead nicely to an important thing to remember about feedback loops. This is that they don’t necessarily take effect immediately.

More babies may eventually lead to even more babies, but it takes quite a few years before a baby is old enough to make more babies. It (hopefully) takes quite a few more years after that before they die.

This lag time is quite important in systems thinking, as it can help us predict how long it might take for our actions to have an impact.


The second feature that all systems have is interconnections. We said before that interconnections are the way the elements are joined, related, and connected to each other.

Interconnections include everything from literal, physical connections to the underlying norms and forces that drive the way the system’s elements behave.

In a health system, for example, you have formal and informal referral pathways and interagency and community networks that connect different services and organisations.

Risk factors and determinants of health are interconnections between people, their living circumstances, and their health.

Things like laws and social and cultural norms are also interconnections that strongly influence the way a health system works in a particular time and place.

A system’s interconnections are very important because they drive how the system works.


The last feature of all systems is its outcome*. This is the system’s defining and most important feature.

It is what interconnections of the system’s elements actually achieve.

In the case of human-made systems, we can set them up and define their purpose (or purposes). This can have an enormous impact on both the system’s interconnections and its elements.

For example, the purpose of a hospital may be to provide medical care to children. What would happen if its purpose changed to provide psychiatric care to adults with severe mental illness? The hospital would need new staff with different specialisations. They would need new equipment and medications (elements), new guidelines and intake procedures (interconnections). If it is a private hospital, another purpose may be to make money. This would mean a whole range of resources (elements) and procedures and policies (interconnections) that would differ from those in a public hospital.

However, just because we define a purpose doesn’t mean that the purpose we define will be the outcome.

For example, even though the purpose of the health system is to improve health by providing equitable, high-quality health care that everyone can access, this is not the outcome in reality. Not every actor in the health system focuses on doing that. There are other factors at play, such as profits, politics, laws, moralities, and even differing concepts of what health means.

* A note on terminology

In information about systems thinking, you will probably see this called the ‘purpose’ or the ‘function’. We have intentionally chosen not to use these terms because:

  • To know the ‘purpose’ or ‘function’ of a system, we need to look at what the outcome of the system actually is
  • This may or may not align with what we think the purpose is
  • Some systems are set up with an intention (such as the health system)
  • Not all systems have a planned purpose (such as the ecosystem)

Furthermore, the word ‘purpose’ inadvertently implies that every system has an agreed, single purpose. It also makes it too easy to think of the system’s outcome as what we think the system should do instead of what it actually does.

Finally, we chose not to use the word ‘function’ to avoid confusion because we already use the word function across this site to refer to the W3 Functions.

Understanding systems

As we have seen, a system is more than just a collection of parts. It is the product of the interactions between all of its parts.

So, if we want to understand a system, how do we go about it? That is where systems thinking comes in.

Systems thinking in public health

What is systems thinking?

[Systems thinking] is the opposite of [scientific] reductionism, taking everything apart and looking at the pieces. Systems [thinking] is putting everything together and looking at the whole and how things interact.

— Donella Meadows

We are often taught the easiest way to learn about something big is to break it down into smaller parts. But to understand a system properly, we need to look at how the whole thing works when all the parts are put together. This is the essence of systems thinking.

Systems thinking is about looking at the whole system — all the elements, flows, feedback loops, cycles, patterns, behaviours, and functions — as a single entity. It is looking for how changes in one part of the system impact the entire system.

Examples of systems thinking in public health

If we just tell people smoking causes cancer, they’ll stop smoking, right..?

To illustrate, let’s look at a something a lot of health systems are trying to tackle: lung cancer and smoking. Systems thinking is about more than just saying: ‘Smoking causes cancer. We can tell people that and then they’ll stop smoking. Problem solved.’

Systems thinking compels us to look for all the different things that influence different people in different times and places. It’s about trying to understand how these things work together to make some people more or less likely to try smoking and to keep smoking.

It leads us to ask, why do people smoke? Is it cultural? Could it be peer pressure? Is there too much advertising? Is it because tobacco is so cheap and widely available? Are some combinations of these things stronger influences than others?

Later, when we have a big picture that we’ve created from as many points of view as possible, we can start to look for the places where we can try to make positive changes. Can we make smoking less attractive? Can we make it easier for people to quit if and when they want to?

Systems thinking also leads us to look for unintended consequences of our actions. For example, if we make cigarettes more expensive, people might be less likely to buy them, but what else might happen? Could it impact people who don’t want to quit or who struggle to quit and who have little money? What can we do to prevent causing harm to people who might suddenly need to make a choice between buying cigarettes and buying food — between involuntary nicotine withdrawal or hunger?

What works and why in peer-led responses to HIV and Hepatitis C?

Stage 1 of the W3 Project is a real-life example of systems thinking in public health. This project used systems thinking to build a picture of how peer-led programs and organisations create positive change in their communities and in the health sector and policy environment. The result was a systems map that can be used to help understand, demonstrate, and improve the impact of peer work in public health: the W3 Framework.

When should we use systems thinking?

A drawing of six blind men gathered around an elephant. Each man is touching a different part of the elephant's body. The first is touching the trunk and imagining a snake. The second is touching an ear and imagining a rug. The third is touching a tusk and imagining a spear. The fourth is touching a leg and imagining a tree. The fifth is touching the side of the stomach and imagining a wall. The sixth is touching the tail and imagining a rope. By just looking at one part of the elephant, each man has an incomplete idea of what an elephant is like. None of them are wrong. But none of them has the whole picture. It illustrates that you can’t understand what an elephant is if you just look at the different parts of it — just like in systems thinking.

Systems thinking will help us any time we are working with a system and we need to understand the bigger picture.

However, systems thinking is of utmost importance when we face any kind of complex system or wicked problem.

Complex systems

Complex systems have elements with memory that can learn and adapt their behaviours and interactions over time. These systems interact, adapt, and co-evolve with other systems. As a result, the processes, patterns, and behaviours of complex systems are dynamic and unpredictable. Complex systems tend to seek balance and respond to changes in a way that counteracts them.

An example of this is a community. The people — individuals, family networks, social networks, workplaces — all grow and change over time in response to changes in their environment. The way a community responds to change will not be exactly the same more than once. It will have learned and grown from previous times it responded to change.

It is simply not possible to understand complex systems properly by breaking them down and looking at their parts in isolation. We need to look at the big picture in order to figure out how it adapts and evolves in response to changes.

Wicked problems

If a complex system has a problem, it is probably not a simple one with an easy fix. More likely, it is what we call a wicked problem. These are problems that:

  • Are not completely or well understood because we only have incomplete, contradictory, or contested information
  • Involve many different interacting actors (and types of actor) with competing or conflicting priorities
  • Overlap with, are the symptoms of, or contribute to, other wicked problems
  • Can’t be solved with a single solution

Almost all (if not all) challenges in public health are wicked problems. This is why systems thinking is so important in public health.

Conclusion: Public health needs systems thinking

Population health is a product of dynamic interrelated mechanisms. Most health researchers implicitly or explicitly consider this complexity in formulating specific study hypotheses. (…) Engaging with systems science principles can help investigators do the best science and identify the best interventions to protect population health.

— Stephen J. Mooney in ‘Systems thinking in population health research and policy’ from Abdulrahman M. El-Sayed & Sandro Galea’s Systems Science and Population Health

Anyone working in any area of health is working in an enormous, complex system. Almost without fail, the health problems facing society are wicked problems without simple solutions. Without systems thinking, we will struggle to understand these problems, let alone make any headway in trying to solve them. Systems thinking is our best chance to help communities achieve their best possible health.

Further reading and resources

Want to read more about systems thinking? Check out some of the resources below.

Sources used to write this post

Further reading

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