Okay, so here’s the understatement of the century: people are…complicated.

Like, when the American poet Walt Whitman famously wrote, “I contain multitudes,” he was definitely being poetic, but he was probably mostly saying something along the lines of “I really don’t have time to get into how complex I am right now, okay?!” But, unfortunately, public health experts don’t have that luxury. To do their job, they need to know who’s healthy, who’s not, and most importantly, why.

Our identities, societies, and health are all mixed together in a cool, weird, and often deeply unfair way–thanks in large part to the social determinants of health that we covered last episode. Experts are still striving to understand it all. But lucky for us, at Crash Course, we’re pretty much in the business of striving to understand stuff–and we don’t back down from a challenge!

So today, we’re going to go beyond the basics and look at exactly how society “hacks” into our bodies and affects our health–and why it affects each of us differently. ​​Hi, I’m Vanessa Hill. And welcome to Crash Course Public Health! INTRO The social determinants of health are the conditions of our societies that influence our health.

These include things like our income, housing, and education that can affect us on a biological level. This is because as living organisms, we need…stuff. You know: food, oxygen, even YouTube videos.

Stuff! These are resources that we extract from our surroundings and use to make ourselves, like, not dead. Or, in the case of YouTube videos, not bored.

For a lot of us, when we hear the word “resource,” one of the first things that comes to mind is probably money. Like we mentioned last time, having access to money is a pretty big deal for our health. More money can translate into more medical services, access to healthier foods, and better housing.

But if we stretch our definition of “resource” just a bit, another resource we can think about in the context of our health is knowledge. In this case, we’re not talking about memorizing country capitals or who started the War of 1812. We’re talking about knowledge about our health–or health literacy.

To be health literate, we don’t need to be a doctor. We just want to have the ability to locate, recognize, and use basic medical information and services. If our health were a foreign language, we’d basically just want to know enough to be able to ask where the nearest bathroom is and be able to get ourselves there to use it.

The other piece of our health literacy is knowing how to navigate our health care system. For a lot of us, the health care system may seem like a labyrinth of paperwork and expenses that can feel impossible to figure out. Things like knowing the difference between an emergency room and urgent care and when to go to which one are basic questions that can feel hard to navigate.

So while health literacy might help us identify if we’re sick, knowledge of our particular health care system might help us find a doctor who specializes in our particular kind of sickness. Together, money and knowledge are a major part of another resource that is pretty central to our health: autonomy, or how much control we have over our life. People who report feeling less in control of things like their income, occupation, and daily schedule typically are also more likely to smoke, have higher blood pressure, and have less time to exercise, all which are correlated with worse health outcomes.

And feeling less in control of things might lead to something we’ve all felt from time to time: stress. Whether we’re anxious about giving a speech at our brother’s wedding or worried that we didn’t exactly crush that biology exam yesterday, life is full of stressful moments that leave our heads aching, our hearts racing, and our bodies feeling…[indistinct groan]. But as it turns out, having these anxieties simmering on the backburner of our brains literally all the time can be more than just stressful.

It can be detrimental to our health. Stress can literally make our bodies age faster, which now that I know that also kind of stresses me out, and oh god here comes that dread… Now, don’t get me wrong. Some stress can actually be useful.

Like early in human history, the stress of potentially being eaten by the local pride of lions told us to leave them alone. And the added stress of fighting off a virus is also a big part of how our immune system learns how to fight diseases and improve itself for the next time it encounters that virus. But when stress becomes frequent, or chronic, it can start to add up and take a toll on our health..

And for some groups of people, the amount of chronic stress they experience, often through long-term issues like discrimination and marginalization, is so large that scientists can actually detect noticeable differences in the group’s health outcomes. In the early 1990s, the American public health professor Dr. Arline Geronimus was researching the factors that affected women’s fertility when she noticed something strange.

Data showed that for white women, the age range associated with high fertility, healthy pregnancy and lower risk of infant death was generally somewhere between 20 and 30. However, for Black women, that age range was generally in their teens. Geronimus hypothesized that because of the stressful social, economic, and environmental factors that Black women face as a result of systemic racism, their bodies are literally aging faster than the average white woman.

Dr. Geronimus called this “weathering.” Let’s go to the Thought Bubble to see what it means for our health. You may know of weathering as the thing that happens to rock formations when things like wind and rain break them down over time.

Except in this case, the thing that’s being worn down is our body. And the thing doing the wearing down is stress, which can be a consequence of, and compounded by factors like racism. Stress might not seem like something that we can get real science-y about.

Like, we measure the distance between galaxies in light-years, we measure bananas in bunches, and for me at least, I just kind of measure stress by how much I want to scream or crawl back into bed. While it’s not like stressful experience leave behind little stress particles that we can count, it turns out scientists can track the history of stress in our bodies. To do this, they use a measurement called our allostatic load.

Which, now I say it out loud, sounds like a pretty great band name! Our allostatic load is basically the measurable wear and tear that our body goes through when it’s under severe or chronic stress. There are certain biological processes associated with stress, like increases in heart rate or spikes in a stress hormone called cortisol.

When these things happen repeatedly for a long time, they can leave behind distinct biological markers that we can measure. This includes things like cholesterol levels and changes in our hormone patterns that may negatively affect our health. Allostatic load is like our body’s very own stress-fossil!

Thanks, Thought Bubble! Now, we may think of stress as a very adulty phenomenon. We get stressed about things like paying bills or sitting in traffic.

But for some people, stress can literally begin at birth. Adverse childhood experiences, or ACEs, are potentially traumatic events that occur in childhood as we grow up. These events can include things like food insecurity, domestic violence, or living in a home with someone struggling with drug misuse or mental illness.

And experiencing four or more ACEs has been associated with increased risks for things like cancer, diabetes, and suicide. That’s because dealing with so many ACEs can be pretty darn stressful–and things like racism and systemic inequality only make this stress more severe. But public health experts don’t have some algorithm or magic converter that lets them plug in all of our stressy social determinants of health and come up with crystal clear predictions for our health future.

Because humans are, like, kind of complicated! I mean, if people are good at one thing, it’s being a whole bunch of different things. Take our identities, which includes factors like our race, class, gender, and sexual orientation– just to name a few.

It should come as no surprise then, that humans occupy several different identities at once. Those different combinations, and the way our larger society views them, affect us differently. To help put this in perspective, we can consider the concept of intersectionality.

The term was coined by American law professor and civil rights activist Kimberlé Crenshaw in the late ‘80s to explain why theories of sexual discrimination and racial discrimination at the time weren’t able to explain the wide and unique array of discrimination that Black women face. Basically, someone who identifies as both Black and a woman, faces different challenges due to discrimination than someone who identifies as Black and is not a woman or is a woman and who is not Black. Those challenges, like worse pay, housing, and job security, were not being acknowledged by theories that focused only on one part of a person’s identity.

Intersectionality helps us understand that we can’t untangle the different parts of our identities from one another. An intersectional approach to public health can help us better understand the context around health disparities and differences in health outcomes, and better tailor public health interventions to more fully meet the needs of people. For example, Black women diagnosed with HIV in the US can face an intersection of discrimination from racism, classism, sexism and HIV-related stigma.

The vulnerability that arises can impact their access and quality of health care, leading to an increased risk of poor health outcomes. So, an effective public health approach to HIV among Black women would need to account not for just the virus, but also the effects of this intersectional discrimination. People aren’t walking Ikea manuals, with each page having a detailed diagram of how one part of our identity fits neatly into the others.

The different parts of our identities–like our ethnicity, sexual orientation, and class –always interacting with our environments are never constant. The struggles that marginalized people experience from their identities isn't due to any identity itself, but rather society's unwillingness to accept certain identities and treat them fairly. People’s identities are kind of like the world’s most complicated pinball machines– if that pinball machine had a bazillion balls all ping-ponging off each other all the time.

So, if we’ve learned anything from these past two episodes, it’s that the ways society affects our health are complicated, and there’s no cookie-cutter solution that can improve health for everybody equally. Our bodies, environments, and society are all just too complicated and unpredictable. While we still have a long way to go, fortunately, recognition of all of this has led to new efforts by public health entities to fund and partner with community organizations to develop and tailor public health messages, prevention programs and solutions that are effective and relevant to people.

Our identities, society’s acceptance of those identities and the environment are all intertwined: we absolutely contain multitudes. And, when all this is properly taken into account, we can be nudged towards better health. Thanks for watching this episode of Crash Course Public Health, which was produced by Complexly in partnership with the American Public Health Association.

If you want to learn even more about Public Health, head over to APHA’s YouTube channel to watch “That’s Public Health” a series created by APHA and Complexly. Crash Course was filmed in the Castle Geraghty studio in Indianapolis, IN, and made with the help of all these kind people. If you'd like to help keep Crash Course free for everyone forever please consider joining our community of supporters on Patreon.