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In July 2019, Milwaukee became the first city to declare racism a public health crisis. And almost one year later, dozens of other cities have begun to follow suit, in response to the protests ignited after Minneapolis police killed George Floyd.

If it seems surprising that we’re talking about this on SciShow, well, there is science here. In addition to being a serious social issue, racism is also a serious challenge to public health. It affects the well-being of people who are subject to racism in every way, including physically—and this is what we’re going to talk about in particular here.

In the U. S., there are significant health disparities between groups of different races—with some of the largest gaps between white and Black people. And it’s maybe worth emphasizing that these racial health disparities are not rooted in biology.

All humans are over 99.9% genetically identical. And even those differences in that are in the 0.01% are not determined by race. So while people of different ancestry are occasionally predisposed to one disease or another, study after study has refuted the notion that this could account in any way for the health disparities we see today.

And that has a lot to do with systemic racism: the type of racism that’s built into the fabric of society, through laws and structures that promote and sustain racial inequality. And it’s important to note that systems of oppression can build upon each other to the point that they can become hard to recognize—especially for the communities that benefit from them. And that’s often the case, even though, in countries like the U.

S., they’ve been in place since the founding of the country. But whether or not we recognize it, systemic racism leads to racial disparities in practically everything that impacts well-being, like access to nutritious food, healthcare, and quality schools. It also leads to pervasive discrimination from law enforcement officers, clinicians, employers, and others, many of whom have been trained and educated in racist systems.

And all of these things have an enormous impact on people’s health throughout their whole lives, even when it is not obvious. But systemic racism is often compounded by individual discriminatory incidents—like, when a person gets harassed, or treated poorly at a restaurant, or unfairly dismissed from a job. In situations like these, where a person is aware that they are being mistreated because of their race, that can also have a significant health toll.

And that’s mostly what we’ll focus on here. In 2019, a study in the journal Health Services Research looked at 29 literature reviews and meta-analyses on self-reports of discrimination. And it found that perceived racial discrimination is linked to mental and physical health in all kinds of ways.

People who experience it have higher rates of sleep problems, cardiovascular disease, and premature births, as well as higher levels of stress hormones like cortisol. And systemic racism is part of that. Things like unequal access to resources and constant discriminatory treatment by institutions account for a lot of health disparities.

But scientists don’t think that’s the whole story. That's because having discriminatory experiences is stressful. And stress can wreak all kinds of havoc on the body.

Again, it’s definitely hard to tease that apart from the stress of systemic racism, but some studies have tried to address that by getting really specific. Like, in a 13-year study published in 2020, scientists looked specifically at how hypertension, or high blood pressure, related to rates of discrimination. The survey began in 2000 with a group of nearly 2000 participants living in Jackson, Mississippi, who did not have hypertension at the time.

At the beginning of the study, researchers conducted a standardized survey about racial and other forms of discrimination they’d experienced over the course of their lives. This included experiences they’d had in public places, at school or work, or in receiving services, housing, or other resources. Those who reported medium or high lifetime discrimination were up to 49% more likely to eventually develop hypertension.

And it’s not just Mississippi here. Other studies conducted in various geographic areas also suggest an association between lifetime racial discrimination and hypertension among specific ethnic and racial groups. These are just associations, so they can’t prove that perceived incidents of discrimination cause hypertension.

But there are plausible explanations for why that would happen. For example, experiments in which Black subjects were exposed to racist content or situations have shown an immediate rise in blood pressure. Researchers think that the stress response of these situations triggers the body’s fight-or-flight response.

So the brain releases a surge of stress hormones, which cause the blood vessels to constrict and the heart rate to jump, creating a spike in blood pressure. Combined with the forces of systemic racism, which come largely from institutions and policies, these experiences add up over time. And they’ve been linked with things like chronic hypertension and other health conditions.

Researchers haven’t figured out exactly how these chronic conditions develop, but some evidence suggests that the stress of racism repeatedly triggers the body’s stress response system, known as the hypothalamic-pituitary-adrenal axis. And while we don’t know exactly how, some researchers think that this repeated triggering can have long-term consequences. In addition to effects like these, racism may also bring about long-lasting changes in people’s blood cells themselves.

That’s because the release of stress hormones can change the expression of genes in your cells. Gene expression happens when an enzyme reads the genetic information in a gene and uses that information to build a protein. And that protein produces a certain trait.

But depending on a bunch of different factors, genes can either be expressed, where they build those proteins, or suppressed, when they don’t. In this case, stress hormones can cause cells to express genes involved in inflammation. They can also make the cells suppress genes that help fight off viruses —in order to divert energy to immediate threats.

Unfortunately, while inflammation can be helpful for the body to heal from injury and fight off infections, when it’s ongoing, it can do more harm than good. Like, inflammation can cause swelling of airways, which makes people more susceptible to asthma attacks. It can also cause plaque lining the walls of blood vessels to break off and form blood clots, which can cause heart attacks and strokes.

Now racism of course isn’t the only kind of stress that can cause these reactions in the body, but in 2019, the authors of a small study in the journal Psychoneuroendocrinology looked specifically at the link between these effects and racism. They found that racial discrimination was associated with higher levels of inflammation in Black versus white participants. And separate studies have found that inflammation caused by racism seems to play a role in many racial health disparities.

The exact mechanisms aren’t always clear, but it has been linked with disparities in overall cardiovascular health, preterm birth rate, and even chronic pain. You may sense a pattern here: The impacts of racial discrimination aren’t just short-term. The experience of racism in childhood or adolescence can affect people in many different ways for the rest of their lives.

Some evidence even suggests that those effects can be passed down. While someone is pregnant, their stress can take a toll on the developing fetus. Stress hormones can even pass through the placenta to the fetus.

The result is potentially a vicious cycle: Health conditions in the womb compound lifelong effects of racism, and can affect people’s health for generations. But researchers have emphasized that while this type of intergenerational trauma is one factor, external factors —like cycles of poverty caused by systemic racism—take an even bigger toll. So from discriminatory treatment in systems to the effects of stress on cells—on every level, racism causes and perpetuates the massive health disparities in this country.

And this is why, after centuries of racism, cities and counties all over the U. S. are now declaring it a public health crisis. It’s a small step, and governments aren’t the only ones responsible for perpetuating or solving racism—but it is a step.

Thank you for watching this episode of SciShow Psych! And thank you to our patrons, who make videos like this possible. It takes a lot of people to make a SciShow video and we couldn’t do it without your support.

If you’d like to find out more about how to support us, check patreon.com/SciShow. [♪ OUTRO].