January 14, 2016

Hormones are Emma Adam's thing. And one in particular: cortisol, which regulates how tired (or awake) you are.

Cortisol acts as a counterweight to insulin, and it responds very noticeably to stress.

Adam, a faculty fellow at the Institute for Policy Research at Northwestern, tracks cortisol levels by collecting people’s spit at different points during the day. And she says there’s a clear pattern: high levels in the morning and low levels in the evening.

But about a decade ago, Adam noticed something curious.

Different teenagers have different levels of cortisol. Some have that spike you would expect in the morning, which then drops throughout the afternoon and into the evening.

But some have a much flatter, more constant level during the day. These teenagers might not get that hit of energy in the morning, and it might be tougher for them to go to sleep at night.

When Adam looked, she found that the teenagers who happened to have these flatter levels were more often African-American than white. And she started to wonder why there was a gap.

One possibility was that discrimination was playing a role. So she asked teenagers whether they felt discriminated against on various days, and then checked their cortisol levels on those days. True to her suspicion, she found a relationship between a flattened cortisol level and discrimination.

But it didn’t fully explain those racial differences. Adam thought that maybe it wasn’t just discrimination in the present, but a lifetime of discrimination that could cause differences between the teens.

The tricky part was going to be testing this theory. Unless she wanted her study to take decades.

And then she got lucky.

Adam realized that about a quarter century ago, in 1991, researchers at the University of Colorado and the University of Michigan wanted to figure out why some kids go on to succeed in life - and others don't.

They decided the only way to really do the study right was to follow kids for a long time.

About 60% of the families they tracked were African American, and the researchers checked in with these kids for years, asking them all sorts of questions, like: At school, do you feel like teachers call on you less because of your race?

For 20 years, researchers kept coming back and checking in with the participants. Adam knew that if she and her colleagues could look back and see whether the kids in the study had felt discriminated against, then she could test their cortisol levels as adults and have the data she needed.

It turned out that lifetime discrimination was indeed strongly linked to whether your cortisol curve looked normal or unusually flat.

But there was a twist. It mattered when in life you were discriminated against. Being discriminated against as a teenager had a greater effect than being discriminated against as an adult.

Now, Emma Adam says what she’s looking for is a kind of magic shield that can help adolescents ride out tough times, so they don't permanently impact health. “One thing we’re looking at is racial ethnic identity,” says Adam. “Does discrimination have less of an effect on a strong ethnic identity? Are those kids protected?”

emma adam, institute for policy research, Northwestern, Sci and Tech

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