The modern idea of stress began on a rooftop in Canada, with a handful of rats freezing in the winter wind.
This was 1936 and by that point the owner of the rats, an endocrinologist named Hans Selye, had become expert at making rats suffer for science.
"He would subject them to extreme temperatures, make them go hungry for long periods, or make them exercise a lot," the medical historian Mark Jackson says. "Then what he would do is kill the rats and look at their organs."
We women are all too aware that as we get older the risk of having a baby with genetic disorders goes up. All of a woman's eggs are primed up and ready to go before we are born. But the ones we ovulate later are more prone to genetic errors than the earlier ones.
As a friend of mine surmised, "We age, so you kind of think our eggs would, too."
For a long time, doctors have thought that was because the eggs formed earlier are better than those formed later. They call it the "production-line hypothesis."
Everyone seems to talk about feeling stressed out. But what's the reality of stress in America these days?
NPR, the Robert Wood Johnson Foundation and the Harvard School of Public Health conducted a nationwide poll in March and early April to find out.
Our questions zeroed in on the effect of stress in Americans' lives. We asked about people's personal experiences with stress in the preceding month and year. We also asked about how they perceived the effects of stress, how they cope with stress and their attitudes about it.
A good night's sleep is rare for Judy and James Lee. They are on parenting duty 24/7 for their son, Justin.
Justin, who has cerebral palsy and was born missing parts of his brain, also has a seizure disorder, which has gotten worse lately. He's often silent during his seizures, which means he has to sleep with his parents so they can tell when he needs help. Judy says caring for Justin is a lot like taking care of a newborn.