For the first time, research shows that stress speeds the aging process by harming DNA. But CBS News Correspondent Scott Pelley says there's a silver lining in that seemingly dark cloud: We have a say in the stress-aging relationship. We can offset the impact of stress.

Did you ever know someone under so much stress they aged right before your eyes?

It seems to happen to presidents after a term or two, and maybe you've noticed something similar in your own mirror.

Now, for the first time, a medical study has proven what we've all suspected: Stress speeds up aging.

And CBS News Correspondent Scott Pelley reports it does this by reaching all the way down into your cells and damaging your DNA. In a sense, chaos is crunching your chromosomes.

But don't stress out yet. Pelley points out that there is a way to prevent the damage.

It was discovered last November in a project that followed women with real-life stress. It then peered inside to see their cells aging before their time.

When the researchers were looking for women to study, Eileen Attridge appeared to be the perfect subject.

The study needed 30 volunteers suffering the same kind of constant aggravation. So, naturally, they picked mothers but, more than that, mothers like Eileen, who all care for chronically ill children. Her daughter, 12-year-old Rosie, is autistic.

Dr. Elissa Epel headed the stress study, at the University of California, San Francisco.

"I chose the mothers," Epel told Pelley, "because they tend to be a group that's under chronic stress at a very young age. But they're young and healthy, so it gives us an opportunity to examine what chronic stress looks like in healthy people."

The first thing Epel had to do was measure how each mom coped with stress. Were they the kind who held up or the kind who fell apart? Epel designed a test that pushes their anxiety buttons. It measured their heart rates, blood pressure and perspiration rates.

Epel explained its premise, namely that, "The unpredictability and ambiguity, not knowing what you're gonna have to do, is stressful."

Such as solving a difficult math problem in front of a stern professor.

The test showed how stress affected the moms physically. But Epel also needed to know how it tortured them mentally. How well did each mom cope while caring for a sick child?

To see how they felt about anxiety, Epel had each mother answer a series of questions.

She says a psychologist took "everything we know about stress, and what's stressful, and put it into one questionnaire."

Pelley tried his hand at the questionnaire, as he put it, against his better judgment.

Epel asked how he felt about stress during the past month, rating it from zero, the least, to four, which was over the top.

"I am saddened to tell you," Epel observed, "that you actually scored in our caregiver range."

Meaning: high stress.

Dr. Elizabeth Blackburn, a world-renowned cellular biologist at the University of California, San Francisco, was Epel's partner in the study.

"To find something that goes to the heart of how cells age and find it so consistently related to stress, chronic stress and bad stress, that's the thing that's so new and intriguing here," she says.

Blackburn's job was to look at the cells of the moms in the study to see if they were getting old too soon.

To find out, she looked at the part of the DNA that controls cell aging. It's called a telomere. Blackburn discovered telomeres 20 years ago, and told Pelley how they work: If you think of a strand of DNA as a shoelace, the telomere is the plastic tip on the end. It protects the DNA from damage. Telomeres naturally get thinner as we age, and the thinner they get, the thinner the protection.

"It turns out you have to have enough of the telomeres at the end," Blackburn says. "And if it gets disrupted in some way, it gets frayed away."

When it frays away, the cell dies. That's why, Pelley notes, we lose eyesight, hearing and muscle strength as we get older.

To see what it's like when telomere thin before their time, Pelley paid a visit to Gene Trester. He has a rare genetic disease, unrelated to stress, that has shortened his telomeres years too soon.

"We were at the miniature golf course the other week with the girls," Trester said. "And they gave Grandpa the senior discount."

He isn't their grandfather. Trester is their 52-year-old father. He's living proof that it's not the length of years, but the length of telomeres that matters most in aging.

"On bad days," he says, "I actually have to take a nap like an old person, you know."

While Trester's telomeres are short because of his disease, Blackburn and Epel have shown, for the first time, that stress has a similar effect, thinning the telomeres of the stressed-out moms.

"We were astounded," Blackburn says, "that they were absolutely, consistently showing that the shorter the telomeres were, the worse stress people had had. That said, that these cells aged much faster than they should have been aging if they had not had that stress.

"It was as though there had been in excess of 10 years of extra aging in these individuals' blood cells. And that's actually an underestimate. That's a very conservative estimate."

But there was something else they found, too.

Remember that stress test? It turns out the mothers who cope well under stress, who don't let it get under their skin, don't suffer the same damage to their telomeres.

It may be hard to image a more stressful life than the one Eileen Attridge shares with her autistic daughter, Pelley says. Still, Eileen's telomeres are just fine, which came as no surprise to her.

"I have a great attitude," she says, "because that's what I give myself to do. That's my goal, to have a good attitude. Because if I didn't have a good attitude, who'd want to talk to me?"

"That's what's so interesting in psychology," Epel points out, "is to try to understand resilience. How is it that some people are resilient in the face of chronic stress?"

It appears, Pelley says, that resilience can ward off sickness and let us live longer, while those who feel overwhelmed by life may have a shorter one to live.

"I think that this is yet another call to people to be alarmed about their stress levels," Epel says, "and to take them seriously. The cell is not a closed system. ...What happens in the mind, in particular, perceptions of stress, can indeed affect the most fundamental unit of our physical beings."