Elizabeth Blackburn has always been fascinated by how life works. Born in 1948, she grew up by the sea in a remote town in Tasmania, Australia, collecting ants from her garden and jellyfish from the beach. When she began her scientific career, she moved on to dissecting living systems molecule by molecule.

Working with biologist Joe Gall at Yale in the 1970s, Blackburn sequenced the chromosome tips of a single-celled freshwater creature called Tetrahymena (“pond scum”, as she describes it) and discovered a repeating DNA motif that acts as a protective cap. The caps, dubbed telomeres, were subsequently found on human chromosomes too. They shield the ends of our chromosomes each time our cells divide and the DNA is copied, but they wear down with each division. In the 1980s, working with graduate student Carol Greider at the University of California, Berkeley, Blackburn discovered an enzyme called telomerase that can protect and rebuild telomeres. Even so, our telomeres dwindle over time. And when they get too short, our cells start to malfunction and lose their ability to divide – a phenomenon that is now recognised as a key process in ageing. This work ultimately won Blackburn the Nobel Prize in Physiology or Medicine.

In 2000, she received a visit that changed the course of her research. The caller was Elissa Epel, a postdoc from UCSF’s psychiatry department. Psychiatrists and biochemists don’t usually have much to talk about, but Epel was interested in the damage done to the body by chronic stress, and she had a radical proposal.

Epel, now director of the Aging, Metabolism and Emotion Center at UCSF, has a long-standing interest in how the mind and body relate. Her work, she says, is influenced by the holistic health guru Deepak Chopra, and the pioneering biologist Hans Selye, who first described in the 1930s how stressed rats can become chronically ill. “Every stress leaves an indelible scar, and the organism pays for its survival after a stressful situation by becoming a little older,” Selye said.

Back in 2000, Epel wanted to find that scar. “I was interested in the idea that if we look deep within cells we might be able to measure the wear and tear of stress and daily life,” she says. After reading about Blackburn’s work on ageing, she wondered if telomeres might fit the bill.

‘Another world’

With some trepidation, she asked Blackburn for help with a study of mothers going through one of the most stressful situations that she could think of – caring for a chronically ill child. Epel’s plan was to ask the women how stressed they felt, then look for a relationship between their state of mind and the state of their telomeres. Collaborators at the University of Utah would measure telomere length, while Blackburn’s team would measure levels of telomerase.

Blackburn’s research until this point had involved elegant, precisely controlled experiments in the lab. Epel’s work, on the other hand, was on real, complicated people living real, complicated lives. “It was another world as far as I was concerned,” says Blackburn. At first, she was doubtful that it would be possible to see any meaningful connection between stress and telomeres. Genes were seen as by far the most important factor determining telomere length, and the idea that it would be possible to measure environmental influences, let alone psychological ones, was highly controversial. But as a mother herself, Blackburn was drawn to the idea of studying the plight of these stressed women. “You can’t help but empathise.”

It took four years before they were finally ready to collect blood samples from 58 women; this was a small pilot study. To give the highest chance of a meaningful result, the women in the two groups – stressed mothers and controls – had to match as closely as possible, with similar ages, lifestyles and backgrounds. Epel recruited her subjects with meticulous care. Still, Blackburn says, she saw the trial as nothing more than a feasibility exercise. Right up until Epel called her and said, “You won’t believe it.”