To confront a modern phenomenon, the country's growing depression epidemic, psychologist Steve Ilardi peered back into human history.

Way back: tens of thousands of years and beyond. His research steered him there, to an examination of the hunter-gatherer way of life, to a time when humans lived in roving, close-knit bands. Back to the Stone Age.

What he learned led Ilardi and his research team at the University of Kansas to propose a program to reclaim six disappearing lifestyle elements. They call it Therapeutic Lifestyle Change, intended to help modern humans deal with depressive illness.

The team identified factors that are antidepressant but are compromised by contemporary culture: Exercise, omega-3 consumption, light exposure, sleep, social connectedness and anti-ruminative behavior.

The latest and sobering statistics predict that one in four Americans will become clinically depressed by age 75, Ilardi said. Americans are 10 times more likely to have depressive illness than they were 60 years ago.

Ilardi is an associate professor of psychology, not a self-help guru. And he knows the hunter-gatherer talk can sound a little wacky. But he said his early results are showing phenomenal success.

About a year ago Becky Foerschler of Lawrence, Kan., a mother of three, felt herself drifting, pulling back from social commitments, uncharacteristically sapped of energy.

Foerschler's situation wasn't dire. But a series of stressful family matters had preceded her troubling lethargy, and friends hinted that her symptoms looked like depression.

"I thought, 'This isn't something that's going to go away by itself.'"

She wasn't keen on taking antidepressant drugs, so when she heard about Ilardi's research, she called to make an appointment. She met with therapists and was accepted into the program.

Depression treatment often centers on talk therapy and antidepressant drugs. The drugs have been lifesavers for many people.

But antidepressants aren't working as well as advertised, Ilardi said, and their side effects can go from bad to devastating, including suicide.

Depressive illness is more frequent in developed countries than in developing ones and worse among city dwellers than among rural folks. The Amish have very low depression rates.

An anthropologist who studied the Kaluli people, a modern-day hunter-gatherer group in Papua New Guinea, found only one case of depression. Like hunter-gatherers of old, the Kaluli lack modern comforts and medicine. They deal regularly with infant mortality, disease and violence.

Culturally the contrast with modern Americans is huge. Biologically, however, we're not so different, not even from the hunter-gatherer clans going back hundreds of thousands of years.

"In many respects we're walking around with Stone Age brains and Stone Age bodies," Ilardi said.

Rapid cultural change is relatively recent, starting with farming, then city-building, then the technological explosion. So Ilardi asked: Are there built-in features of that ancient way of life that are antidepressant and that we need to reclaim?

Hunter-gatherers walked for miles. They got lots of light exposure. They slept when the sun was down. And they ate differently.

So far the program has treated 31 clinically depressed adults. Ilardi is impressed with the results: 86 percent recovered fully or had a significant reduction in symptoms.

Rick Ingram, KU professor of psychology, was skeptical of Ilardi's program at first but sees the results as promising. One caveat is that the treatment program requires further testing, done independently from Ilardi's team.

"This is an innovative program in its initial stages, and, as such, the data are not fully in," he said.

Ingram said the Therapeutic Lifestyle Change program, rather than competing with traditional therapies, could eventually be used in conjunction with them.

"Areas of biology and psychology converge in this program," Ingram said. "The innovation is in bringing them all together."

In the 12-week program the 90-minute, weekly sessions are led by two clinicians and include five to eight clients. The six elements are introduced one week at a time. Clients talk with therapists by phone between sessions.

Foerschler completed the program last summer and remains free of symptoms.

"By the sixth week I was definitely noticing a difference, and by the end of the 12 sessions I wasn't having any symptoms," she said.