Even on a molecular level, the human body is able to distinguish between a sense of well-being derived from a profound, "noble" purpose versus simple self-gratification, a new study published in the Proceedings of the National Academy of Sciences reports.

Led by Barbara L. Fredrickson, Kenan Distinguished Professor of psychology in the College of Arts and Sciences at the University of North Carolina at Chapel Hill, the researchers looked at looked at the biological influence of the two forms of happiness through the human genome.

"Philosophers have long distinguished two basic forms of well-being: a 'hedonic' form representing an individual's pleasurable experiences, and a deeper 'eudaimonic,' form that results from striving toward meaning and a noble purpose beyond simple self-gratification," wrote Fredrickson and her colleagues.

It's the difference, they explained, between enjoying a good meal and feeling connected to a larger community through a service project.

While both offer a sense of satisfaction, each is experienced very differently in the body's cells.

"We know from many studies that both forms of well-being are associated with improved physical and mental health, beyond the effects of reduced stress and depression," Fredrickson said. "But we have had less information on the biological bases for these relationships."

Collaborating with a team from the University of California at Los Angeles led by Steven W. Cole, professor of medicine, psychiatry and behavioral sciences, Fredrickson and her colleagues focused on the pattern of gene expression within people's immune cells.

Past work by Cole and colleagues showed a systematic shift in gene expression associated with chronic stress that, the study noted, was "characterized by increased expression of genes involved in inflammation" implicated in a wide variety of human ills, including arthritis and heart disease, and "decreased expression of genes involved in ... antiviral responses."

In order to describe this shift, Cole and his fellow researchers coined the phrase "conserved transcriptional response to adversity," or CTRA.

However, if all happiness is created equal, and if all forms of well-being are equally opposite to "ill-being," then the patterns of gene expression would be identical regardless of the source of the sense of well-being, the scientists hypothesized.

This, it turned out, was not the case.

While eudaimonic well-being was associated with a significant decrease in the stress-related CTRA gene expression profile, hedonic well-being was associated with a significant increase in the CTRA profile.

Fredrickson said she found the results initially surprising since study participants themselves reported overall feelings of well-being.

One possibility for the discrepancy, she suggested, is that people who experience more hedonic than eudaimonic well-being consume the emotional equivalent of empty calories.

"We can make ourselves happy through simple pleasures, but those 'empty calories' don't help us broaden our awareness or build our capacity in ways that benefit us physically," she said. "At the cellular level, our bodies appear to respond better to a different kind of well-being, one based on a sense of connectedness and purpose."