Narrator: This is Science Today. It's been known for decades that poverty is linked to higher rates of illness and death. But a University of California, San Francisco study has found a link between health and socioeconomic status that goes beyond the poverty line. Psychiatrist Nancy Adler, who led the study, says people who considered themselves higher up on the social ladder tended to be healthier and less stressed.

Adler: In some ways it's equivalent to the animal research. If you study non-human primates, you can see very clearly that they've formed dominance hierarchies and the more dominant animals are healthier and being lower in the social hierarchy there has the same kinds of associations as with humans. They have more athlerosclerosis, they have higher levels of cortisol, which is a stress hormone, and they live shorter lives.

Narrator: Adler says their study is consistent with the idea that stress determines health.

Adler: It suggests one way this may operate is that people who feel themselves chronically lower on the hierarchy may feel a sense of chronic stress and then that has to do with possible interventions to buffer some of the biological effects of stress.

Narrator: For Science Today, I'm Larissa Branin.