Why Some People Cope with Stress and Some Cave: Genes Hold the Key

Some people cave under stress while others take it in stride. Now, scientists have found out why stress may just be more devastating to some. They've identified the molecular mechanisms of a so-called stress gap in mice that may shed light on anxiety and depression.

"Like people, each animal has unique experiences as it goes through its life," said Bruce McEwen, senior author of the new study, in a news release. "And we suspect that these life experiences can alter the expression of genes, and as a result, affect an animal's susceptibility to stress. We have taken an important step toward explaining the molecular origins of the stress gap by showing that inbred mice react differently to stress, with some developing behaviors that resemble anxiety and depression, and others remaining resilient."

In order to examine the effects of stress, the researchers turned to mice. They exposed the animals daily to unpredictable bouts of cage tilting, altered dark-light cycles, confinement in tight space, and other conditions that mice dislike. After, the scientists found that about 40 percent of the mice showed high levels of behaviors that indicated stress. The remaining 60 percent coped well with the stress.

So why did some mice act one way and others act the other way? They found that the stress-susceptible mice had less of an important molecule known as mGlu2 in a stress-involved region of the brain known as the hippocampus. A decrease of the molecule resulted from an epigenetic change, which affects the expression of genes.

Currently, depression is diagnosed only by its symptoms," said Carla Nasca, first author of the new study. "But these results put us on track to discover molecular signatures in humans that may have the potential to serve as markers for certain types of depression. Our work could also lead to a new generation of rapidly acting antidepressants, such as acetyl carnitine, which would be particularly important to reduce the risk of suicide."

The findings are published in the journal Molecular Psychiatry.