Slightly Off KIlter

Are you afraid of new situations? Or are you a bold adventurer?
Do you prefer predictable, familiar surroundings? Or do you like to explore and try new things?
You may feel safe, but you might not live as long as those who are less inhibited!
At least… if you’re a rat.

Some animals shy away from novel settings all their lives, preferring the predictability of familiar surroundings. Although this can be a safe strategy in the short run, it may have a fatal drawback down the line.

A new study finds that novelty-averse laboratory rats, after reaching maturity, died at markedly younger ages than did their more adventurous comrades. Heightened hormone responses to mildly stressful events throughout life ultimately undermined the capacity of the inhibited rats to resist tumors and other health threats, contend Sonia A. Cavigelli and Martha K. McClintock, both psychologists at the University of Chicago.

In essence, stress responses cause the inhibited rats to age prematurely, the researchers conclude in an upcomingProceedings of the National Academy of Sciences. These animals exhibit a 20 percent reduction in maximum life span compared with that of their bolder brethren.

“This is the first study to show that a psychological trait present from infancy can have life span consequences,” McClintock says. “I suspect this finding applies to people as well as to rats.”

[c.f. Worried to Death: Lifelong inhibitions hasten rodents’ deaths, Science News Online, Week of Dec. 13, 2003 ]

Apparently, the more cautious (“inhibited”) rats showed a higher stress reaction than their bolder friends. Scientists studied the blood levels of the stress hormone corticosterone in rats exposed to new situations and stressful settings. The “novelty-averse” rats displayed higher levels of the hormone, and the elevation lasted longer than in rats more eager to explore new situations.

An inhibited lifestyle comes with a health trade-off, McClintock theorizes. Cautious rats avoid predators and other dangers in their prime, but accumulated exposure to high levels of stress hormones renders them vulnerable to disease later in life.

“These are potentially important findings, but I’m cautious about accepting them,” remarks psychologist Jerome Kagan of Harvard University, who studies inhibited children. The results need to be confirmed in other strains of rats and with different measures of inhibition, he says.

Moreover, Kagan notes, risky behavior, rather than inhibition, causes people to die young.