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Fear of New Things May Shorten Life

Being afraid of new experiences may lead to a shorter life, new research in rats suggests.

Rats that were more fearful produced more stress-related hormones when exposed to new experiences and they tended to live shorter lives than less adventurous rats, researchers report.

"Young rats identified as fearful produce more stress hormones across the life span," Dr. Sonia Cavigelli of the University of Chicago's Institute for Mind and Biology told Reuters Health. The increased production of stress hormones may accelerate aging, she said.

Whether the same is true in people is uncertain, but studies have shown that shy children experience a surge in stress hormones when confronted with something new.

"We should consider how personality and other behavioral traits affect our physiology and what kind of impacts these traits could have on our health over the life span," Cavigelli said.

In rats that were more fearful than others, the trait showed up early in life and persisted throughout life, Cavigelli and Dr. M. K. McClintock report in the early online edition of the journal Proceedings of the National Academy of Sciences.

When placed in a new environment, fearful rats were hesitant and did not explore their new surroundings very much. In contrast, rats that were not fearful moved throughout their new surroundings and inspected objects around them.

Fearfulness was apparent in rats early in life, even before they were weaned, and it persisted into adulthood, according to the report. Compared to other rats, fearful rats experienced a surge in hormones called glucocorticoids after being exposed to something new.

What's more, fearful rats lived an average of 20 percent shorter lives than more adventurous rats.

The association between increased secretion of stress hormones and a shorter life suggests that the hormones may gradually cause damage that accelerates aging, according to the researchers.

But it is important to note, according to Cavigelli, that fearfulness or shyness may not always be a negative trait.

"I believe that this fearful trait may actually be quite beneficial, for example," Cavigelli said. "It may be the one thing that keeps individuals from engaging in needless risky behavior."

Future research should focus on how social experiences early in life affect the development of fearfulness, according to the Chicago researcher. For example, one question that needs to be answered is how early social interactions affect the development of fearfulness, she said.

In addition, future studies in rats may identify other health-related differences between fearful and adventurous rats, Cavigelli said.

SOURCE: Proceedings of the National Academy of Sciences 2003.

Reference Source 89


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