Brain chemistry may hold clues to women's stress

A study has shown that females are more sensitive to low levels of a key stress hormone.

Although the research was conducted on rats, the same signalling pathway is known to play a role in human psychiatric conditions.

"This may help to explain why women are twice as vulnerable as men to stress-related disorders," said study leader Dr Rita Valentino, from The Children's Hospital of Philadelphia in the United States.

Women have higher rates of depression, post-traumatic stress disorder and other anxiety problems than men.

However no one has yet been able to pinpoint a biological reason for the difference.

The new research focuses on a hormone that organises stress responses in mammals called corticotropin-releasing factor (CRF).

A study of rats undergoing a swim stress test showed female animals had neurons that were more sensitive to CRF.

Stressed male rats adapted by making themselves less responsive to the hormone but females did not.

Dr Valentino said other mechanisms played a role in human stress responses but it was known that CRF regulation was disrupted in people with stress-related psychiatric disorders.

Much of the animal research on stress used only male rodents so important sex differences may have gone undetected.

The research is published online in the journal Molecular Psychiatry.