Jul 22, 2010

Study points to why stress may affect women more



There may be a bi­o­log­i­cal rea­son why more wom­en than men suf­fer stress-related psy­chi­at­ric dis­or­ders, a study sug­gests.

Stud­y­ing stress sig­nal­ing mo­le­cules in rat brains, re­search­ers found that fe­males are more sen­si­tive than males to low lev­els of a ma­jor stress hor­mone, and less able to adapt to high lev­els of it.

Stud­y­ing stress sig­nal­ing mo­le­cules in rat brains, re­search­ers found that fe­males are more sen­si­tive than males to low lev­els of a ma­jor stress hor­mone, and less able to adapt to high lev­els.

“This is the first ev­i­dence for sex dif­fer­ences” in this sig­nal­ing sys­tem, said study lead­er Rita J. Val­en­ti­no, a be­hav­ior­al neu­ro­sci­ent­ist at The Chil­dren’s Hos­pi­tal of Phil­a­del­phia. Her re­search ap­peared on­line June 15 in the re­search jour­nal Mo­lec­u­lar Psy­chi­a­try.

The gen­der dif­fer­ences, she ex­plained, in­volve the way mo­lec­u­lar struc­tures on brain cell sur­faces, called re­cep­tors, han­dle the traf­fic of stress sig­nal­ing molecules. “Although more re­search is cer­tainly nec­es­sary to de­ter­mine wheth­er this trans­lates to hu­mans, this may help to ex­plain why wom­en are twice as vulnera­ble as men to stress-related dis­or­ders,” she added.

Wom­en have a high­er in­ci­dence of de­pres­sion, post-traumatic stress dis­or­der, and oth­er anx­i­e­ty dis­or­ders, said Val­en­ti­no.

Her re­search fo­cus­es on corticotropin-releasing fac­tor, or CRF, a hor­mone that or­ga­nizes stress re­sponses in mam­mals. An­a­lyz­ing the brains of rats put through a swim stress test, Val­en­ti­no’s team found that in fe­male rats, brain cells had re­cep­tors for CRF that at­tached more tightly to cell sig­nal­ing pro­teins than in male rats. The re­cep­tors thus re­sponded more strongly to the stress hor­mone.

Fur­ther­more, Val­en­ti­no said, stressed male rats dis­played an adaptive re­sponse, called in­ter­nal­iz­a­tion, in their brain cells. These cells re­duced the num­ber of CRF re­cep­tors, and be­came less re­spon­sive to the hor­mone. In fe­male rats this did­n’t hap­pen be­cause a spe­cif­ic pro­tein did not link up with the CRF re­cep­tor in a way that was needed for this adapta­t­ion, Val­en­ti­no ex­plained.

“We can­not say that the bi­o­log­i­cal mech­an­ism is the same in peo­ple,” she added, not­ing that oth­er mech­an­isms and hor­mones play roles in hu­man stress. But “re­search­ers al­ready know that CRF regula­t­ion is dis­rupted in stress-related psy­chi­at­ric dis­or­ders, so this re­search may be rel­e­vant to the un­der­ly­ing hu­man bi­ol­o­gy.”

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