( A new brain study finds major differenc...)New brain-chemistry differences found in depressed women

The study adds further evidence that depression has its roots in specific alterations within the brain -- specifically in the endogenous opioid system that is a central part of the brain's natural pain and stress-reduction system. The findings also show significant variation between individuals with depression ?variation that seems to be linked to whether or not the patients respond to an antidepressant medication.

The study, performed by researchers at the University of Michigan Medical School affiliated with the U-M Depression Center, is published in the November issue of the Archives of General Psychiatry. It's based on brain imaging, blood chemistry and other data from 14 women with major depression, and 14 healthy women of about the same age and background. The women with depression were not taking antidepressants when the study began.

"This work gives further evidence of individual differences in brain mechanisms that are altered in major depression," says senior author Jon-Kar Zubieta, M.D., Ph.D., the Jenkins Research Professor of Depression and associate professor of psychiatry and radiology. "We found these differences in the response of the endogenous opioid system. Some women, but not others, with major depression, showed exaggerated responses in this system when undergoing an emotional challenge."

That emotional challenge was the summoning of memories of a very sad event in their lives, which the researchers asked the women to recall while they were lying in the positron emission tomography (PET) scanner having their brains imaged. The women recalled the death or serious illness of a friend or family member, a past divorce or breakup with a boyfriend, or other major difficulties. They also had their brains imaged during a neutral emotional state.