A new study has found that premenstrual dysphoric disorder (PMDD) is biologically different from major depression and a history of depression affects how women with PMDD respond to stress and pain.
PMDD is often misdiagnosed as major depression or other mood disorder.
However, the new findings are important because they give physicians more reason to search for a more specific diagnosis and could possibly lead to more precise treatments, of which there are currently few good choices, said Dr. Susan Girdler, professor of psychiatry at the University of North Carolina at Chapel Hill School of Medicine who led the study.
"PMDD is not garden-variety premenstrual symptoms. PMDD causes severe impairment in quality of life, equivalent to post-traumatic stress disorder, major depressive disorder and panic disorder, which continually cycles on a monthly basis. Some women spend half their lives suffering from this disorder," said Girdler.
In the study, the researchers measured biological responses to stress and pain.
Previous studies demonstrated that women with chronic major depression have a heightened biological response to stress and release more stress hormones, such as cortisol.
And, Girdler and her group have previously shown that women with PMDD respond conversely, with blunted stress responses.
The current study is the first known head-to-head comparison of the two groups and confirmed earlier findings.
"We found the greatest weight of evidence that PMDD and major depression are really two distinct entities in terms of iological response to stress and with respect to pain sensitivity and pain mechanisms," said Girdler.
But, he said that more important was the finding that women with PMDD who also had experienced depression in the past looked different from PMDD women who had never been depressed.
Only the PMDD women with prior depression had lower cortisol and greater sensitivity to pain compared to non-PMDD women with prior depression.
These differences between PMDD and non-PMDD women were not seen in women who had no depression history.
"So while the study shows that PMDD is biologically different from major depression, a history of depression may have special relevance for women with PMDD with respect to stress hormones and pain response," said Girdler.
Current treatments for PMDD are effective in only about half of women.
But, Girdler said that gathering more biological clues about PMDD could expand the treatment options.
The study has been published in the journal Biological Psychology.