Two separate studies show a woman's risk for a first bout with depression rises sharply as she approaches menopause.
One of the studies measured hormone levels in 231 Philadelphia-area women over eight years and found that a woman's chances of tumbling into depression grew as her hormones changed.
The message for women at mid-life?
"It's not all in your head," said Ellen Freeman of the University of Pennsylvania School of Medicine and a co-author of the Philadelphia study.
Most women reach menopause without suffering depression, but both new studies suggest that some may be more sensitive to the transition.
"There is a subgroup of women who, for multiple reasons, may be more vulnerable," said Dr. Lee Cohen of Harvard Medical School, a co-author of the second study, which followed 460 Boston-area women for six years.
The Philadelphia study found that women with a history of premenstrual syndrome, or PMS, were more likely to experience depression when they neared menopause.
Cohen said women and their doctors shouldn't discount a disabling depression during the transition from normal menstrual cycles to the time when a woman's periods cease.
"Those who develop depression really need to be treated" with talk therapy, antidepressants or both, he said. Hormone therapy may be helpful to some women, he said.
The federally funded studies, published in the April issue of Archives of General Psychiatry, looked only at women with no prior history of depression. The women were in their 30s and 40s when the studies began.
Cohen and one of his co-authors noted in their paper that they have financial ties to several antidepressant manufacturers.
The Boston study found women nearing menopause were nearly twice as likely to develop symptoms of depression as women who hadn't yet experienced changes in their menstrual cycles. The Philadelphia study found that women who reported depressive symptoms were five times more likely to be nearing menopause.
Some medical experts have speculated that such depression may stem from sleep disruption caused by hot flashes. But both new studies found depression to be independent of that.
Still, in the Harvard study, the women most likely to get depressed were those who had both hot flashes and more stressful events in their lives, such as a family death or a divorce, noted Nancy Fugate Woods, nursing school dean at the University of Washington.
"It isn't possible, in the reality of women's lives, to tease those things apart completely," said Woods, who has done similar research, but was not involved with the new studies. "No matter how clever the research design is, you're still stuck with human beings", reports AP.