Women have long complained that their brains don't work as well during and after menopause as they did before. They complain of fuzzy thinking or difficulty finding the right words.
Recent research has offered conflicting evidence about the impact of menopause and hormone drugs on brain function.
Some research has suggested hormones may prevent Alzheimer's and dementia, but data from a major government study of menopause hormones showed just the opposite. That study, the Women's Health Initiative, found that older women who used menopause hormones were at higher risk for dementia than women in the study who didn't take hormones.
So what's the answer? There's growing evidence that hormones can both help and hurt the brain; it all depends on when women use them.
It appears that women who use hormones close to menopause - when their bodies are just experiencing a loss of estrogen - may show improvements in certain areas of cognitive function. But older women who take hormones long past menopause may be harmed by the drugs.
A recent Harvard study of 52 menopausal women ages 40 to 60 showed that hormones may help restore complex thinking skills muddled during the hormonal chaos of menopause.
Women receiving estrogen made 43 percent fewer errors in memory tests, according to a May report in the medical journal Menopause.
The Harvard study is in sharp contrast to the findings of the Women's Health Initiative, which suggested women who take hormones have a higher risk for dementia and other problems than nonhormone users.
But the WHI studies looked at women who started hormones between the ages of 65 to 79, past menopause, and many researchers believe the results don't apply to younger women.
Some researchers have speculated that the actual problem is that middle-aged women simply live more complicated lives - with constant multitasking, stress and too little sleep - than their 20- and 30-year-old counterparts.
Estrogen plays an essential role in brain function and appears to stimulate key brain chemicals linked to cognitive function. Brain-imaging studies show declines in brain activity when estrogen is in short supply.
But no one knows if brain scan changes mean anything.