context: It's clear that estrogen is closely linked with women's emotional well-being. Depression and anxiety affect women in their estrogen-producing years more often than men or postmenopausal women. Estrogen is also linked to mood disruptions that occur only in women -- premenstrual syndrome, premenstrual dysphoric disorder, and postpartum depression. Exactly how estrogen affects emotion is much less straightforward. Is it too much estrogen? Not enough? It turns out estrogen's emotional effects are nearly as mysterious as moods themselves. Beginning at puberty, a woman's ovaries start releasing estrogen in coordination with each monthly menstrual cycle. At mid-cycle, levels suddenly spike, triggering the release of an egg (ovulation). They then fall just as quickly. During the rest of the month, estrogen levels climb and fall gradually. Normal estrogen levels vary widely. Large differences are typical in a woman on different days, or between two women on the same day of their cycles. The actual measured level of estrogen doesn't predict emotional disturbances. That's not to say estrogen isn't a major player in regulating moods. Estrogen acts everywhere in the body, including the parts of the brain that control emotion. Some of estrogen's effects include: Increasing serotonin, and the number of serotonin receptors in the brain. Modifying the production and the effects of endorphins, the "feel-good" chemicals in the brain. Protecting nerves from damage, and possibly stimulating nerve growth. What these effects mean in an individual woman is impossible to predict. Estrogen's actions are too complex for researchers to understand fully. As an example, despite estrogen's apparently positive effects on the brain, many women's moods improve after menopause, when estrogen levels are very low. Some experts believe that some women are more vulnerable to the menstrual cycle's normal changes in estrogen. They suggest it's the roller coaster of hormones during the reproductive years that create mood disturbances. As many as 90% of women experience unpleasant symptoms before their periods. If symptoms are reliably severe enough to interfere with quality of life, it's defined as premenstrual syndrome ( PMS). Generally speaking, PMS is present when: Physical and emotional symptoms occur reliably a few days before multiple consecutive menses (periods). The symptoms go away after completing a period and don't occur at other times. The symptoms cause significant personal problems (such as at work, school, or in relationships). No medicines, drugs, alcohol, or other health condition might be to blame. Bloating, swelling of arms or legs, and breast tenderness are the usual physical symptoms. Feeling overly emotional, experiencing depression, anger and irritability, or having anxiety and social withdrawal may be present. As many as 20% to 40% of women may have PMS at some point in life. As with PMS, women with premenstrual dysphoric disorder ( PMDD) regularly develop negative mood symptoms before their periods. Some experts consider premenstrual dysphoric disorder to be a severe form of PMS. In PMDD, mood symptoms are more severe and often overshadow physical symptoms. The emotional disturbances are significant enough to cause problems with daily life. From 3% to 9% of women experience premenstrual dysphoric disorder. Estrogen appears to be involved in these mood disturbances, but exactly how is more of a mystery. Estrogen levels in women with PMS or PMDD are almost always normal. The problem may instead lie in the way estrogen "talks" to the parts of the brain involved in mood. Women with PMS or PMDD may also be more affected by the normal fluctuations of estrogen during the menstrual cycle. Having "the blues" after childbirth is so common it's considered normal. However, 10% to 25% of women experience a major depression within the first six months after childbirth. The abrupt drop in estrogen after delivery seems like the obvious culprit -- but this link has never been proved. Postpartum depression is treated like any other depression, with antidepressants, therapy, or both. Some preparations of estrogen do show promise as a potential add-on to these established treatments. In the months or years before menopause (called perimenopause), estrogen levels are erratic and unpredictable. During perimenopause, up to 10% of women experience depression that may be caused by unstable estrogen levels. Some studies suggest that using a transdermal estrogen patch by itself can improve depression during perimenopause -- but this is not a standard practice of care. Antidepressants were not given to women in these studies. At menopause, estrogen levels fall to very low levels. Interestingly, taking oral estrogen does not improve depression in women after menopause. In large trials evaluating hormone replacement therapy, women taking estrogen reported the same mental health as women taking placebo. After menopause, women's rates of depression fall, becoming similar to men of the same age.