Up to 75 percent of women struggle with PMS every month, say experts at Columbia University. “And premenstrual upheavals often take a turn for the worse -- or strike for the first time -- as women creep closer to menopause,” notes Mary Jane Minkin, M.D., a professor of obstetrics and gynecology at Yale University. The culprit: Erratic ups and downs in levels of the sex hormone progesterone, which disrupts the brain’s attempts to produce mood-boosting serotonin. Thankfully, Yale research suggests spending just 30 minutes outdoors each day -- whether you exercise, putter in the yard or just relax on a bench -- cuts even severe PMS-triggered anxiety, tension, and other symptoms in half. Turns out, the sun’s UV light stimulates brain cells to produce a steady trickle of symptom-taming serotonin, even when sex hormone levels are fluctuating wildly.