Many of us generally understand our periods. We sort of know when they will blow in like an unwelcome houseguest determined to destroy all of our underwear. But our moods around this time can be mysterious.

Studies show about half of women experience some mood disturbances around their periods, from grumpiness to cravings for hundreds of sticky buns. But, according to Dr. Samantha Brody-Meltzer, a psychiatrist from UNC’s Center for Women’s Mood Disorders, for between 2% and 5% of women, their periods actually cause clinical depression, known as premenstrual dysphoric disorder (PMDD).

“PMS, is the lay term, PMDD is for women who have a very severe version of it every month that really interferes with functioning and then goes away,” says Meltzer-Brody. “That is the main differentiation between women that have a menstrually related mood disorder and just depression. If you have depression, then your mood is down all the time. Most women with depression, it gets worse premenstrually, but you never return to a baseline where you feel fine. In contrast, women who have premenstrual dysphoric disorder get a clinical depression premenstrually, but after they get their period it goes away.”

So why is this happening, and when should you be worried? Here’s what you need to know about your hormones, reproductive related mood disorders, and premenstrual dysphoric disorder.

What is going on in your body:
During a normal 28-day cycle, day one is the first day of your period, and begins what is known as the follicular phase, when an egg ripens and is released. The luteal phase is the second part of the cycle. During this time, a milieu of hormones like follicle stimulating hormones, progesterone, and estrogen, are released. These hormones act like puppet masters telling your body what to do – and are the ones that will cause you to eat a tub of cookie dough ice cream. Then the egg is not fertilized, it is expelled and, of course, you have your period.

What this means for your mood:
In general, women have the same hormone expressions. Around day 14 of your cycle, high levels of estrogen, combined with surges in luteinizing hormones, and follicle stimulating hormones. Slightly later in your cycle, progesterone spikes. Depending on your individual sensitivities to these hormones, you react to them differently. “For people who have this dip in mood around ovulation, they are probably more sensitive to the spike in FSH, and luteinizing hormones leading up to ovulation,” Meltzer-Brody explains. “For a lot of women that have premenstrual symptoms after ovulation it is thought to be caused by high levels of progesterone.”

When to be worried:
Like many mental health concerns, the question is often how debilitating or frustrating are your symptoms. Some women report a down day, others are clinically depressed for the two weeks leading up to their periods. Meltzer-Brody suggests tracking your mood for a month, and speaking to your doctor if you are experiencing any of these symptoms. “If it is one bad day most people can put up with that,” Meltzer-Brody says. “But if you are talking about 2 weeks a month than that is 50% of your life, and that is bad.”

Why understanding your sensitivity to reproductive hormones is helpful over the long term:
For many women, hormonal sensitivity may affect them throughout their childbearing years and beyond. “You also see women that are very sensitive to the hormonal changes that occur around the period, can be sensitive to changes around pregnancy, postpartum, and perimenopause,” Meltzer-Brody says. “Some women just have more hormonal sensitivity. It may be limited to some particular time of their life, or it may be persistent across their entire reproductive life cycle.”

Ali works on the marketing team for LOLA. She's never met a dog she didn't like, and has a soft spot for BBQ. (Especially when it's followed by ice cream.)

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