Before my brothers and I even understood what a period was, we were well aware of the forces of my mother's menstrual flow. A typically kind and patient woman, she would, my father used to joke, turn into "a bear" once a month, every month.

She'd get angry, once breaking a pile of white plates on our black kitchen countertop. She'd become sad and short-tempered, and seem so utterly exhausted that she could barely speak by dinnertime. This would go on for a couple of days. Then — poof — she'd be back to normal.

Though I have no empirical proof that these bursts were menstruation-related, their cyclical nature and my father's comments left me with a very strong impression. "Your mother's going to be on the rag," he'd say. "Watch out." And he was right.

few women are willing to discuss PMS openly

I'm not sharing all this because it's fun or easy to discuss. I'm sharing this because PMS is a natural part of life that the overwhelming majority of women who menstruate experience in some form — even in cultures that are not aware of the disorder — and yet remarkably few ever talk about openly.

So to learn more about PMS, I combed through the literature and called up some experts. I was surprised when one reminded me, almost nostalgically, there was a time when women used to cloister themselves in red tents during their menses. "If you think of all the things women balance, it was a respite, an opportunity to cherish their bodies and take care of themselves," said Dr. Barbara Levy, an obstetrician-gynecologist based in Washington, DC. "In the 21st century, PMS is just one more thing we have to deal with."

1) 75 percent of menstruating women experience PMS

"Premenstrual syndrome" is a collection of symptoms that up to 75 percent of menstruating women experience in some combination. It comes on during the "luteal phase" of the menstrual cycle, which spans the two weeks between ovulation and the first day of bleeding. And it takes many forms.

During this time, according to PubMed Health, some women feel a range of physical discomforts: abdominal pain and cramping, back aches, headaches, bloating, weight gain, breast tenderness, and sleeping and digestive interruptions. Even worse, perhaps, is the psychological distress: sadness, anxiety, irritability, lowered self-esteem, and an all-encompassing feeling of exhaustion.



The symptoms aren't the same for every woman, but again, many of us experience some combination of them. And the incredible part is that almost as soon as a woman's period begins, the symptoms in many cases vanish: energy levels bounce back, the aches, pains, and bloating go away, and mood lifts again.

An even smaller subset of women, about one in 20, experience even worse symptoms, particularly depression and anger. These women meet the criteria for a condition called premenstrual dysphoric disorder, or PMDD, which is now included in the Diagnostic and Statistical Manual of Mental Disorders. It's basically a very extreme form of PMS.

2) The causes of PMS are still a mystery — but it's probably not abnormal hormone levels



Really frustratingly, scientists still have no idea what causes PMS. For a while, researchers thought it might be abnormal hormone levels — though they've mostly moved away from that idea.

Hormone levels of women with and without PMS look very similar

"When you compare hormone levels of women who [experience PMS] to those who don't have this condition, they are virtually superimposable," said Dr. Peter Schmidt, a physician-researcher who has been studying PMS and PMDD for decades at the National Institutes of Health. There's no hormonal deficiency or excess in these women, even in the ones who have the most severe PMDD.

Still, both PMS and PMDD do seem to be linked to the menstrual cycle — and hence hormones — in some way. That's why Levy now describes PMS as "an abnormal response to normal hormones." In particular, the changes in hormones may send a signal to the brain that precipitates negative mood states. Again, why this happens for some is a mystery.

3) Some women have it much worse than others — and we don't know why



The million-dollar question in this area of research is a very basic one Levy alluded to above: why do normal changes in a woman's cycle affect some of us so severely?

When I asked the doctors about risk factors, they said researchers have looked at all kinds of things — exercise levels, history of depression or trauma, vitamin deficiency, body mass index, and of course hormone levels — and nothing seems to be predictive of whether a woman will experience PMS, PMDD, or nothing at all before their periods.



A few studies have found that genetics may play a role, so researchers are now looking at the interplay between environmental and genetic factors.

4) Diet and exercise can help PMS, but there's still no "cure"



As for how to treat PMS, evidence-based answers were frustratingly hard to come by here.

Some women find exercising on most days can be helpful, though the research in this area isn't particularly robust. There are studies that suggest antidepressant SSRIs taken only during the luteal phase of the cycle can reduce PMS symptoms, but this frequently comes with other side effects.

Some women find that using the birth control pill smooths out their cycles, but others don't respond to this treatment at all. There's some evidence that that dietary supplements pyridoxine vitamin B6, calcium, and chaste tree extracts may help relieve symptoms, according to PubMed health.

As a first line of treatment, though, doctors suggest doing all the things you'd normally do to stay healthy: eating a balanced diet, getting a good amount of sleep, avoiding too much alcohol, caffeine, and sugar, and exercising. But again, unfortunately, these practices don't minimize symptoms in all women.



So basically, there's no "cure" for PMS, which makes sense since we still don't even know exactly what causes it.

As for coping strategies, Schmidt said women have told him that logging their symptoms can be helpful. This way, they can remind themselves that it's their period coming and not the whole world and their bodies suddenly turning against them for no apparent reason.

5) Hormones are the reason people feel "bloated"



Researchers think that the bloating many women experience before their periods is caused by the hormone progesterone, which is mostly released during the second half of a woman's cycle.

This hormonal release causes the smooth muscles inside of you — including your intestines — to relax. "This allows for a lot of water to stay in the gut, so the gut dilates and that makes you feel bloated," explained Levy. "We feel fat because our bowels are distended."



It's also believed to be the source of pre-period constipation: since the smooth muscles of the intestines are involved in contractions, there's not as much motility when they're relaxed.

But there's the chicken-egg problem here, too. PMS may alter some women's perceptions of pain and discomfort, causing them to feel the bloating a little more severely than they normally would.

6) Strong carb and fat cravings before your period are normal

In the luteal phase of the cycle — again, between ovulation and the flow — some women start to eat more, and experience strong cravings for carbohydrates and fat.



Dr. Schmidt said he once met a woman with PMDD who would get her husband to drive her to Hershey, Pennsylvania, just so she could inhale the smell of chocolate.

But while the phenomenon is real, it's not clear whether this happens because women feel more tired or depressed or because there's something else going on in their bodies that's causing them to want more food. "These foods help people feel better briefly — they generally improve mood — so people seek them out when they’re feeling down," said Dr. Levy.

The same goes for the exhaustion, she added. "It's hard to sort out whether this is a bit of depression — fatigue is a hallmark symptom of depression — or whether it's something to do with hormones after ovulation."

7) PMS can be incredibly disruptive at work — but women find ways to cope

Dr. Schmidt told me that many of the women in his PMDD studies "occupy very high-functioning jobs." He's seen lawyers, politicians, diplomats, and doctors — women at the very top of their fields of work — live with the most severe forms of PMS.

These symptoms can certainly interrupt their lives, professionally and personally. At home, some women report blowout fights before their periods and a strong desire to simply retreat from the world and avoid their loves ones. "There's a huge repair job that goes on after," Schmidt said.

The worst form, PMDD, can be particularly disruptive. Women with this condition don't seem to enjoy the things they usually do, from seeing their friends or family to exercising, and even tasting foods they normally like. "Life events that were experienced as enjoyable and rewarding suddenly become sources of dysphoria and negative feelings," Schmidt said. "They start plummeting toward negative attention, negative bias, and that further complicates their symptoms."

Nonetheless, women find ways to cope with all sorts of crazy symptoms related to their periods. At work, they develop elaborate coping mechanisms: rescheduling court dates or cabinet-level meetings to avoid them overlapping with their PMS. So these women do really well — they have great jobs, spouses, families — but their symptoms can get in the way, and they have to find ways to minimize those interruptions.

Do you have other PMS or period-related questions we didn't answer? Or stories to share about your experience with PMS or PMDD? Write to Julia at julia.belluz@vox.com or find her on Twitter @JuliaofToronto.