Most women are all too familiar with the I-just-want-to-go-home-and-put-on-my-sweatpants feeling that comes with their periods, but for some, symptoms like cramping, bloating and mood swings can be a lot more severe.

“My worst times I would spend locked in my closet, because I couldn’t stand the sounds of my kids or anyone talking to me,” Amanda LaFleur told The Huffington Post.

LaFleur, now 37 and a mother of two, has suffered from severe PMS symptoms since her first period at age 13 ― she was depressed, anxious and had suicidal thoughts. “The worst day was always ovulation ― and then it would be okay for about two weeks,” she said.

In her late 20s, the symptoms got worse. Bloating could add up to 10 pounds a day, but the worst effects were psychological, LaFleur said. The depression turned into bouts of hopelessness. Her anxiety worsened.

“I would have a hard time going to the store,” she said. “Sounds or anyone looking at me ― I couldn’t handle that.”

Doctors diagnosed LaFleur with premenstrual dysphoric disorder, or PMDD, a severe form of PMS with symptoms extreme enough to trigger disabling anxiety or depression and prevent women from going about their daily routines. An estimated 2 to 5 percent of menstruating women suffer from PMDD.

Birth control pills made LaFleur’s symptoms somewhat more bearable, but she went off the pills in her early 30s, when their side effects began to bother her and she was planning to start a family.

She suffered from postpartum depression after childbirth ― and a few months after that, her PMDD symptoms came back with a vengeance.

“Every single month, it felt like getting hit with postpartum depression all over again,” she said. That’s when the misophonia ― an extreme sensitivity to sound that can trigger anxiety, anger and rage ― got worse.

LaFleur’s doctors tried every treatment they could, from other forms of birth control to anxiety meds to antipsychotic drugs to drugs for bipolar disorder.

“I felt like people just threw things at me,” she said.

But now, new research suggests there’s a reason all those drugs didn’t work for LaFleur. A study published last month in the journal Molecular Psychiatry has identified a specific irregularity in the genes of the women with PMDD ― a difference at the molecular level that explains why their symptoms are so severe.

Marjan_Apostolovic via Getty Images The debilitating effects of PMDD affect as many as five percent of women who menstruate. A new study helps explain there may be a genetic reason why.

Women with PMDD are more sensitive to hormones.

Previous studies found that women with PMDD have a different sensitivity to the sex hormones they release when they’re menstruating ― and experts suspected that’s what caused the more severe symptoms, Peter Schmidt, chief of the Behavioral Endocrinology Branch at the National Institute of Mental Health and co-author of the new study, told HuffPost.

For this study, Schmidt and his colleagues compared 10 women who had been diagnosed with PMDD with 9 women who regular menstrual cycles and no PMDD. The women in the study with PMDD all experienced symptoms required for a diagnosis of PMDD.

Additionally, when the women with PMDD were given drugs to block the release of the sex hormones typically released during their periods ― estradiol or progesterone ― they did not experience the symptoms they would typically experience during their periods. The symptoms returned, however, when the researchers exposed the women to estradiol and progesterone.

The results confirmed that the women who experienced severe PMS symptoms definitely had PMDD and reinforced previous findings that PMDD is characterized by a unique sensitivity to the sex hormones released during menstruation, Schmidt explained.

When the researchers studied the cells of the women in the lab, specific gene networks known to play a role in how cells react to hormones were different in the cells of women with PMDD than in those of the women without PMDD ― both when the cells were exposed to estradiol or progesterone and when they were not.

The researchers also analyzed gene sequences of a larger group of women ― 34 who had been diagnosed with PMDD and 33 who had not, but who had regular menstrual cycles. Those analyses revealed the cells of women with PMDD in the larger group also had alterations in the same genetic networks.

“It’s the first evidence that this differential hormone sensitivity in PMDD is based on a biological difference that’s occurring on a cellular level,” Schmidt said.

Identifying the genes behind PMDD is the first step to better treatment.

While the women with PMDD may not immediately benefit from this research, it’s an important step forward in the effort to design new treatments for them, Schmidt explained. Better understanding of what causes PMDD and what distinguishes it from PMS may help researchers design better drugs and therapies for the condition, he said.

“Many women with this condition feel that it’s neglected,” Schmidt said. Either their doctors tell them it’s normal to be moody around their periods or they say it’s in the women’s heads, he explained.

Sometimes doctors prescribe drugs to help women suffering from PMDD to treat their anxiety, but those drugs don’t necessarily target what’s really causing the problem, Schmidt said.

“That people are studying and taking this condition seriously is very important to the women that have PMDD,” he said. “And that there is some biology or explanation for why their symptoms emerge ― that this is not just out of the blue ― is validating.”

LaFleur, who co-founded the nonprofit Gia Allemand Foundation for PMDD in 2013, deemed the new study “a blessing.”

“It validated that PMDD is not just women being overly emotional or not strong enough or not eating the right foods,” she said.

LaFleur eventually decided to have surgical menopause ― a full oophorectomy and hysterectomy ― in 2015, so she no longer lives with PMDD symptoms. The hope is that these new revelations will eventually lead to new and better treatments so other women don’t need to go to that extreme to avoid PMDD’s debilitating symptoms.

“Unless you’re in it, it’s really hard to understand how awful [PMDD] is,” LaFleur said. “That validation ― it was just everything we needed.”

This reporting is brought to you by HuffPost’s health and science platform, The Scope. Like us on Facebook and Twitter and tell us your story: scopestories@huffingtonpost.com.