Women may be cheery one minute and angry the next — but whatever mood they're in, you officially can't blame their periods.

Premenstrual syndrome, or PMS, may be an utter myth, according to new research from the University of Toronto. The study found that there was no obvious link between women's negative mood swings and the premenstrual phase of their cycles, according to a press release.

The university studied 41 research reports that tracked the change in women's moods throughout their periods, both before and during. Their findings showed no evidence that PMS itself even existed.

“There is so much cultural baggage around women’s menstrual cycles, and entire industries built around the idea that women are moody, irrational — even unstable — in the phase leading up to menstruation,” says Dr. Gillian Einstein, director of U of T’s collaborative program in Women’s Health in a press release. “Our review — which shows no clear evidence that PMS exists — will be surprising to many people, including health professionals.”

People have blamed mood swings on a woman's "time of the month" for years, with women dubbed irrational or emotional by men, friends or even themselves. A Glamour magazine poll found that 58 per cent of women blamed their periods for their emotional outbursts.

Recently, the stereotype of getting emotional while having your period has been challenged. Besides this U of T study, some companies like Kotex created satire tampon ads highlighting the stupidity of twirling around in your white spandex while menstruating. And earlier this week, feminine hygiene company BodyForm created a hilarious and sarcastic video response to one of their Facebook users, who'd found out the "ugly truth" of what a period was really like.

The university's research also found that out of all the reports that were examined, only six (or 13.5 per cent) showed links between negative moods and the premenstrual phase, Einstein added. The research also concluded that these reports in particular may be skewed for preconceived notions.

“Before women even get their first period, they have heard about PMS. The notion is so ingrained in our culture that some of these studies are actually biased because women know the study is about PMS,” says Einstein,

The research, however, did not touch on premenstrual dysphoric disorder (PMDD), a clinical disorder that affects the mood while a woman is on her period. PMDD symptoms are often more severe than mood swings in general and these may include depression, anxiety, insomnia, fatigue and headaches, according to Mood Disorders Association Of Ontario.

And even if PMS may not exist, cramps still do. At least 40 to 70 per cent of women feel some type of discomfort or pain when they're on their periods and this can include feeling bloated and losing energy.

Do you still think PMS exists? Let us know in the comments below.

LOOK: 10 natural ways to fight period cramps:

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  • Fresh Dill

    Fresh dill is packed with calcium and can add flavour to any bland salad or dip.

  • Sesame Seeds

    Nutritionist Kathy Smart says sesame seeds are packed with calcium and grounding them makes an easy paste.

  • Parsley

    Parsley is not only high in minerals and vitamin C, but when used in a tea, it can be a great way to help your body relax from aching.

  • Celery

    Smart says eating celery can also help fight fluid retention during your time of the month.

  • Salmon

    A plate of salmon is high in Omega-3 and helps fight inflammation.

  • Sacha Inchi Seeds

    Smart says sacha inchi seeds, a plant found in the Amazon, is rich in Omega-3.

  • Dark Chocolate

    If you're craving chocolate, make sure it's over 70 per cent cocoa. This bittersweet treat will help you relax your muscles.

  • Water

    We all know fluids are essential when your body is cramping or bloating. Smart recommends drinking two to three litres of water during your period.

  • Tea

    Tea is an easy way to replace your caffeine craving. Smart recommends green tea to soothe cramps.

  • Hummus

    Chickpeas are not only full of nutrients but eating hummus during your period can result in a <a href="http://www.3fatchicks.com/5-health-benefits-of-hummus/" target="_hplink">good night's sleep and uplift your mood. </a>

  • Avoid: Dairy

    Avoid getting calcium from dairy products, Smart says. Milks and cheeses can actually trigger cramps.

  • Avoid: Caffeine

    Caffeine is another no-no. Drinking lots of coffee or pop during your period can increase <a href="http://www.livestrong.com/article/96768-effects-caffeine-womans-menstrual-cycle/" target="_hplink">higher levels of tension and anxiety. </a>

  • Avoid: Too Much Sugar

    Excessive sugary foods, even when you're not menstruating, can also trigger cramps Smart says.

  • Avoid: Alcohol

    Smart says anything that can damage your liver should be off the list.

  • Avoid: Red Meat

    Red meat, Smart says, is also know to cause stomach upsets and cramps.

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