Ladies, we all can relate to the feeling of being irritable, short-tempered and down and out during that time of the month. We may chalk our mood swings up to being stressed out, but in fact, it could be something deeper.

Before we start jumping to conclusions that our mood swings are more than just having a lot on our plate, or start using our temperamental shifts as an excuse to have a perpetual attitude, we asked Dr. Ayanna Miyako Walden, an expert in obstetrics, gynecology and infertility to fill us in on a topic that has become somewhat taboo to discuss: PMS.

From the time most of us near puberty, we started hearing the term PMS. Dr. Walden explains that Premenstrual Syndrome is characterized by physical and/or behavioral symptoms that occur repetitively in the second half of the menstrual cycle, often through the first few days of the period. "The symptoms can be severe enough to interfere with our daily lives and activities," says Dr. Walden.

PMS is very common and likely occurs in 75 percent of women with regular menstrual cycles. However, symptoms are only clinically significant in about 20 to 30 percent of women, meaning that while many women experience PMS, a smaller percentage experience it to a level that actually requires medical attention.

There is a lot of speculation surrounding PMS, and the exact mechanism within our bodies that causes PMS is unknown. This could explain why the topic is so seldom discussed amongst medical professionals - one doctor who was approached for this article said she hasn't commented on PMS in more that 20 years.

There are, however, studies that suggest what may be happening internally to trigger PMS. "All of the available studies suggest that PMS likely results from interactions between your ovarian hormones and your brain hormones - neurotransmitters like serotonin," says Dr. Walden.

Your ovarian hormones rise just before you ovulate, and near the middle of your cycle, they stay elevated and then drop dramatically just before your period, unless you become pregnant. "In studies of women with PMS, the women had hormones at normal levels. Thus, it is likely that PMS may just be an abnormal response to normal hormonal changes," Dr. Walden explains.

Contrary to what we may think, there aren't different levels of PMS. Severity is based on how much it interferes with daily life, and how incapacitating it can be for certain individuals.

Typically, a woman experiencing PMS may have abdominal bloating, extreme fatigue, breast tenderness and headaches. There are also common behavioral symptoms, like labile mood, irritability, tension, depressed mood, increased appetite, forgetfulness and difficulty concentrating. Other symptoms that can be more severe are heart palpitations, dizziness and gastrointestinal upset (nausea, vomiting, diarrhea). To get an accurate diagnosis, a physician may look at factors, like the timing with which these symptoms occur, severity and the exclusion of other diagnoses or medicine/hormonal ingestion.

Even with a solid list of symptoms to look out for, it is hard to tell the difference between PMS and just being straight-up stressed, especially since some of the symptoms are so similar.

"The symptoms are also similar to depression and other mood or anxiety disorders, as well as other medical disorders such as irritable bowel syndrome, thyroid dysfunction and chronic fatigue syndrome," says Dr. Walden. "However, a number of studies have demonstrated that stress may have little role in the severity of symptoms," she adds.

There are ways to get around the physical and mental effects of PMS. "There are a number of medications that can help, including antidepressants such as fluoxetine and oral contraceptive pills. Regular exercise may also help," Dr. Walden suggests.

If your symptoms feel more extreme than what we've mentioned, there is a deeper level of PMS called PMDD - Premenstrual Dysphoric Disorder - that neither exercise nor over-the-counter medications can help with.

PMDD is actually defined by the American Psychiatric Association DSM-IV. It is a more severe form of PMS and can be differentiated by the presence of multiple physical and behavioral symptoms that impair the patient's socioeconomic functioning for at least one week prior to a menstrual cycle and resolve within a few days after a cycle starts. "PMDD probably affects about only three to eight percent of the women with severe symptoms of PMS," says Dr. Walden.

The cause of PMDD is similar to the internal shifts that trigger PMS. The difference is that PMDD is generally controlled with medications, while PMS is usually not severe enough to need therapy. Can't tell if it's your mood swings or time of the month that are affecting your attitude? Take note of times you experience anything out of the ordinary and coordinate it with your cycle. If your symptoms are so intense that they interfere with daily life, you should check in with your gynecologist to see if you have PMDD.

What do you do to ease your premenstrual symptoms?