Premenstrual syndrome (PMS) is a condition familiar to many women. It is estimated to affect between 20% and 50% of women of reproductive age. Also known as ovarian cycle syndrome or premenstrual tension, it's defined as a set of symptoms (e.g., moodiness, bloating, breast tenderness) that comes on a few days before the start of a menstrual period. Unfortunately, PMS is poorly understood.

Different women will experience different PMS symptoms, and not every woman experiences PMS. For some women, PMS may cause major discomfort and even disrupt normal activities. Some are totally unaffected and feel perfectly fine during the days leading up to menstruation.

Other women (roughly 5%) may have a more severe form of PMS called premenstrual dysphoric disorder (PMDD). Women with this form of PMS may suffer severe depression, anger, or low self-esteem along with other symptoms.

Women's menstrual cycles are controlled by a complex interaction of female hormones. These hormones help initiate menstruation during puberty, determine the rhythm and length of menstrual periods during childbearing years, and signal the end of menstruation at menopause. Hormonal control of menstruation involves the brain, pituitary gland, and ovaries.

The exact cause of PMS is unknown. It's thought to be related to changes in the level of specific hormones. A few studies suggest that PMS symptoms are linked to premenstrual fluctuations in a brain chemical called serotonin and increased sensitivity to the hormone progesterone. Other studies suggest that the hormone estrogen causes fluid retention, which probably explains the temporary weight gain, breast tenderness, and bloating experienced by many women with PMS. Recent research suggests that women with PMS may metabolize progesterone differently. Other hormonal and metabolic changes may also be involved, but further research is needed.

Other possible factors that may be associated with PMS symptoms include:

• lack of certain vitamins and minerals, such as calcium and magnesium
• eating a diet that is high in salty foods
• drinking alcohol or caffeine
• family history

If you suffer from PMS, you may experience different types of symptoms than your mother, your sister, or a female friend. Even if your symptoms are the same as someone else's, you may experience them more or less intensely. Your symptoms may vary from menstrual period to menstrual period and may change over the years. For some women, symptoms are intense but short-lived. Other women have to interrupt their normal routines because of the symptoms they experience.

Symptoms can last anywhere from a few hours to 2 weeks before the start of a menstrual period, with an average duration of 6 days per month. They usually start to go away when your period begins. In women close to menopause, symptoms may continue through and after a menstrual period. Some women go on to have painful periods after experiencing PMS. Teenage girls, for example, often have very painful periods after PMS, but this trend usually disappears as they get older.

PMS symptoms can be grouped into three categories:

Physical changes

• backaches
• bloating due to fluid retention
• breast tenderness, fullness, and pain
• changes in appetite (includes cravings for certain foods like chocolate)
• constipation or diarrhea
• difficulty falling asleep
• dizziness
• feeling of heaviness or pressure in the pelvis
• headaches or migraines
• hot flashes
• joint pain and swelling
• lack of energy
• nausea and vomiting
• severe fatigue
• skin problems such as acne or itching
• temporary weight gain
• worsening of existing allergies

Mood changes

• agitation
• anger
• anxiety
• depression
• feeling sad, hopeless, or overwhelmed
• irritability
• mood swings
• nervousness

Mental changes

• confusion
• difficulty concentrating
• memory loss or forgetfulness

Complications usually involve existing medical conditions that are made worse by PMS. Allergies or eye problems may be more severe, and women who have epilepsy may have more seizures than usual. Women who have lupus or rheumatoid arthritis may experience flare-ups during this time.

PMS is a condition that's largely self-diagnosed. This means that women tend to label themselves with PMS without actually seeing a doctor. Because PMS symptoms tend to reappear with every menstrual cycle, it becomes easy to recognize them. Those close to you may also notice differences in your behaviour.

A doctor may diagnose PMS if you tend to have many of the symptoms listed previously. The diagnosis of PMS includes a detailed history, checking for menstrual regularity, ovulation, and hormonal fluctuations, and in some cases looking for possible psychiatric disorders (such as depression).

It is often useful for women to chart their symptoms on a calendar to see if the symptoms are cyclical or last the entire month. This helps distinguish PMS from depression.