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The exact cause of premenstrual syndrome (PMS) is not fully understood, but there are a number of possible factors that may contribute to the symptoms. These are described below.

Hormone changes

During your menstrual cycle, levels of hormones such as oestrogen and progesterone rise and fall. Hormone changes are thought to be the biggest contributing factor to many of the symptoms of PMS. The fact that PMS improves during pregnancy and after the menopause, when hormone levels are stable, supports this theory.

Chemical changes

Like your hormone levels, certain chemicals in your brain, such as serotonin, fluctuate during your menstrual cycle. Serotonin is known to help regulate your mood and make you feel happier, and so it is possible that women with low levels of serotonin are particularly sensitive to the symptoms of PMS. Low levels of serotonin may also contribute to symptoms such as:

  • tiredness,
  • food cravings, and
  • insomnia (difficulty sleeping).

Weight and exercise

Research has shown that you are more likely to have PMS if you are obese (a body mass index of over 30) and if you do little exercise.

Calculate your BMI here


You may find that your symptoms of PMS become worse the more stressed you are. While it is not a direct cause, being stressed can aggravate the symptoms of PMS.


Eating too much of some foods and too little of others may also contribute to the symptoms of PMS. For example, too much salty food may add to fluid retention and make you feel bloated, and alcohol and caffeinated drinks can disrupt your mood and energy levels. Low levels of vitamins and minerals may also make your symptoms of PMS worse.

view information about Premenstrual Syndrome on www.nhs.co.uk »

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