Premenstrual syndrome (PMS) is the name given to the physical, psychological and behavioural symptoms that can occur in the two weeks before a woman's monthly period. It is also known as premenstrual tension (PMT).
There are many different symptoms of PMS, but typical examples are fluid retention, breast tenderness, mood swings, feeling irritable and loss of interest in sex (see Symptoms for more information).
Usually, these symptoms improve when the woman's period starts and disappear a few days afterwards.
A small number of women find that their symptoms are severe enough to stop them living their normal lives. This is due to a more intense type of PMS known as premenstrual dysphoric disorder.
Who is affected
Nearly all women of child-bearing age have some premenstrual symptoms, but those between their late 20s and early 40s are most likely to experience PMS.
Why it happens
The exact cause of PMS is not fully understood. However, it is thought to be linked to the changing levels of hormones in the body during a woman's menstrual cycle (see Causes for more information).
Outlook
There is no cure for PMS, but there are treatments available and changes that can be made to help women manage their symptoms (see Treatment for more information).
PMS usually improves after the menopause.
