Premenstrual syndrome (PMS) is a name for the changes in mood, and some of the physical changes, that happen to you in the days before your period begins.
Premenstrual syndrome (PMS) can affect your physical and mental health across the days leading up to your period.
The exact causes are complicated — but they have something to do with hormones like oestrogen, progesterone, and serotonin.
Lots of people get PMS. PMS is a big problem for some people.