Most girls feel depressed and irritated before their periods. While most people dismiss it as nothing, the changes before a period are actually called premenstrual syndrome, or PMS.
PMS is caused due to a change in hormone levels, including estrogen, progesterone, and serotonin. Right before our periods, the level of serotonin decreases.
Serotonin is the hormone responsible for keeping you happy, so a decline in the levels of this happy hormone causes feelings of depression and sadness. The level of estrogen and progesterone also decrease prior to menstruation, which causes bloating and mood swings.
It is totally normal to feel some depression and mood changes before your periods, and the symptoms of PMS go away in a couple of days.
If you want to reduce these feelings, it is a good idea to exercise and meditate, as these activities increase the levels of serotonin and endorphins!