Is it true that periods actually cause mood swings?

Certainly: The hormonal fluctuatoins can trigger mood swings commonly referred to as pms. About 30% of women report this. More severe and disruptive fluctuations are experienced in 8-10% of these women and is referred to as premenstrual dysphoric disorder (pmdd). Consulting with an ob/gyn is wise, as there are treatment options that can keep moods and life on a more even keel.