More than 300 million people worldwide at any given time use hormonal contraceptives for a plethora of reasons: as birth control, to manage menstruation symptoms, to improve acne, and to treat endometriosis, among others. For up to 10 percent of women, however, hormone contraceptives can increase their risk of depression. In a piece for The Conversation, neuroscientist Natalie Tronson explains how hormone contraceptives affect your mood, for better or worse.