Depression in women is a complex biopsychosocial condition influenced by genetic vulnerability, brain chemistry, life stress, trauma, social factors, medical illness, and reproductive hormonal changes. Across the female life span, periods of major hormonal fluctuation—puberty, the menstrual cycle, pregnancy, the postpartum period, perimenopause, and menopause—are associated with increased vulnerability to mood symptoms in some women. Importantly, reproductive hormones do not “cause” depression in every woman; rather, some women appear to have increased sensitivity to normal hormonal changes, especially fluctuations in estrogen and progesterone. This hormone sensitivity can influence neurotransmitter systems, stress-response pathways, sleep, inflammation, and emotional regulation.The most clinically recognized hormone-related mood conditions include premenstrual dysphoric disorder, perinatal depression, postpartum depression, and perimenopausal depression. Public health and professional organizations emphasize that depression in women is common and treatable, and ACOG recommends screening for perinatal depression and anxiety at the initial prenatal visit, later in pregnancy, and during postpartum care. This article discusses the biological mechanisms, reproductive stages, clinical manifestations, diagnosis, prevention, and treatment implications of the relationship between depression and reproductive hormonal changes in women.