Premenstrual depressive symptoms and mood swings affect 3-8% of women in fertile age. The female hormones are believed to be the cause. Progesterone is well studied, but estrogen is not, and either are other causes such as intimate partner violence and chronic stress. The aim in this thesis was to investigate the influence of hormones as well as psychological aspects on the most common problems among women seeking care for premenstrual symptoms. In a cross-sectional study, four groups of women were included: ongoing users of oral contraceptives, with or without adverse mood symptoms and previous users, with or without experience of adverse mood. Depression and anxiety were significantly more common in both groups with reported adverse mood, in comparison with their control groups with no adverse mood. Self-reported PMS was significantly more common in those women who reported adverse mood, however, there was no difference in prospectively defined PMS or PMDD between the two groups of previous users. In a RCT with 25 women completing the study, GnRH treatment were tested in combination with two different HRT add-back doses of estradiol, in combination with progesterone and placebo. The higher dose of estrogen 1.5 mg in combination with progesterone induced significantly more pronounced symptoms than in combination with placebo. The lower dose, 0.5 mg gave less symptom recurrence in combination with progesterone. Exposure to violence was investigated among PMDD patients, healthy controls and gynecological patients. Among the participating women, gynecological patients, reported physical and/or emotional abuse significantly more often than did PMDD patients, as well as healthy controls. Chronic stress was investigated with diurnal cortisol, and low-dose dexamethasone test.  There was no difference in diurnal secretion of cortisol between PMDD patients and controls. No difference in the degree of dexamethasone suppression was found between PMDD patients and controls. According to the results from these studies, the main symptom provoking factor in women with PMDD appears to be the estradiol and progesterone fluctuations across the menstrual cycle, whereas chronic stress and intimate partner violence appears to be less relevant.