Freeman et al. (2004) controlled for variables including history of depression, age, premenstrual syndrome (PMS), poor sleep, hot flashes, race, and employment status, to help isolate where depressive symptoms during the menopausal transition might originate while accounting for variation in results. The study built on prior findings that the risk of major depressive disorder in women is highest during reproductive years due to ongoing hormonal fluctuation, and that estrogen administration had previously been shown to reduce depressive symptoms in women experiencing perimenopausal depression.