Abstract and Introduction
Abstract
In comparison with the vast epidemiological literature on postpartum depression (PPD), relatively few studies have examined the biological aspects of the disorder. However, research into the biological mechanisms of PPD is a challenging task, as normal pregnancy and the postpartum period cause adaptive endocrine changes, which would otherwise be considered pathological in nonpregnant women. This review focuses on the adaptive changes of childbearing and nursing, which ultimately may put women at increased risk of PPD. In light of the normal physiology, the authors also attempt to describe the current evidence of the biological changes associated with the development of depression in the postpartum period, including ovarian steroids, the hypothalamic–pituitary–adrenal axis, the serotonergic neurotransmitter system, the thyroid system and inflammatory markers. In addition, current knowledge on candidate genes associated with PPD is reviewed.
Introduction
Postpartum depression (PPD) is a condition strictly defined in the psychiatric nomenclature as a major depressive episode beginning within the first 4 weeks after childbirth. Considering the fact that many women may start experiencing symptoms later in the postpartum period, the definition is often extended to include the entire first year of postpartum. As with other major depressive episodes, the depressive symptoms must be present for at least two consecutive weeks, and in addition to the core symptoms – depressed mood or loss of interest in normal activities – sleep and appetite disturbances, loss of energy, feelings of guilt and suicidal thoughts may be present. This makes the PPD diagnosis a challenging one, since fatigue, changes in sleep patterns and weight changes are often observed in the normal postpartum period.
In the past, many risk factors for PPD have been studied. The emphasis has historically been on psychosocial aspects, such as a personal history of psychiatric illness (previous PPD being a highly significant risk factor),[1] low socioeconomic status, low level of education, alcohol and drug abuse, and low levels of social or partner support.[2,3] In addition, obstetric factors such as unplanned pregnancy, pregnancy complications and delivery modes have been debated as potential risk factors.[4] However, while these risk factors are important for PPD, the main targets of this review are the biological risk factors associated with PPD.
Biological theories on the pathophysiology of PPD are, to some extent, similar to those of other psychiatric disorders. However, postpartum women represent a specific group, with both hormonal and psychosocial events that have no parallel in a woman's life time. Therefore, a direct comparison between depression related to pregnancy and childbirth, and depression at other times during a woman's life cannot always be made.
Women's Health. 2012;8(6):659-671. © 2012 Future Medicine Ltd.
