INTRODUCTION
Postpartum depression (PPD) is a psychiatric disorder, and one of the main complications of pregnancy, affecting between 10% and 20% of women in the year following delivery (1,2). PPD is a severe disease associated with short-term complications such as suicide, and long-term deleterious consequences, including depressive recurrence (2,3). It may also have negative effects for the child, including disturbances of early interactions (4).
Several types of PPD can be distinguished according to the onset of symptoms, severity and evolution (5–8). Studies over the course of several decades have consistently identified two distinct peaks of PPD: one early in the postpartum period and another later (9–12). Early PPD is usually defined as beginning in the first 6 weeks after delivery, while late PPD develops between the second month and the end of the first year postpartum (13–15).
PPD is a multifactorial disease. Some studies have reported sociodemographic and psychiatric risk factors, including extreme ages, primiparity or grand multiparity (more than 4 children), being single, and personal or familial psychiatric history (1,16–19). The strongest risk factor is a history of mood disorder (uni- or bipolar) (1,20,21). Other psychiatric disorders, such as addictive, anxiety, or personality disorders, are also considered to underlie vulnerability for PPD (17,19,22). Stressful life events are also associated with higher rates of PPD, whether they occur during childhood, adulthood or during pregnancy (1,23). Obstetrical factors, such as unwanted pregnancy, emergency cesarean section, or complications of pregnancy, are also associated with PPD (17,24–26).
While sociodemographic factors, psychiatric history, and stressful events have been individually described to be associated with postpartum depression, their contribution to the specific and independent influence on early or late PPD risk has not yet been characterized. Differences in socio-demographic factors or depression history were found to contribute to the onset timing of perinatal depression (pregnancy or postpartum), establishing different trajectories of depression (9,27). However, to the best of our knowledge, the distinction between early and late PPD has not ever been studied. In addition, very few studies considering PPD have a prospective design, making it extremely difficult to distinguish factors associated with early PPD from those associated with late PPD. While PPD is usually considered as a single disease irrespective of the time of onset of symptoms, our hypothesis is that factors may differ between early and late PPD. Indeed, the emotional and physical state of the mother as well as the environment that she finds herself in change between the first weeks postpartum and several months after birth (28). Mother-infant bonding evolves during the first year postpartum and changes the maternal emotional state; it seems important to determine the differences between these two time periods. A better knowledge of factors associated with early and late PPD is crucial to understanding different physiopathological mechanisms, and to better target women at risk.
We previously reported the prevalence of early and late PPD in a prospective study involving 3310 women evaluated at three times in postpartum, using face-to-face and telephonic interviews, as 8.3% and 12.9% respectively, resulting in one-year cumulative incidence of PPD of 18.1% (29). The aim of the present study is (i) to identify risk factors of early and late PPD among a wide range of variables including sociodemographic characteristics, personal and family history of psychiatric disorders, childhood trauma, and stressful life events during pregnancy, (ii) to assess the contribution of each of these risk factors to the development of early or late PPD.