Major depressive disorders occurring during pregnancy and postpartum depression (PPD), collectively known as perinatal depression (PND), have a prevalence of 10–15 % in adult women [1–3] and are associated with significant morbidity to the mother, the newborn, and her family [4–7]. The prevalence of PND is significantly higher than both gestational diabetes mellitus and hypertension and incurs significant maternal/fetal morbidity and mortality. Depression during pregnancy is the single greatest risk factor for PPD [1, 8–11]. The point prevalence of major and minor depression occurring during pregnancy ranges from 8.5 % to 11.0 %, with data suggesting incidence rates of major or minor depression to be approximately 14.5 % [12]. Moreover, it is estimated that more than 60 % of PPD cases begin during pregnancy [8].

The literature consistently documents that maternal PND has multiple adverse consequences including maternal suicide and infanticide [13]. Depressed pregnant women are much less likely to engage in appropriate prenatal and postpartum care [14] and are more likely to engage in unhealthy lifestyle behaviors such as smoking and substance abuse and to make worse dietary choices [14–16]. In the postpartum period, maternal depression is associated with poorer maternal-infant attachment [13, 17] and parenting behavior that can have long-lasting adverse psychological consequences in the offspring [6, 7].

Screening for PND during pregnancy and postpartum can be readily accomplished with the use of a validated screening instrument. Table 6.1 describes commonly used instruments. One example is the Edinburgh Postnatal Depression Scale (EPDS), which is among the most commonly used and widely studied perinatal depression screening instruments in the world [12, 18, 23, 24]. The EPDS was specifically developed to assess PND and minimizes confounding of the somatic symptoms of MDD with parenting an infant (e.g., insomnia) [18]. Other depression screening instruments that have been used in the perinatal period include the Postpartum Depression Screening Scale (PDSS) [19], the Patient Health Questionnaire 9-item [20], the Beck Depression Scale (BDI) [21], and the Center for Epidemiological Studies Depression Scale (CES-D) [22].

However, despite the significant public health impact of PND, many risk factors have not been well described, including the relationship of maternal obesity and depression during pregnancy and postpartum. Obesity in the perinatal period is a complicated topic as there are a variety of clinical presentations. For example, some women come into the pregnancy already overweight or obese, while other women gain weight during the pregnancy that they are unable to shed in the postpartum period. In this chapter, we first review the literature on obesity and depression occurring outside of the perinatal period followed by a discussion of the studies investigating obesity and depression during the perinatal period.

Both major depressive disorder (MDD) and obesity are common public health concerns with up to 65 % of Americans meeting criteria for being overweight or obese [25] and 10 % of the general population meeting criteria for MDD [26]. Both of these conditions carry a high disease burden and increase the risk for mortality including via cardiovascular disease [27]. The question of whether MDD leads to an increased risk of obesity and, conversely, whether obesity leads to an increased risk of MDD is an important one as identification of high-risk populations for both of these conditions could lead to earlier and more targeted interventions and improved outcomes.

Over the past decade, research has provided more and more evidence of a link between the two conditions [28–33]. Cross-sectional studies provide a “snapshot” of the study population at one time point and allow determination of the risk for a condition in the setting of another. A systematic review of cross-sectional studies found “weak evidence supporting the hypothesis that obesity increases the incidence of depression outcomes” [34] and concluded that more prospective and longitudinal studies needed to be done. A more recent meta-analysis of community-based studies examined 17 studies with a total of more than 200,000 participants and found an odds ratio of 1.18, indicating that individuals with obesity were more likely to have depressive symptoms [35]. Interestingly, sex acted as a moderating factor, and the association was found only in women.

Cross-sectional studies do not allow insight into the direction of the relationship between two conditions. Longitudinal studies, on the other hand, though more difficult to conduct, allow researchers to determine if one condition leads to another and can provide insight into the mechanisms underlying the risk. A recent systematic review and meta-analysis of longitudinal studies on the relationship between depression, obesity, and being overweight confirmed a reciprocal link between depression and obesity [28]. They found that obesity at baseline increased the risk of the onset of MDD at follow-up with an unadjusted odds ratio of 1.55 (CI 1.22–1.98, P < 0.001) and that being overweight at baseline increases the risk for MDD with an unadjusted odds ratio of 1.27 (CI 1.07–1.51, P < 0.01). Thus, there appears to be a “dose–response relationship” in that the risk for MDD was larger in those who were obese as compared to those who were overweight. In contrast, baseline MDD did not increase the risk of being overweight over time, but increased the odds of being obese (OR 1.58, CI 1.33–1.87, P < 0.001) [28]. In contrast to the meta-analysis of cross-sectional studies, sex was not a moderator of the association.

There are several proposed mechanisms for the reciprocal relationship between obesity and MDD. MDD might increase the risk for obesity in several ways. People with MDD are more likely to engage in unhealthy lifestyles including smoking, unhealthy eating habits, and decreased exercise. MDD is also associated with dysregulation of the stress system [36, 37] that can lead to weight gain. Moreover, common symptoms of MDD predispose a person to gaining weight. For example, one of the specific criteria for the diagnosis of MDD is an altered appetite that can take the form of an increased appetite and overeating. In addition, MDD is often associated with decreased energy that can lead to decreased exercise and activity. Finally, most antidepressant medications are associated with some weight gain.

There are also several ways that obesity might increase the risk of MDD including both biological and psychological mechanisms. The hypothalamic-pituitary-adrenal axis (HPA axis) is dysregulated in both MDD [38, 39] and obesity [40, 41]; thus, dysregulation induced by obesity might trigger MDD. Weight gain and obesity have been shown to activate inflammatory pathways [42, 43], and inflammation is thought to play a role in MDD [44–46]. Obesity increases the risk for diabetes and insulin resistance, which could affect the brain in such a way as to increase the risk for MDD [28]. From a psychological perspective, obesity tends to be associated with decreased self-esteem, adverse childhood experiences, and teasing [36], which might increase the risk of MDD.

Regardless of the mechanism, it is becoming increasingly clear that the relationship between obesity and MDD is bidirectional in that obesity and depression are each causal factors for the other [28, 47]. Given the strength of this association, one would expect that obesity is a risk factor for PND and that depression during or after pregnancy would be associated with obesity or difficulty losing gestational weight gain. As the perinatal period represents a highly vulnerable time in a woman’s life, it is critical to understand other risk factors for maternal depression, including maternal obesity.

There are a number of factors that likely interact to influence the association between obesity and depression during the perinatal time. These factors include biological changes such as inflammation, HPA axis dysregulation, and the hormonal changes that are associated with pregnancy, labor, and delivery. Psychosocial factors including poor body image and poor self-esteem might also influence the risk of both obesity and depression. Previous research has demonstrated that there are very different attitudes towards eating behaviors and weight gain during pregnancy compared to postpartum [44]. Negative self-directed cognitions concerning eating, weight, and shape seem to be less pervasive during pregnancy and might be less likely to impact mood or anxiety [44]. Women might feel justified eating more during pregnancy, and weight gain is associated with nurturing a developing infant. In contrast, women are expected to lose weight during the postpartum period, and a failure to do so, coupled with a changed physique, could lead to negative cognitions that predisposes one to the development of depression. Lifestyle factors also play a role as many women decrease activity and have lower energy during pregnancy and postpartum. Sleep is often dysregulated, both during and after pregnancy, and a poor diet due to food cravings or the stress of becoming a mother can increase the risks for obesity and depression. A conceptual model of the relationships between obesity and depression in the perinatal period is depicted in Fig. 6.1.

The literature examining obesity and antenatal depression is small, and three studies document that obesity is not associated with antenatal depression [44, 48, 49]. In contrast, Bodnar et al. [50] reported a strong, positive dose–response association between prepregnancy obesity (based on BMI) and the likelihood of antenatal MDD. A major strength of this study compared to the previous literature, which generally assessed depressive symptoms, is the use of a structured clinical interview (the Structured Clinical Interview for DSM-IV Diagnoses or SCID), which allows a diagnosis of MDD to be made. The association of prepregnancy obesity with antenatal MDD remained after controlling for confounders and suggests that overweight mothers’ antenatal mood may be unaffected by the absolute amount of weight gained but is more robustly associated with the mother’s weight at the time of conception [50]. One possibility is that prepregnancy obesity leads to body image dissatisfaction or biological factors (inflammation, HPA axis dysregulation) that increase the risk of depression during pregnancy.

The literature assessing the risk of PPD among women who were overweight or obese prepregnancy is larger than that for antenatal depression. Most of these studies are small cross-sectional or longitudinal analyses [51]. Studies from Jenkin and Tiggemann [52] and Carter et al. [44] assessed depressive affect in the third trimester and again in the postpartum period, and both studies found significant associations between obesity and PPD. In contrast, a cross-sectional analysis from Vernon et al. [53] found no direct association between BMI and depression, but subjects with lower levels of physical activity tended to weigh more and to have more depressive symptoms, suggesting an indirect relationship between weight and depression.

Two studies from Lacoursiere et al. have also found significant associations between obesity and PPD [54, 55]. In an initial study of over 700 subjects [54], researchers examined depressive symptoms using the question “In the months after your delivery, would you say that you were not depressed at all, a little depressed, moderately depressed, very depressed, or very depressed and had to get help?” Patients who responded with “not depressed at all” or “a little depressed” were classified as not depressed, and those with any other responses were classified as depressed. Normal-weight women reported the lowest rate of moderate or stronger depressive symptoms (22.8 %), compared to underweight (27.7 %), overweight (24.8 %), and obese (30.8 %) women. The adjusted odds ratio for moderate or greater depressive symptoms among obese women was 1.53 (95 %, CI 1.15–2.02), and overweight and obese women were more likely to seek assistance for their depression than underweight or normal-weight women. In a follow-up study, Lacoursiere et al. [55] used a more rigorous and well-validated measure of depression, namely, the EPDS. They enrolled 1,027 women immediately postpartum and followed them for 6–8 weeks to determine whether prepregnancy BMI is associated with a positive PPD screen. Overall, the authors reported the lowest rate of depression among normal-weight subjects (14.4 %). Underweight (BMI <18.5), pre-obese (BMI 25–29.9), and class 1 obese (BMI 30–34.9) women had insignificantly higher rates of positive EPDS screens (18, 18.5 and 18.8 %, respectively). In contrast, significantly higher rates of depression were measured among obese class 2 (32.4 %, BMI 35–39.9) and obese class 3 (40.0 %, BMI 35–39.9) women. Consistent with previously described research linking obesity and major depression, prepregnancy BMI correlated with a history of depression. Additionally, the authors reported an association between BMI and a history of PPD, suggesting that obese women had an increased baseline risk for a positive EPDS, but a multiple logistic regression showed prepregnancy BMI to be an independent risk factor for PPD. Interestingly, women with a lower prepregnancy BMI were more likely to complete the study. Depressed women might be less likely to complete and return the EPDS. Therefore, the study results could underestimate the prevalence of depression among overweight and obese women.

In the largest study of which we are aware, Sundaram et al. [56] investigated the association between prepregnancy BMI and PPD. The authors extracted data on 45,285 women from the Pregnancy Risk Assessment Monitoring System, a national population-based survey. The authors assessed depression using a two-item questionnaire modeled on the PHQ-2, which is a brief clinical test to assess depressive symptoms. Their initial results indicated a 1.15-fold increase in the prevalence of PPD among obese (BMI ≥30) women (95 %, CI 1.023–1.302), but that effect was no longer significant after the authors controlled for maternal variables such as age, race, education, income, and pregnancy complications. Additionally, the authors found no differences in rates of PPD among under-, normal-, and overweight women (Table 6.2).