My childhood – Your childhood? Psychobiological consequences of maternal childhood maltreatment experiences in women and their children : An intergenerational study from late pregnancy to one year postpartum

Childhood maltreatment (CM) increases the lifelong vulnerability to negative mental and physical health outcomes, in particular when people encounter subsequent stressors – known as “second hits” – later in life. Alterations in the biological stress response system are discussed as an underlying mechanism, translating CM into negative health sequelae of stress. One highly relevant question in this context is whether this increased risk of behavioral, mental or physical health problems is transmitted to following generations. Altered biological imprinting during pregnancy could impact the development of the children of CM-affected women. The aim of this thesis was thus to investigate psychobiological consequences of CM within two generations – mothers and their children – over the first year postpartum. In a first step, this thesis considers risk and resilience factors that might contribute to a higher vulnerability to mental health problems in the postpartum period.

Study I explores the association of maternal CM experiences and psychosocial risk factors endangering maternal health during the postpartum period. Building on these find-ings, Study II investigates whether maternal CM exposure is associated with a higher maternal sensitivity to stress during the first year postpartum, contributing to a higher stress load and the risk of mental health problems. On the other hand, it is postulated that strengthening mothers’ resilience, e.g., through social support, could mitigate stress and help them cope with the demands of child care and the postpar-tum period. Hence, Study II additionally questions whether social support is indeed a protective factor during the first year postpartum, enhancing resilience against stress and thus might play a decisive role in maintaining maternal mental health. Completing the psychobiological perspective on CM consequences introduced in Review I, the third aim of this thesis is to examine longitudinal CM-related biological alterations in the endocannabinoid (eCB) system of mothers and children (Study III), to focus on the biological, intergenerational transmission of CM consequences. A total of 533 women were approached in the maternity ward of Ulm University Hospital shortly after parturition (t0: on average after M [SD] = 2.7 [4.8] days postpar-tum) and were accompanied over the first year postpartum, with follow-up meas-urements taken three months (t1) and twelve months (t2) after birth. CM exposure, mental health problems, social support and stress load were assessed in compre-hensive psychological interviews. Additionally, for eCB analysis, 3 cm hair strands were collected from mothers and children (t0 and t2), representing the last trimester of pregnancy and 10 to 12 months after birth. In a nutshell, this thesis shows that CM is associated with profound psychobiologi-cal alterations affecting psychological and biological functioning – casting a lifelong shadow on health and well-being. Study I shows that women with a history of CM face a higher burden of psychosocial risk factors in the already challenging postpar-tum period. Beyond this, Study II finds a CM-induced sensitization to stress: CM-exposed mothers exhibit a higher stress load, which contributes to more mental health problems and increases the risk that stress will more likely translate into mental health problems. While social support in general was not beneficial to post-partum women, social support from their partner proved essential to mothers’ men-tal health and helped them cope with postpartum challenges. Partner support has the potential to mitigate the effects of CM, reduces the maternal stress load and ul-timately protects the mother’s mental health (Study II). Completing the psychobio-logical perspective of early-life adversity, Review I identified CM as a principal cause for alterations in biological stress response systems that contribute to mental disorders.

Lastly, Study III shows that, during the final trimester of pregnancy, wom-en with a history of CM presented an altered eCB signaling that might contribute to greater inflammatory processes during pregnancy. As these alterations had van-ished one year after birth, Study III proposes that biological stress sensitization takes place: Having experienced CM does not necessarily induce alterations in the basal function of the eCB system, but rather alters its reactivity to stressors such as pregnancy. This thesis indicates that, at the same level of (psychobiological) stress, such as in pregnancy, CM-affected women may bear a higher physiological burden and may thus exhibit more negative health outcomes – such as more severe in-flammatory processes, more pain or complications during pregnancy – than women without CM. Most importantly, focusing on the intergenerational transmission of ma-ternal CM consequences: Study III shows that maternal CM exposure accounts for differences in infants’ eCB levels during late pregnancy, pointing to an intergenera-tional biological imprinting effect. However, all biological imprinting effects in the infants’ eCB system resolved within the first year after birth and there is as yet no evidence of persistent intergeneration biological transmission of CM within the eCB system. To summarize: The findings of this thesis enhance our understanding of CM as a lifelong psychobiological and even intergenerational vulnerability factor affecting two generations – mothers and their children. It provides new insights into the inter-play of psychological and biological risk and resilience factors that influence health and disease. This thesis clearly outlines new avenues for (i) scientific research and (ii) gives rise to promising practical implications for supportive interventions to en-hance maternal health and prevent an intergenerational cycle of adversity. Prospec-tively, future research needs to further investigate the regulation of the eCB system in utero and its relevance to pregnancy outcomes, as well as intergenerational ef-fects on the mental and physical development of children before and after birth. Moreover, it is hoped that this thesis will inspire the development and rigorous test-ing of supportive and preventive interventions to enhance mothers’ resilience dur-ing the postpartum period and beyond.