Exposure to antenatal depression and childhood maltreatment

The association between antenatal maternal depression and offspring childhood maltreatment is a completely novel finding. The association between lifetime psychopathology in mothers and increased risk of childhood maltreatment in offspring has been described before – but never in the context of the perinatal period. Specifically, certain parental personality attributes have been associated with offspring maltreatment, such as low self-esteem, negative affectivity (depression and anxiety) and antisocial behaviours. ¹⁹ In a recent study, Kaplan et al ^{Reference Kaplan, Sunday, Labruna, Pelcovitz and Salzinger20} found that mothers of physically abused adolescents have more unipolar depressive disorders than comparison mothers. However, no other study, of which we are aware, has assessed maternal psychopathology in the perinatal period for mothers of maltreated children. Only Oliver, ^{Reference Oliver21} when describing a case series of 147 extremely complex families with multiagency involvement and a history of cross-generational childhood maltreatment, noticed that 7 (out of 147) mothers had been diagnosed with postpartum depression by their treating psychiatrist, but that all of them were rediagnosed at some point in later years as having a personality disorder. Our study therefore is the first methodologically sound, prospective study able to assess the impact of maternal perinatal psychopathology on the risk of the offspring being maltreated.

Our data point to a specific effect of antenatal, rather than postnatal, depression, in increasing the risk of childhood maltreatment. Indeed, the effect remains, even when we account for the fact that almost all the mothers who had depression in pregnancy went on to have further depressive episodes during their children’s lifetimes. Clearly, the mechanisms underlying this specific effect are as yet unknown, and further research on this is required. Indeed, a variety of pathways may explain this finding, including putative effects of antenatal depression on attachment, offspring temperament or a mother’s ability to protect her young from maltreatment by other family members. ^{Reference Misri and Kendrick22} However, it is important to highlight two key aspects of our results: first, our study does not suggest that mothers who have depression in pregnancy are more likely to be perpetrators of the maltreatment; and second, these analyses refer to women who had depression in pregnancy more than 20 years ago. It is possible that this association would be no longer present today, thanks to the increased emphasis on psychosocial support and treatment for women with antenatal depression. Clearly, this must be tested in more recent cohorts; but in the meantime, one can only continue to advocate assertive treatment of depression during pregnancy ^{Reference Pariante, Seneviratne and Howard23} and governmental support for Foundation Years services beginning in pregnancy. ^{Reference Field24}

Interestingly, our data are consistent with observations available from preclinical and clinical studies. Specifically, Champagne & Meaney ^{Reference Champagne and Meaney25} have observed that stress during gestation alters maternal behaviour in the rat by reducing pup maternal care (‘licking and grooming’) in lactating mothers previously characterised as expressing high levels of maternal care. It is of note that rat maternal behaviour is very stable, and this makes the impact of stress during gestation even more relevant. Moreover, lactating mothers who have been subjected to gestational stress also show a reduction of the brain expression of the receptor for oxytocin, a neurotransmitter regulating maternal care and social behaviour, which in turn may be due to a stress-induced increase in glucocorticoid hormones during gestation. ^{Reference Champagne and Meaney25} Consistent with these preclinical data, we have recently shown that depression during pregnancy is associated with increased levels of glucocorticoids, ^{Reference O'Keane, Lightman, Marsh, Pawlby, Papadopoulos and Taylor26} and another clinical study has shown that plasma oxytocin levels of women during pregnancy and the postpartum period are related to maternal bonding behaviours postnatally. ^{Reference Feldman, Weller, Zagoory-Sharon and Levine27} Therefore, it is possible to speculate that biological abnormalities induced by depression during pregnancy, such as elevated glucocorticoids, ^{Reference Pariante and Lightman28} may alter the oxytocin system and thus contribute to changes in maternal care. This biological pathway may be in addition to psychological and psychosocial pathways that could also affect maternal care and protection following antenatal depression.

Childhood maltreatment and child psychopathology

The relationship between childhood maltreatment and child psychopathology has been well documented, but all the evidence comes from studies in samples of children who have been abused. ^{Reference Kashani, Shekim, Burk and Beck29,Reference Famularo, Kinscherff and Fenton30} Indeed, large community studies have found less evidence of immediate and unavoidable effects of childhood maltreatment on child psychopathology. For example, in the Environmental Risk Longitudinal Twin Study, we found that, out of 82 children aged 12 years with experience of maltreatment in the family, only 13 (16%) had depression. ^{Reference Danese, Caspi, Williams, Ambler, Sugden and Mika31} There is also some evidence that childhood sexual abuse increases the risk of being a polysubstance misuser ^{Reference Shin, Hong and Hazen32} and of engaging in risky sexual behaviours ^{Reference Fergusson, Horwood and Lynskey33} in adolescence. Therefore, it is reassuring that in our prospective studies, as in other similar community ones, not all children exposed to maltreatment express frank psychopathology. We clearly show that the previous exposure to antenatal depression is indeed one of the moderating factors determining why some children do develop psychopathology when exposed to maltreatment.

Maternal depression, childhood maltreatment and child psychopathology

We find that it is really the co-occurrence of maternal depression and childhood maltreatment that leads to offspring depression and conduct disorder. Indeed, only exposure to both depression in utero and to maltreatment in childhood is associated with depression and conduct disorder in childhood and adolescence. This is also a completely novel finding. The association between lifetime maternal mental illness and child mental illness in offspring victims of maltreatment has been described before, but never in the context of the perinatal period, and usually in small case–control studies rather than epidemiologically based cohorts. For example, Kaufman et al ^{Reference Kaufman, Birmaher, Brent, Dahl, Bridge and Ryan34} reported that in 26 children with a history of maltreatment and of major depression, their first-degree relatives had approximately a ninefold increased risk for major depression and a three- to ninefold increased risk for other disorders such as antisocial personality, alcohol and substance dependence. Similarly, De Bellis et al, ^{Reference De Bellis, Broussard, Herring, Wexler, Moritz and Benitez35} in a case–control study of 53 children from maltreating families referred to a clinical service for post-traumatic stress disorder, showed that mothers of maltreated children exhibited a significant lifetime incidence of anxiety disorders (58%, especially post-traumatic stress disorder), mood disorders (72%, indicating major depression and dysthymia), and alcohol and/or substance misuse or dependence disorder (32%). The majority of the children (72%) had comorbid diagnoses involving both emotional and behavioural regulation disorders. ^{Reference De Bellis, Broussard, Herring, Wexler, Moritz and Benitez35} Because our data point to a specific effect of antenatal depression in increasing the risk of offspring maltreatment, it is tempting to speculate that the association between lifetime maternal mental illness and childhood psychopathology in offspring victims of maltreatment described in these studies may indeed be due to maternal mental illness already active in the antenatal period. However, none of these studies has addressed this hypothesis.

Other potential confounders

We began our introductory argument by describing the importance of potential confounders when examining the association between two variables. Therefore, having clearly demonstrated the moderating effect of childhood maltreatment in the association between exposure to antenatal depression and offspring psychopathology, we have also examined some other potential contributory factors – namely: the mother’s own experience of childhood abuse and her perception of an emotionally insecure childhood (both of which predicted maternal depression in pregnancy); current family instability (measured by the number of relationship changes that the offspring experienced during their lifetime); and the chronic nature of mothers’ depressive illness. Even after accounting for the potential confounders, the significant effect of the double exposure to maternal depression in pregnancy and maltreatment during childhood remained.

Limitations

The number of study participants is small and limited to a city population with high levels of social and economic deprivation and high levels of adolescent psychopathology. It is therefore difficult to generalise the findings presented here to other socioeconomic groups and geographical locations. Furthermore, although the prevalence rates of maternal depression in this community cohort are high, the low levels of other psychiatric disorders (substance misuse, personality disorders, post-traumatic stress disorder) preclude an investigation of their association with antenatal depression and childhood maltreatment, and of their impact on offspring psychopathology. In addition, the small sample size made it difficult to separate out the effects of harsh discipline, physical and sexual abuse, and to compare the effects on the offspring of maltreatment made by different perpetrators. Moreover, reports of sexual abuse at 11 years were limited to peer and sibling involvement of the child in activities for the purpose of their own sexual gratification, and it is unclear whether children who were still living with their parents would have reported sexual abuse. For example, when the 11-year-old child in the reported case history (Appendix) was asked whether he had been sexually abused, he replied that he did not know. Only when we interview the offspring as adults will we be able to see whether the reports of sexual abuse made as children were reliable. Clearly, reassessing the offspring as adults will be fundamental to clarifying these doubts.

Implications

Our study has implications for both clinical and biological psychiatry. From a clinical point of view, our study supports the notion that exposure to maternal antenatal depression is important in the link between childhood maltreatment and childhood psychiatric disorder: both by increasing the risk of offspring maltreatment per se, and by increasing the risk of psychopathology in the offspring when maltreatment does take place. This should inform the still controversial decision-making process around the treatment of depression in pregnancy ^{Reference Chambers36} and give priority to psychological, psychosocial and parenting programmes aimed at reducing antenatal depression as a pathway to reduce child and adolescent psychopathology. From a biological point of view, the mechanism by which fetal exposure to maternal depression (and, in general, to stress in pregnancy) contributes to later offspring psychopathology is still not clear. We and others have described persistent biological abnormalities in adults with a history of childhood maltreatment, which may participate in the pathogenesis of adult major depression ^{Reference Heim, Newport, Mletzko, Miller and Nemeroff37,Reference Danese, Pariante, Caspi, Taylor and Poulton38} or of adult aggressive behaviour. ^{Reference Hart, Gunnar and Cicchetti39} However, if childhood maltreatment is associated with antenatal depression, then it is possible that some of these biological abnormalities are due to the antenatal depression, or to the ‘double insult’ perpetrated through exposure to both maternal depression in utero and to maltreatment in childhood, rather than simply to childhood maltreatment. Indeed, stress in utero in animal models, and antenatal maternal anxiety in clinical studies, has long-lasting effects on the biology of the offspring, some resembling those described in animal models of early trauma. ^{Reference Glover, O'Connor and O'Donnell40} Future studies should dissect how antenatal and childhood events differentially and concomitantly contribute to biological changes that put an individual on the trajectory to adult psychopathology.

Funding

The study was supported by the Medical Research Council UK, project grant numbers and awarded to the late Professor Channi Kumar, D.S. and D.H., the Psychiatry Research Trust, and the South West GP Trust. C.M.P. is funded by the Specialist NIHR Biomedical Research Centre for Mental Health, Institute of Psychiatry and South London and Maudsley NHS Foundation Trust, London, UK.