Childhood environment and intergenerational transmission of depression

Plant and colleagues, in a very interesting and elegant study, ¹ found that maternal depression during pregnancy was associated with: offspring depression in adulthood (odds ratio (OR) 3.4), maternal depression during offspring's childhood (OR = 4.8), and offspring exposure to child maltreatment (OR = 2.4). However, as the authors said, ‘when childhood factors (i.e. child maltreatment, maternal depression 1–16 years) were entered at the second steps, prenatal maternal depression no longer predicted significantly offspring depression’. In our view, these findings are suggestive that the key causal factor is not maternal depression during pregnancy, but maternal depression during offspring childhood and child maltreatment (probably the former promoting the later). Since maternal depression during pregnancy probably does not directly cause child maltreatment or later maternal depression, these two should not be viewed as mediators or mechanisms of the association found between maternal depression during pregnancy with offspring depression in adulthood. Since after adding the childhood factors there is no statistical correlation of maternal depression during pregnancy with offspring depression in adulthood anymore, this seems suggestive that maternal depression during pregnancy is more probably a marker of mothers with higher risk of developing depression during offspring childhood and of offering/allowing maladaptive parental behaviour. This is in line with previous studies showing that environmental factors, especially maladaptive parental behaviour, were total or partial mediators of the association between parental and offspring depressive symptoms. ^2–4 Despite maternal depression during pregnancy being a marker of an at-risk mother–child dyad, the actual causal factors seem to be the factors happening during childhood: maternal depression and parental behaviour. So, preventive measures should focus on screening mothers with depression (during pregnancy, but especially during offspring childhood), providing treatment and support for adequate parental behaviour.

However, the authors' conclusions go in the opposite direction. In the paper's discussion, it is stated ‘we did not find that exposure to maternal depression after birth contributes to this association (maternal depression during pregnancy with offspring depression in adulthood). This suggests that exposure to maternal depression specifically during pregnancy represents a unique setting for the intergenerational transmission of risk for depression’. However, the results section states ‘offspring exposure to maternal depression during childhood (1–16 years) was associated significantly with offspring adulthood depression (OR = 4.2)’. They see their study ‘in line with the theoretical premise of fetal programming’, related to elevated levels of maternal glucocorticoids at the intrauterine environment. Finally, for preventive measures, they emphasise screening and treating expectant mothers with depression, supporting the use of antidepressants during pregnancy. These are valuable measures, but not supported by this study results.

In summary, in our perspective, this extremely well-done study supports the view that childhood factors (parental behaviour and maternal depression) have key causal implications on intergenerational transmission of depression. Preventive measures should focus mainly on childhood, providing treatment and support for adequate parental behaviour.