The present study is the first to assess the association of maternal CM exposure with trajectories of child`s mental health measures in a prospective birth cohort. Our results add to the existing literature by a detailed trajectorial description on an annual base and a two-dimensional operationalization of maternal mental health burden by introducing maternal duration and strength of anxiety/depression symptoms in our models. The findings indicate that maternal CM is associated with more behavioural and emotional difficulties in children. While behavioural and emotional decreased in children of mothers without CM experience between the age of 4 and 7, this tended to be mitigated in children of mothers with CM experience. This was mediated by maternal symptoms of depression and anxiety. Male sex of the offspring was not only associated with more behavioural and emotional difficulties but also with higher maternal symptoms of depression and anxiety.
An association between maternal CM and child mental health was often shown [9, 14]. We add to this literature by focusing on trajectories of behavioural and emotional difficulties in the offspring. Overall behavioural and emotional difficulties decreased with age, an observation in line with findings from representative samples [23]. However, even being not consistently statistically significant in multivariate analyses, the difference between behavioural and emotional difficulties in children of mothers with and without CM experiences tended to increase with older age of the children. Significant differences in child SDQ for maternal emotional neglect and the sum of CM forms experienced by the mother at her child’s age 7 were shown. This finding is supported by a study based on prospective data of Finnish adolescents with increased differences in the risk for incident behavioural and emotional difficulties in dependence of maternal adversities with increasing age [24]. In contrast to these results assessed on an annual base, other literature does not reveal a moderating effect of child age. One reason may be the categorization of age into groups above and beyond the age of 8 years [14].
Interestingly, descriptive analyses found significant differences in behavioural and emotional difficulties in the offspring for maternal emotional neglect and the sum of experienced forms of CM. Similarly, in multilevel analyses, besides the sum of experienced forms of CM, maternal emotional abuse and emotional neglect significantly predicted behavioural and emotional difficulties in the offspring. The role of emotional abuse and neglect on the development of children is often neglected in clinics and research. However, research suggests even a higher effect of emotional compared to physical and sexual abuse [25]. Our results point towards an intergenerational effect of emotional abuse and neglect and underline the major importance of non-physical CM forms. However, although relative values are largely comparable to the general population [26], the total number of mothers who have experienced the different forms of CM in our sample was quite small.
The risk of individuals who have experienced CM to develop a psychiatric disorder is on average at least twice as high as the risk of non-exposed individuals [2, 27]. The effect we see on mental health of children is significantly lower which is in line with the literature [14], although longer follow-ups until adulthood are needed to ensure comparability. However, our data indicate that the effect of maternal CM is intergenerational.
Maternal anxiety and depression significantly mediated the association between maternal emotional abuse and neglect and child behavioural and emotional difficulties. Surprisingly, we found no significant association between maternal physical and sexual abuse and maternal symptoms of depression/anxiety which is in contrast to previous research [2, 4, 28]. This may be due to our relatively small sample size and the low proportion of mother who experienced sexual abuse.
Importantly, in our approach, symptoms of anxiety and depression were operationalized as “area under the curve”, thereby showing maternal internalizing problems during time course and not at one single time point. This is novel, taking into account not only severity but also chronicity of these symptoms and adds to the existing literature by combining these dimensions. Results indicate a dose-response relationship between the burden of maternal symptoms of depression and anxiety and child mental health. This shows the relevance of interventions at any time point, also beyond infancy and toddler age. Maternal mental illness negatively affects child mental health, but effective treatment of maternal depression is associated with a significant decrease in child psychiatric symptoms [13].
However, maternal mental health is only one route via which maternal CM may affect the mental health of the offspring. Possible other reasons for this intergenerational transmission comprise both, nature and nurture aspects at different development stages. Prenatally, changes in maternal factors in the oocyte or during pregnancy may impact child mental health [15]. Other postnatal CM-associated maternal factors are an enhanced risk for higher maternal stress, harsh parenting or perpetration of CM [9, 29]. Of note, these factors are strongly interrelated, as e.g., maternal mental illness is linked to higher maternal stress, and a higher risk of harsh parenting and perpetration of CM [30]. Further prospective studies across generations that comprise somatic and mental health are needed to disentangle this highly complex interplay of genetics, stress biology, mental health and parenting.
Interestingly, male sex of the child was associated with increased symptoms of anxiety and depression in mothers. Literature shows heterogeneous results for the interplay between maternal and child mental health and child sex [31, 32]. However, when maternal CM is taken into account, a greater vulnerability for boys was shown before for the indirect effects of maternal CM via anxiety and depression [33]. Our results point in the same direction. In our findings, older age and female sex were associated with lower behavioural and emotional difficulties, which is in line with the results of representative samples [23]. Sex is known to significantly affect the development of psychopathology, as there are relevant gender differences regarding mental health problems [34]. Child sex is further suggested to moderate the effect of maternal and child mental health [32].
A central limitation of the present study is that CM experience and maternal and child mental health are based on maternal self-report. Maternal rating of the child mental health might have been affected by CM experience and mental health with maternal depression resulting in overreporting of child mental health problems [35]. The time of the CM assessment might further be considered critical as a decline in recall accuracy was proposed suggesting that an earlier assessment might result in less memory bias [36]. However, underreports tend to be more frequent than overreports, i.e., those who were subject to abuse often provided false negative reports [37], which may result in to lower observed than true effects. A lack of distance to the experiences at a very young age might also be an issue [36].
Besides, as recruitment took place only at one site and in a relatively affluent city in the South of Germany, and selection bias due to stronger loss to follow-up of non-German families or families with a lower socioeconomic status cannot be excluded, our sample cannot be considered as representative for the German population. However, behavioural and emotional difficulties in our sample were comparable but slightly lower compared to those in the German Health Interview and Examination Survey for Children and Adolescents (KiGGS), a nationally representative survey including 14,835 children aged 3–17 years [23]. Rates of emotional abuse were slightly higher in our sample compared to a sample of the general population in Germany, while all other forms were lower, with significantly lower rates for physical neglect in our sample [26].
Overall, despite these limitations, the presented data provide an important first insight into the relevance of maternal CM on the trajectories of mental health in the offspring and highlight the importance of chronicity and severity of minor symptoms of maternal depression and anxiety in this interplay. Based on a somatically and psychologically well characterized prospective cohort, our study underlines the high complexity of the development of mental health problems in childhood and the necessity for comprehensive approaches to better understand the relationship between maternal CM, maternal mental health and child mental health. Furthermore, our results reveal a greater vulnerability of male gender in this interplay.
In sum, our results indicate that the association between maternal CM and child behavioural and emotional difficulties increases with older child age. Thus, further research with longer follow-ups up into adolescence and adulthood is needed. The here shown cumulative effect of symptoms of depression and anxiety on child mental health underlines the relevance of effective treatment for mentally ill parents.