We know the answer to the question of nature or nurture when it comes to mental health: it’s nature and nurture. However, this is only the beginning of the story. In many cases, nature and nurture work together.
We can be confident that a child’s mental health is connected both to the genes they inherit from their parents (nature), and the environment they grow up in (nurture). However, in addition to this, parents’ nature (genetic variation) can affect how they nurture (socially influence) their child’s mental health. This is because the parents’ genes influence the parents’ behaviour, and their behaviour in turn creates the child’s environment. This concept is called “genetic nurture”.
Until recently, no studies had separated this genetic nurture effect from other influences on children’s mental health. However, this was made possible in the present study by the use of a large sample of 12,000 families from the Norwegian Mother, Father and Child Cohort Study (MoBa), plus a new analytical method called Relatedness Disequilibrium Regression (RDR). This allowed the team of researchers, which included a member of CoMorMent, to measure the effect of genetic nurture on children’s anxiety and depression symptoms at 8 years old.
When looking at anxiety, the researchers found that 5% of the children’s anxiety risk was linked to direct genetic inheritance, whilst none of the risk was associated with genetic nurture. However, the picture was different when looking at depression. Here the researchers found that genes that were inherited directly from the parents were responsible for about 19% of the children’s depression risk. A further 14% of the children’s depression risk came from the way the parents’ genes affected the children’s environment (genetic nurture).
Interestingly, the researchers found that a large portion of the depression risk from genetic nurture was related to mothers’ levels of anxiety and depression over their child’s early development. This could suggest that children are “learning” depressive behaviours from their mothers, though it’s important to remember that this is only one of many possible explanations. Mothers’ levels of anxiety and depression may well be reflecting other factors, such as domestic violence or social disadvantage. Future research should investigate this further. In the meantime, this work presents us with tentative evidence that reducing mothers’ anxiety and depression could help reduce children’s risk of depression.
