Maternal behaviour may transmit mental health problems to children
Mental health issues and the personality trait of neuroticism may be transmitted from parents to children. But does this transmission occur through genes or upbringing and environment? A new Norwegian study sheds light on the subject.
In recent years, studies have shown that mental health problems like anxiety, depression and substance abuse disorders are linked to a particular personality trait: neuroticism.
People with a high level of neuroticism in their personality worry easily. They often interpret people and experiences negatively and often have negative feelings and symptoms of depression or anxiety.
Previous studies have shown that neuroticism can be transmitted from parents to children. When parents have high levels of neuroticism, the risk of their children expressing both this personality trait and signs of emotional problems is greater.
Heredity and environment
However, such transmission can occur in several ways.
It’s well-known that genes are a big factor, both for neuroticism and mental problems. But it is also possible that parents influence their children through their upbringing and the environment they create in the home.
So how important are the various factors?
Helga Ask from the National Institute of Public Health and her colleagues at the Department of Psychology at the University of Oslo (UiO) wanted to investigate this. They have now used data from the Norwegian Mother, Father and Child Cohort Study to find out more.
The researchers looked at data from more than 11 000 sibling pairs in the parent generation, their partners and the couple's children when they were eight years old. The parent generation included full siblings, half-siblings and identical and fraternal twins.
By comparing all their data, the researchers were able to find out more about how much of the similarity in neuroticism and mental health problems in parents and children is transmitted via genes and how much must be due to something else.
More than genes
Ask gives an example of how the data material can provide new information.
Two sisters who are identical twins have exactly the same genetic make-up. When the sisters become mothers, all the children inherit half of these genes. Their children are thus just as genetically similar to their aunt as to their mother. But they grow up in two different homes, that is, in different child-rearing environments.
“If the child is more like the mother than the aunt, this suggests that the environment plays a role, Ask says.
Based on the data, the researchers have created a model for how neuroticism and mental health problems are transmitted between generations.
This model states that part of the similarity between parents and children is not due to genetics.
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Influence between mother and child
Simply put, the child's and mother's degree of neuroticism and mental health problems are a little more similar than genetics would suggest. This similarity appears to be due mainly to a direct effect between mother and child. No such connection between father and child was found.
Ask points out, however, that we cannot know what the influence consists of.
One possibility is that the mother's behaviour towards the child leads to insecurity and negative emotions. Another reason may be an unstable relationship between the parents that affects the child. It is also possible that the child learns the mother's behaviour and way of understanding the environment.
It is even conceivable that the connection is reversed, that is, that a child with numerous symptoms of mental issues affects the mother so that she also experiences more neuroticism and emotional challenges.
Mother’s responses weaken study
Svenn Torgersen, professor emeritus of psychology at UiO, was not involved in this research. He finds it interesting that the study is so large.
“The strength of the study is that multiple generations and relatives are involved,” he says.
“The weakness is that the mothers report on the children's personality and symptoms.”
The validity of the responses is diminished because the mothers answered the questions rather than the eight-year-old children. Mothers might perceive the child as more like herself than they really are.
Torgersen believes that this kind of bias could explain why it seems that the mother influences the child and the father does not.
The researchers describe this as a weakness as well.
“Maybe we would see the same effect with the father, if he had answered the questions,” Ask says.
Ask points out, however, that such a direct influence between parents and children is only a small part of the explanation for why the degree of neuroticism and emotional problems differ in children.
The rest is due to complicated interactions between genetics and the environment.
Studies have shown, for example, that the parents' genes can affect their children, even if the children have not inherited these particular genes themselves.
Genetics may contribute to impressing the parents' personality, which affects their parenting style, the relationship between mother and father and the atmosphere in the home. This can in turn affect the children.
And the matter is still complicated even when the children actually inherit these risk genes.
There is no one gene for neuroticism, anxiety or depression. Hundreds or thousands of genes work together and affect the risk of mental health problems in tandem with environmental influences.
Different genes in children and adults
Another issue is that the same genes do not always determine the risk of mental illness in children and adults.
“Some genes turn on or become more important over time. We know that a lot happens during puberty, for example. The mechanisms behind mental disorders in children and adults may be different,” says Ask.
Emotional challenges in eight-year-olds thus do not mean that the child will have mental health issues as an adolescent or adult, or that a contented child is guaranteed to have a life without mental illness as a teen and an adult.
Perhaps the new study would also have had different results if the researchers had conducted it when the children were older.
Unique reason for each individual
Previous research has also shown that the majority of the explanation for why an individual has mental health problems is the unique situation that each person finds themselves in.
The combination of our exact genetic composition and what we are exposed to in our family, at school and in our free time all factor into our unique lived experience.
“And this experience isn’t necessarily the same among siblings,” Ask says.
It could be that you have certain risk genes, combined with the fact that you lost friends because your family moved, or you have quite severe asthma and are bullied for this at school.
In other words, a lot of factors play into whether a child develops mental health problems. Some of these reasons are difficult to change.
However, if research confirms a direct influence between parents and children, this knowledge could be used to prevent mental health problems in children.
Ask and his colleagues have already applied for research funding to look for early signs of vulnerability. Providing parental support might help prevent these children from developing problems.
Torgersen believes it is too early to know the significance of Ask’s and colleagues' recently published results for treatment and prevention.
He thinks the new study does not weaken the results of previous studies that show that genetics play a major role in many types of mental disorders.
Genes are of great importance, especially for people who no longer live with their parents. Stable, chronic neurotic traits and stable anxiety and depressive symptoms are particularly strongly influenced by genetics, Torgersen says.
Helga Ask et.al.: Intergenerational transmission of parental neuroticism to emotional problems in 8-year-old children: Genetic and environmental influences. JCPP Advances, 2021.
The research article is part of the 'Intergenerational Transmission of Internalizing and Externalizing Psychopathological Spectra: A Genome-Wide Complex Trait Study' project funded by the Research Council of Norway.