Does mental illness run in families?

This article is adapted from the paper: Investigating Environmental Links Between Parent Depression and Child Depressive/Anxiety Symptoms Using an Assisted Conception Design (Lewis, Rice, Harold, Collishaw, and Thapar, 2011)

Here, we explore the factors that can lead to mental health issues in children whose parents have a mental illness. We’ll show that while genetic inheritance is often seen as the primary cause, it is not the only factor. We’ll also challenge the idea that children affected by parental mental illness will inevitably become unwell themselves.

Does mental illness run in families?

You’ve probably heard it said that mental illness runs in families.

We know from research that children with depressed parents are two to three times more likely to show symptoms of depression and anxiety than their peers.

It’s natural, therefore, to assume that children affected by parental mental illness are genetically predisposed to become unwell themselves.

However, we will demonstrate that this singular medical explanation is only half the picture. There is good evidence to show that the development of a mental illness is multifactorial, involving genetics and environmental factors.

This is good news because while genetic factors cannot be influenced, environmental stresses can.

With the right support, children affected by parental mental illness can be helped to develop resilience to reduce their risk of developing mental health issues in the future.

What factors can lead to mental illness in children?

Here we explore three possible factors that can lead to the transmission of mental health issues in children:

Genetics

Genetic factors refer to the idea of mental illness being inheritable.

Environmental

Environmental factors suggest children who experience parental mental illness become depressed and/or anxious because they live with the day-to-day impact of having an unwell mother or father.

Shared adversity

Shared adversity factors imply that children and adolescents become depressed or anxious because the whole family is struggling to cope with hardships such as poverty or bereavement.

How has this been tested?

Experts have tested these competing explanations by studying families with biological and adopted children, via twin studies, and thorough research on children born by assisted conception (IVF).

Some scientists think different genes might be responsible for depression in childhood versus adulthood, which makes the genetic connection difficult to measure.

Nonetheless, some clear patterns have emerged from the studies on twins, adopted children and IVF births.

What does the evidence show?

Adoption studies

Studies on adopted and non-adopted children find that both genetic and environmental factors play a role.

A study on the transmission of maternal depression found an association between both adopted and birth children. The link was greater for birth children, but still significant for adopted children — an impact that can only be environmental (Tully et al 2008).

A Finnish study demonstrated that children of mothers with schizophrenia, who were adopted, had an incidence of schizophrenia similar to those who stayed with their mothers. However, when good-quality relationships and family environment were present, the incidence of schizophrenia reduced to that of the general population. This suggests that a good environment can mitigate the increased genetic risk (Wahlberg et al 2004).

Twin and assisted conception (IVF) studies

In studies on the intergenerational transmission of depression, genetic factors emerged as significant in adolescence and for boys. For younger children (up to the age of 13), and for girls, environmental stresses proved more important.

This implies that young children are particularly sensitive to their parents’ wellbeing and that girls, in particular, are highly attuned to this.

The IVF study also explored shared adversity as a possible factor for the transmission of mental health issues from parents to their children. It concluded that shared adversity is not a leading cause for the transmission of depression symptoms (Lewis et al 2011).

Nonetheless, previous studies suggest it cannot be ruled out as contributing to the environmental link between maternal depression and child symptoms.

Summing up

The findings demonstrate that genetic inheritance is not the only cause of mental illness. A young person’s environment plays an important role too.

References

Lewis, G., Rice, F., Harold, G. T., Collishaw, S., & Thapar, A. (2011). Investigating environmental links between parent depression and child depressive/anxiety symptoms using an assisted conception design. Journal of the American Academy of Child & Adolescent Psychiatry, 50(5), 451-459.

Tully, E. C., Iacono, W. G., & McGue, M. (2008). An adoption study of parental depression as an environmental liability for adolescent depression and childhood disruptive disorders. American Journal of Psychiatry, 165(9), 1148-1154.

Wahlberg, K. E., Wynne, L. C., Hakko, H., Läksy, K., Moring, J., Miettunen, J., & Tienari, P. (2004). Interaction of genetic risk and adoptive parent communication deviance: longitudinal prediction of adoptee psychiatric disorders. Psychological Medicine, 34(8), 1531.