The discovery of specific genetic variants may lead to the development of a blood test to identify women at the most risk for developing postnatal depression.
About one in seven new mothers suffer from the condition, which normally starts around two weeks after childbirth.
“Current screening policies rely on the opportunistic finding of PND cases using tools such as the Edinburgh Postnatal Depression Score (EPDS), but such tests cannot identify women at risk, ahead of them developing the condition,” says Dimitris Grammatopoulos, professor of molecular medicine at the University of Warwick.
For the study, Grammatopoulos and colleagues assessed a group of 200 pregnant women for PND using the EPDS, once during their first visit to the prenatal clinic, and again two to eight weeks after they had given birth.
Women who developed PND were more likely to have specific genetic variants of the bcl1 and rs242939 single nucleotide polymorphisms (SNPs) of the glucocorticoid receptor and the corticotrophin-releasing hormone receptor-1 genes, respectively.
These receptors control the activity of the hypothalamo-pituitary adrenal (HPA) axis—an endocrine system that is activated in response to stress. The hypothalamus is part of the brain that monitors many aspects of the state of the body’s systems and is closely linked with the pituitary gland, which releases a number of hormones into the blood stream that control vital body functions.
Presented at the International Congress of Endocrinology/European Congress of Endocrinology, the findings appear to show that postnatal depression is a specific subgroup of depression with a distinct genetic element, which means that some women are genetically more reactive to the environmental factors which trigger depression.
“Although we knew already that there was an association of the HPA axis with depression, ours is the first study to show a link between specific elements of this pathway and the particular case of PND,” says Grammatopoulos.
“We now intend to conduct further research on other genetic variants of the HPA axis in a larger, multi-centre study involving women from Coventry, Birmingham, and London.
“We think that we have made an important step forward in characterizing the prospective risks and are therefore paving the way for timely, appropriate medical treatment for women who are likely to develop PND.”
PND is a serious condition, and quite different from the ‘baby blues’, which are milder and shorter-lived. Symptoms include sadness, changes in eating and sleeping patterns, crying episodes, reduced libido, anxiety, and irritability.
Effects on children can be significant; for example, depressed mothers are less likely to be affectionate towards and to play with their children and they may use less ‘baby talk’ which is designed to engage the child’s attention. This may lead to learning and emotional difficulties for the children in later life.
Although it may seem evident that PND is caused by some kind of hormonal upheaval but the role of the HPA axis in this form of depression has not been proved until now.
“We believe that we have made a discovery with important clinical and social implications,” Grammatopoulos says. “If we can identify women likely to suffer from PND in advance so that they can be treated appropriately and at an early stage, we will have improved the lives not just of the parents, but also of their children.”