Two genetic variations linked to post-natal depression

Two genetic variants thought to be involved in the stress response have been linked to post-natal depression.

Researchers examined the genes related to the stress response in 140 women and measured symptoms of depression during pregnancy and after birth. They found two genetic mutations which they believe could provide the basis for a genetic test to identify which women are most at risk.

'This is extremely important because there is evidence if you can identify women at risk early, you could treat early or introduce measures early in order to stop the process of the disease', said Professor Dimitris Grammatopoulous, who led the research.

Previous studies have shown that the hormones regulating stress are disrupted during pregnancy and childbirth. This disruption is thought to make new mothers more likely to develop depression. The team, from the University of Warwick and the University Hospitals Coventry and Warwickshire NHS Trust, studied gene variants in two genes involved in the stress response: the glucocorticoid receptor (GR) and corticotropin releasing hormone receptor 1 (CRHR1) genes.

Two single nucleotide polymorphisms (SNPs), single letter changes, in the CRHR1 gene were associated with a slightly increased risk of post-natal depression symptoms. One of these two SNPs was also associated with increased depressive symptoms in pregnancy, suggesting it does not increase the risk for post-natal depression specifically. Women who had SNPs in both the GR and CRHR1 genes had the highest chance of showing increased depression symptoms.

Although the results are interesting, the study has some important limitations. As the authors explain in their paper, their study was underpowered: they did not include enough women to identify differences between the two gene variants and risk of depressive symptoms. To do that, they should have included at least 594 women.

Importantly, the authors did not include many other risk factors in their analysis. They excluded women who had a pre-existing mental illness, and didn't assess how well the gene variants predicted post-natal symptoms compared to some more established risk factors.

One in seven women experiences postnatal depression, and these gene variants could improve early identification of women at risk of becoming depressed. However, contrary to some newspaper headlines, a larger study is needed first to confirm the findings before they can be used as a postnatal depression test.