A future blood test might be able to predict which women will go on to develop depression after having a baby, new research suggests.

Researchers from Warwick Medical School found that women who develop postnatal, or postpartum, depression are more likely to have two kinds of genetic variants.

"Current screening policies rely on the opportunistic finding of PND cases using screening tools such as the Edinburgh Postnatal Depression Score (EPDS), but such tests cannot identify women at risk, ahead of them developing the condition," study researcher Dimitris Grammatopoulos, professor of molecular medicine at the University of Warwick, said in a statement.

But if this finding did eventually lead to a test that tells which women would develop depression before it happened, it could lead to earlier treatment for postnatal depression, researchers said.

The study, presented at the International Congress of Endocrinology/European Congress of Endocrinology, included 200 women who were pregnant. Researchers tested them for depression using the Edinburgh Postnatal Depression Score once before they had their baby, and again two to eight weeks after they had their baby.

The researchers found that women who went on to develop postnatal depression were also more likely to have gene variants of the glucocorticoid receptor gene and the corticotrophin-releasing hormone receptor-1 gene. These receptors are responsible for what goes on in the hypothalamo-pituitary adrenal (HPA) axis, which responds to stress.

Postnatal depression is more severe than just having the "baby blues" after giving birth, researchers noted. Symptoms include feeling irritable, withdrawn, agitated and worthless; feeling negative about the baby; disrupted sleep or irregular eating habits; problems concentration and working; suicidal thoughts; and feeling afraid to be alone with the baby or feeling inadequate at caring for the baby, according to the A.D.A.M. Medical Encyclopedia.

Treatments for postnatal depression may include taking antidepressants (there are certain kinds that won't be a risk to the baby if you are breastfeeding), going through counseling or undergoing hormone therapy, according to the Mayo Clinic.

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