A simple blood check for newly discovered genetic variants associated with postnatal depression could help doctors identify which new mothers are at risk of serious emotional changes after giving birth.

"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 postnatal depression," study researcher Dimitris Grammatopoulos, of the University of Warwick, in the United Kingdom, said in a statement.

Approximately 14 percent of women who give birth acquire postnatal depression, which normally starts around two weeks after childbirth. The researchers are hoping to development of a simple, accurate blood test which checks for the likelihood of developing the condition.

"Current screening policies rely on the opportunistic finding of postnatal depression cases using tools such as the Edinburgh Postnatal Depression Score, but such tests cannot identify women at risk, ahead of them developing the condition," Grammatopoulos said.

Postnatal depression is a serious condition, the researchers say, and quite different from the "baby blues," which is 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" designed to engage the child's attention. This may lead to learning and emotional difficulties for the children in later life.

The study tested a group of 200 women for postnatal depression two to eight weeks after birth, and compared this score to their genetics. They found that the women who developed postnatal depression were more likely to have several specific genetic variants that control hormones activated in response to stress, a pathway in the brain called the HPA axis.

The finding appears 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.

"We believe that we have made a discovery with important clinical and social implications. If we can identify women likely to suffer from postnatal depression 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," Grammatopoulos said.

The study was presented at the joint 15th International Congress of Endocrinology/14th European Congress of Endocrinology, which took place in Florence, Italy on May 5 to 9, 2012.