Scientists claim to have found out precisely why the commonly prescribed drug citalopram is effective in treating postpartum depression. New research suggests that the antidepressant may restore the connections between brain cells that are impeded by the effects of pregnancy-induced stress.

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Chronic stress during pregnancy is a predictor of postpartum depression.

The study, conducted by scientists from Ohio State University, examined the brain cells of rats that were chronically stressed during pregnancy. The research was presented at Neuroscience 2014, the annual meeting of the Society for Neuroscience.

The aim of the research was to identify the changes in the brain that may cause the symptoms of postpartum depression, focusing on an area within the brain that controls the reward system, known as the nucleus accumbens.

“We have a suspicion that stress during pregnancy is somehow altering the reward system in the brain, producing anhedonia and making these depressed mothers less rewarded by their offspring and less motivated to care for them,” says senior author Benedetta Leuner. “It’s possible that the effects of stress on the brain circuit regulating reward can lead to these symptoms.”

Postpartum depression, whereby new mothers experience a long-lasting form of depression, is a serious health problem that can have consequences for both the new mother and her family. According to the American Psychological Association (APA), an estimated 9-16% of new mothers develop the condition.

Although the symptoms of postpartum depression are distinct, experts are still uncertain as to what happens in the brain when mothers develop this condition.

Citalopram is a commonly prescribed drug for postpartum depression. It is a selective serotonin reuptake inhibitor (SSRI), a type of drug that promotes the amount of serotonin in the brain, helping the organ to send and receive neural messages, resulting in better and more stable moods.

Lead author Achikam Haim says the team found that citalopram was effective in improving the mood of stressed mothers and completely reversed the effects of stress in areas of the brain shown to be altered during pregnancy.

Dr. Leuner designed a rat model of postpartum depression in order to illustrate the changes that occurred in the brain. Depressive-like symptoms were induced in the rats by subjecting them to chronic stress during their pregnancy – a known predictor of postpartum depression within humans.

The rats would go on to exhibit symptoms shared by humans with postpartum depression. These included mood changes, deficits in caregiving behaviors and anhedonia – an inability to experience pleasure.

Within the nucleus accumbens, the researchers found stressed rats had fewer dendritic spines – small protrusions on brain cells that enable communication with other neurons – than unstressed rats. This deficit indicated a state of reduced flexibility or ability to adapt, referred to as reduced plasticity.

A similar result was found during research in humans that showed in mothers with postpartum depression; the reward center did not activate in response to hearing the sound of their child crying.

“The structural data from our work in rats can at least partially explain that, because neurons with fewer spines, and therefore less input, arguably have lower activation levels,” Haim said.

Citalopram was then administered daily for 3 weeks to the mother rats showing depressive-like symptoms, using mini-pumps implanted under the skin. This treatment led to a reversal in the changes that had been induced by chronic stress, returning the cells to their normal levels of complexity.

Although the antidepressants were found to be effective, the 3-week treatment timeframe is still problematic; it could be too long a timeframe with regards to a serious symptom of postpartum depression – poor maternal care.

Neglect that arises as a result of postpartum depression can have a lasting impact on the health of the child, potentially leading to an increased risk of depression and slowed cognitive and social development.

As a result, Dr. Leuner says that they the researchers will be looking at other neurochemical systems to target. “Fixing that impaired maternal functioning is really what’s critical in moving forward and developing better treatment options.”

Postpartum depression is not the only condition that recent research has found citalopram could be used for. A study reported on by Medical News Today found that the drug could also potentially be used to slow the onset of Alzheimer’s disease.