Post-partum (or post-natal) depression is a condition that affects somewhere between 10 and 18% of all new mothers, and up to 35% of mothers with a history of mood disorders. It is characterized by feelings of anxiety, hopelessness, and sadness. Symptoms usually appear within four weeks of childbirth, and can last for up to a year, causing harm to mother and child.
What causes post-partum depression?
Until recently, it was unclear as to what exactly causes post-partum depression. The leading theory was that a sudden drop in estrogen levels after birth might be to blame; however, studies have found no significant difference in the levels of estrogen between women with and without the condition.
A new scientific paper, published in the online journal Molecular Psychiatry by researchers from the Johns Hopkins University School of Medicine, provides evidence to support the theory that post-partum depression could be linked to genetics, or more specifically, epigenetics.
Epigenetic factors are things that can affect the way in which a gene behaves, without changing the fundamental DNA sequence of the gene. Previous work on mice revealed that estrogen can alter the epigenetics of genes in cells in the hippocampus of the brain; genes that are thought to be involved with the creation of new hippocampal cells and the brain’s ability adapt to new environments. Both of these things are known to be important in the development of moods.
How was the study carried out?
From the mouse studies, two genes called TTC9B and HP1BP3, were identified as being possible targets for epigenetic change in hippocampal cells. To investigate whether this might also be true in humans, Dr Jennifer Payne, director of the Johns Hopkins Women’s Mood Disorders Center, took blood samples from 52 pregnant women who were already diagnosed as having mood disorders. The women were monitored throughout pregnancy and after giving birth to see who would develop post-partum depression.
What did the study find out?
Analysis of blood samples revealed that women who went on to develop post-partum depression after giving birth expressed stronger epigenetic changes in those genes most responsive to estrogen. According to lead researcher Dr Zachary Kaminsky, estrogen can act in similar ways to antidepressant drugs, so if its effects are inhibited in some way, as may happen when these epigenetic changes occur, this would make these women more likely to develop post-partum depression. As with mice, the TTC9B and HP1BP3 genes most strongly correlated with epigenetic changes.
What happens next?
The Johns Hopkins research team hope to continue their research and extend it to a larger sample of women with and without pre-existing mood disorders. They also hope to follow women and their children for a longer period of time to determine whether or not epigenetic differences in estrogen responses are hereditary. If further research is successful in validating these early findings, it is hoped that a blood test for predicting post-partum depression might be developed. This would allow mothers to identify whether they are at risk of developing this disease in order to manage it more effectively.