Levels of a hormone called allopregnanolone could predict the likelihood of postpartum depression, according to new research published in the journal Psychoneuroendocrinology.
During the study, 60 pregnant women between the ages of 18 and 45 (all of whom had been previously diagnosed with a mood disorder) were observed by researchers at Johns Hopkins University.
Each participant took a mood test and gave 40 millilitres of blood during the second and third trimester of pregnancy. Of those, 45.3 per cent developed postpartum depression at between one and three months postpartum.
Using the blood samples, the researchers measured levels of progesterone and allopregnanolone, a byproduct made from the breakdown of progesterone and known for its calming, anti-anxiety effects.
The researchers found no relationship between progesterone levels in the second or third trimesters and the likelihood of developing postpartum depression. They also found no link between the third-trimester levels of allopregnanolone and postpartum depression. However, they did find a link between postpartum depression and diminished levels of allopregnanolone levels in the second trimester.
According to the study data, a woman with an allopregnanolone level of 7.5 nanograms per millilitre had a 1.5 per cent chance of developing postpartum depression. At half that level of hormone, a mother had a 33 per cent likelihood of developing the disorder. For every additional nanogram per millilitre increase in allopregnanolone, the risk of developing postpartum depression dropped by 63 per cent.
In a report on the study, the researchers say the findings could lead to diagnostic markers and preventive strategies for treating the disorder.
Because the study data suggest that higher levels of allopregnanolone in the second trimester seem to protect against postpartum depression, the researchers are hoping to investigate the possibility that allopregnanolone can be used as a preventative treatment in women at risk of postpartum depression.
Lauren M. Osborne, the study’s lead author, said: ‘Many earlier studies haven’t shown postpartum depression to be tied to actual levels of pregnancy hormones, but rather to an individual’s vulnerability to fluctuations in these hormones, and they didn’t identify any concrete way to tell whether a woman would develop postpartum depression.’
‘For our study, we looked at a high-risk population of women already diagnosed with mood disorders and asked what might be making them more susceptible. Every woman has high levels of certain hormones, including allopregnanolone, at the end of pregnancy, so we decided to look earlier in the pregnancy to see if we could tease apart small differences in hormone levels that might more accurately predict postpartum depression later.’
‘Postpartum depression (depression that occurs after the birth of a baby) can be devastating, with an estimated 20% of postpartum maternal deaths being thought to be due to suicide. This small-scale American study suggests that low levels of the anti-anxiety hormone allopregnanolone in the middle of a pregnancy may predict whether postpartum depression may occur, and that as a consequence potential prevention could be started in advance by using allopregnanolone as a treatment.
However, there are several caveats here to this potentially very interesting study. The numbers involved were extremely small, and larger scale trials are now needed to see if this finding is reproducible. Many of the participants in the study also developed postpartum depression whilst taking antidepressants or mood stabilisers – a contradiction that requires further analysis.
So, an interesting development but one which requires more intensive studies before fresh treatments become available for postpartum depression.’