London: In a discovery that could lead to a possible treatment to prevent post natal depression, scientists claim to have found the answer to what actually triggers the baby blues.
Shortly after giving birth to their babies, nearly three quarters of new mothers feel down and complain of sadness, mood swings, anxiety and loss of appetite -- the condition is classed as post-natal depression.
Now, scientists at the MPI for Human Cognitive and Brain Sciences in Leipzig, Germany, found that a sharp drop in oestrogen levels after birth releases an enzyme in the brain which blocks "feel-good" chemicals, the Telegraph reported.
Julia Sacher, who led the study, said: "Our results have the exciting potential for prevention for severe postpartum blues. This could have an impact on prevention and treatment of postpartum depression in the future."
Previous research has shown that in the first three to four days after giving birth, oestrogen levels drop by up to 1000 fold.
But the latest study found that in proportion to this oestrogen loss, levels of an enzyme called "monoamine oxidase A" increase dramatically in the brain.
This enzyme can break down serotonin and dopamine, which are known to cause contentment. If levels of these are low, it can lead to a risk of becoming depressed, the researchers said.
In their study, which followed 100 women as they went through pregnancy and recent motherhood, Sacher and her team found that levels of the enzyme in women who had just given birth were 43 percent higher than those in a control group.
The levels peaked on the fifth day after birth -- the day new mothers often hit their lowest point low, the scientists said.
Certain drugs can be used to lower levels of this enzyme, and also to increase levels of the chemicals it breaks down, they added.
The findings came after earlier studies suggested that women could be screened for post-natal depression while they are still pregnant.
In 2008, researchers found that women who gave birth to boys were more likely to go on to develop post-natal depression than those who had girls.
The condition is thought to affect more than one in ten new mothers, of whom two in 1,000 suffer the most serious form, called puerperal psychosis, in which they can develop delusions or hallucinations.
The new study has been published in the journal Archives of General Psychiatry.