Researchers have shown that the babies of mothers dealing with anxiety or depression exhibit physiologically stronger signs of stress than babies of healthy mothers, when given a standard stress test.
These babies show a significantly increased heart rate, which researchers fear may lead to imprinted emotional stresses as the child grows up.
The interaction of mother and infant, especially in the early months of life, plays a huge role in healthy development.
Mothers suffering from mood disorders such as depression and post-natal depression, or anxiety, have difficulties regulating an infant's negative emotions, which is believed to create insecurities in the children as they grow older.
Irritability, changing moods and mild depression are common during pregnancy and the postnatal period, occurring in 10-20 percent of women.
"To our knowledge this is one of the first times this physical effect has been seen in three-month-old infants. This may feed into other physiological stress systems leading to imprinted psychological problems," said researcher Fabio Blanco-Dormond of the University of Heidelberg in Germany.
For the study, the research team recruited 50 mothers and their babies: 20 mothers exhibiting depression or anxiety disorders around the time of birth, and 30 healthy controls.
Each mother-baby couple underwent the Still Face Test. This test was devised in the 1970s. Mothers were asked to playfully interact with their babies, and then spend a period where they "blank" all interaction, before resuming normal contact.
Mothers were asked to play with their babies for two minutes, then cut off all interaction while maintaining eye contact.
After two more minutes mothers then resumed playful interaction. Throughout the test researchers measured the heart rates of both mother and baby.
"We found that if a mother was anxious or depressed, their baby had a more sensitive physiological response to stress during the test than did the babies of healthy mothers," the researchers wrote.
"This is a preliminary finding, so we need to repeat it with a larger sample to make sure the results are consistent. This is our next step," said Blanco-Dormond.
"This work means that it is important to diagnose and treat depressive and anxiety disorders in new mothers because it has an immediate impact on the stress system of the baby," the team noted.