Babies born to depressed mums have higher levels of stress hormones, as well as with other neurological and behavioural differences, a University of Michigan-led study has found.
"The two possibilities are that they are either more sensitive to stress and respond more vigorously to it, or that they are less able to shut down their stress response," said lead investigator, Delia M. Vazquez, of the University of Michigan Medical School.
The analysis examined links between maternal depression and the development of an infants' neuroendocrine system, which controls the body's stress response, as well as moods and emotions.
At two weeks old, researchers found that the children of depressed mothers had decreased muscle tone compared to those born to mothers who weren't depressed, yet they adjusted more quickly to stimuli like a bell, rattle or light - a sign of neurological maturity.
"It's difficult to say to what extent these differences are good or bad, or what impact they might have over a longer time frame," said the study's lead author, Sheila Marcus.
"We're just beginning to look at these differences as part of a whole collection of data points that could be risk markers. These in turn would identify women who need attention during pregnancy or mother/infant pairs who might benefit from postpartum programs known to support healthy infant development through mom/baby relationships," she said.
The researchers recommended that mothers experiencing symptoms of depression during pregnancy talk to a therapist. They also noted that interventions aimed and mother-child bonding after birth can act as countermeasures, stimulating children's neurological development and lowering the possible effects of stress hormone production early in life.
Along with tracking the mothers' depressive symptoms throughout gestation, U-M researchers took samples of umbilical cord blood right after birth. They found elevated levels of adrenocorticotropic hormone (ACTH) in babies born to mothers with depression.
ACTH tells the adrenal gland to produce the stress hormone cortisol. Cortisol levels, however, were similar in children of mothers with varying levels of depression, likely an indication of the high level of stress associated with the birth itself, the researchers noted.
The study appeared in the journal Infant Behaviour and Development.