Depressed people tend to have too much of the hormone 'cortisol' in their blood.
Research suggests that prenatal depression can affect the developing fetus because maternal cortisol can cross the placenta. Tests show that fetuses and newborns have levels of cortisol in their blood and urine that reflect maternal levels. These findings highlight the need to monitor the psychological states of pregnant women to prevent cortisol from crossing the placenta and affecting the developing child. The brain scans of depressed mothers mirrored those of their infants. These babies responded poorly to the 'Brazelton assessment' - a test given to all newborns that analyses behaviours such as facial expression, movement and response to sound.