Washington, Oct 14 (IANS) Chronic stress during pregnancy negates benefits that the brain bestows on mothers and may explain why depression hits women after childbirth, says a study.
'Normal' rat mothers showed an increase in brain cell connections in the regions linked with learning, memory and mood. Conversely, the brains of mother rats stressed twice daily throughout pregnancy did not register this increase.
Researchers led by Benedetta Leuner, assistant professor of psychology and neuroscience at Ohio State University, were specifically interested in dendritic spines -- hair-like growths on brain cells that are used to exchange information with other neurons.
Previous animal studies conducted by Leuner at Ohio showed that an increase of dendritic spines in new mothers' brains was linked with improved cognitive function on a task that requires behavioral flexibility - in essence, enabling more effective multitasking, according to an Ohio statement.
The dendritic spines increased by about 20 percent in these brain regions in new mothers, according to her findings.
The stress in this new study negated those brain benefits of motherhood, causing the stressed rats' brains to match brain characteristics of animals that had no reproductive or maternal experience.
The stressed rats also had less physical interaction with their babies than did unstressed rats, a behaviour observed in human mothers who experience postpartum depression.
"Animal mothers in our research that are unstressed show an increase in the number of connections between neurons (brain cells). Stressed mothers don't," said Leuner.
These findings were presented at the annual meeting of the Society for Neuroscience 2012 in New Orleans, US.