Impaired Brain Development in Stressed Mothers and Offspring

Postpartum Depression (PDP) is a serious mental health problem characterized by a prolonged period of emotional disturbance, occurring at a time of major life change and increased responsibilities in the care of a newborn infant. According to a CDC survey, 11 percent to 18 percent of women reported having frequent postpartum depressive symptoms.

A new study on rats points to major complications and long-term effects of stress or depression in mothers. A normal mother rat displayed an increase in brain cell connections in regions associated with learning, memory and mood. Whereas the brain of the mother rat under stress throughout the period of pregnancy did not display such an increase.

The pregnant rats were exposed twice a day to stress by limiting their mobility on some days and on other days placing them in water. The animals showed classic signs of the effects of stress, including lower than normal weight gain and enlarged adrenal glands, a sign of high stress-hormone production. The mothers stressed during pregnancy also gave birth to smaller pups.

"And they were not very good mothers," said lead author Benedetta Leuner of Ohio State University. After separation from pups for 30 minutes, unstressed mothers would gather up their babies, put them in the nest and nurse them. Stressed mother rats left the pups scattered around, wandered around the cage and fed the babies less frequently. The stressed mother rats also exhibited more floating than unstressed rats in a water test; animals that float rather than swim are showing depressive-like symptoms.

"These findings in rats mimic some of the symptoms that are seen in women with postpartum depression," Leuner said.

The researchers primarily focused on the dendritic spines. These are the hair like growth that is seen on the brain cells that are used to exchange information with neurons.

Prior to this Leuner had conducted animal study that showed an increase of dendritic spines in new mothers' brains was associated with improved cognitive function on a task that requires behavioral flexibility. This flexibility made them more effective in multitasking.

"Animal mothers in our research that are unstressed show an increase in the number of connections between neurons. Stressed mothers don't," said Leuner. "We think that makes the stressed mothers more vulnerable. They don't have the capacity for brain plasticity that the unstressed mothers do, and somehow that's contributing to their susceptibility to depression."

"It's devastating not only for the mother, because it affects her well-being, but previous research also has shown that children of depressed mothers have impaired cognitive and social development, may have impaired physical development, and are more likely as adults to have depression or anxiety," she said. "A better understanding of postpartum depression is important to help the mother but also to prevent some of the damaging effects that this disorder can have on the child."

Leuner described the research during a talk on October 13 in New Orleans at Neuroscience 2012, the annual meeting of the Society for Neuroscience.