Prenatal stress in humans has been found to cause premature birth, low
birth weight, and problems with cognition and behavior.
One means by which prenatal stress unleashes these conditions may be by
thwarting the production, after birth, of nerves in the hippocampus region of
the brain. The reasons are because prenatal stress has been found to decrease
hippocampal nerve growth in both juvenile monkeys and adult rats and because
such nerve growth is thought to be involved in both cognition and
Thus, a crucial question is, Could the noxious effects provoked by prenatal
stress on hippocampal nerve growth after birth be reversed? Djoher Nora
Abrous, Ph.D., director of INSERM research at the Francois Magendie Institute
in Bordeaux Cedex, France, and her colleagues conducted an animal study to
find out and got an affirmative answer, as they reported in an article in
press with Biological Psychiatry.
They mated 43 female rats. Half were stressed each day from day 25 until
delivery. Stress consisted of restraining the pregnant females in cylinders
for 45 minutes, three times a day. The other half served as controls and were
left undisturbed throughout gestation.
After birth, half of the litters obtained from stressed mothers and half
from control mothers were raised by their mothers and left undisturbed until
weaning. The other half of the litters from the stressed mothers and control
mothers were also raised by their mothers until weaning, but were exposed to
an enriched environment as well. It consisted of 15 minutes of handling by
Then, after weaning, between 18 and 20 pups were selected from each of the
four groups for follow-up. The scientists then followed the four groups of rat
pups to determine whether prenatal stress had had an impact on hippocampal
nerve growth and, if so, whether an enriched environment (infant handling)
could neutralize the impact.
When the pups were 4 months old, the researchers found, hippocampal nerve
growth was similar for all groups except the one that had been prenatally
stressed but not handled. It had significantly less hippocampal nerve growth
than the other three groups had. Even more striking, results from when the
pups were 26 months of age suggested that such a reversal was maintained over
the entire lifespan.
The question now, of course, is whether the findings apply to humans.
"This study opens the door to the idea of being able to undo
biological changes that occur during fetal development through proper
intervention," Judy McKay, M.D., told Psychiatric News."
This is an exciting concept [and] has important clinical implications
for the possibility of developing appropriate interventions and treatments to
prevent some of the long-term effects of maternal gestational
McKay, a Columbia, S.C., psychiatrist, is also a member of APA's
Corresponding Committee on Infancy and Early Childhood.
"This study appears to show that the negative effects of stress
during gestation of rats can be reversed," Lois Flaherty, M.D., a Boston
psychiatrist and chair of APA's Council on Children, Adolescents, and Their
Families, commented. "The study needs to be replicated, but if it turns
out that it can be repeated with the same results in other laboratories, it
would have some important implications for how we might reverse the negative
effects of psychosocial adversity in humans."
The study was funded by INSERM (Institut National de la Sante et de la
Recherche Medicale) at the University of Bordeaux.
An abstract of "Postnatal Stimulation of the Pups Counteracts
Prenatal Stress-Induced Deficits in Hippocampal Neurogenesis" is posted