Infant abuse can alter the brain, both animal and human experiments have
shown. Infant abuse may also be capable of altering genes in the human brain.
Postmortem examination of the brains of people who had had a history of early
childhood abuse or neglect and postmortem examination of the brains of people
who had not had such a history revealed reduced gene expression in the
hippocampus of the former, Patrick McGowan, Ph.D., of the Douglas Mental
Health University Institute in Montreal, Canada and colleagues reported in the
May 7, 2008, PLOS One.
Now researchers report something even more startling—that gene
alteration caused by infant abuse can be transmitted to the next generation,
at least in rodents.
The lead investigator of this new study was Tania Roth, Ph.D., a
postdoctoral fellow in neurobiology at the University of Alabama at
Birmingham. Results appeared in the May 1 Biological Psychiatry.
Roth and her colleagues used 14 rat pups for their first experiment. Half
were exposed to a stressed, abusive mother for 30 minutes daily during the
first postnatal week, and the other half to a positive caregiving mother
during the first postnatal week. This means that the first group was roughly
handled or actively rejected by their mothers, whereas the latter group was
licked, nursed, carried around, or otherwise positively handled by their
After the rat pups became adults, the researchers conducted postmortem
examinations to see whether there were any differences between the brains of
the maltreated rats and the brains of the control rats as far as the
expression of brain-derived neurotrophic factor (BDNF) gene was concerned.
This gene makes a protein that stimulates nerve development in the brain, and
it seems to be involved in a number of mental illnesses (Psychiatric
News, December 7, 2007).
The researchers found changes in the methylation of the BDNF gene and in
turn changes in BDNF gene expression in the prefrontal cortex of the
maltreated animals but not in the control animals.
The researchers then focused on five of the female rats that had been
maltreated as infants and looked to see whether they maltreated their own
offspring. They did. The researchers also discovered that these offspring had
the same BDNF gene methylation in the prefrontal cortex that their mothers had
had. So it looks as if the female rats had not only passed maltreatment on to
the next generation, but that this transmission may have been at least
partially via methylation of the BDNF gene.
At first glance, it may seem rather improbable that one generation's life
experiences could be transmitted to the next generation genetically. However,
the experiments that Roth and her team conducted are part of an emerging field
of science called epigenetics, which has shown that not just life experiences,
but diet, alcohol, nicotine, and some other environmental factors can alter
genes in the brain. Such alterations are often caused by methylation, in which
a methyl group attaches to the control segment of a gene and either silences
the gene or activates it without altering its genetic code. This was the case
in the BDNF gene abnormalities that Roth and her group observed.
"Our results highlight a molecular mechanism that helps explain the
far-reaching effects of child abuse and neglect on brain function and
behavior," Roth told Psychiatric News. "This offers a
possible explanation for why adolescents and adults who were maltreated as
children have higher rates of behavioral problems, substance abuse, and mental
illnesses. Furthermore, [the results] give us a framework to help explain why
children who have experienced abuse often become abusers
The good news, however, is that it might be possible to interrupt, via
development of a new medication, the molecular transmission of child abuse
from one generation to another, Roth said.
In another experiment, she and her team took six rats that had been
maltreated as pups and infused a DNA methylation inhibitor into their brains
for a week. In a postmorten examination of the rats' brains, the researchers
found that the compound had reversed BDNF gene methylation in their
The study was funded by NARSAD and the Evelyn McKnight Brain Research
An abstract of "Lasting Epigenetic Influence of Early-Life
Adversity on the BDNF Gene" can be accessed at<www.journals.elsevierhealth.com/periodicals/bps>
by clicking on the May 1 issue. ▪