Nature and nurture play role in mental illness

Nature and nurture play role in mental illness

By Julie Steenhuysen and Ben Hirschler / Reuters
Mon Feb 4, 2008 4:27 PM ET

Variations in a gene helped
shield adults who had endured child abuse from becoming
depressed as adults, U.S. researchers said on Monday in a study
that helps explain how nature and nurture give rise to mental
illness.

And a British team has found that pregnant women who have a
major emotional loss in the early months of pregnancy give
birth to babies with a higher risk of schizophrenia.

The studies, published in the Archives of General
Psychiatry, add to a growing understanding of how genetics and
environmental distress sometimes act together to produce mental
illness.

"It is not a question of genes versus environment. It is a
question of how genes interact with whatever the environmental
factors might be. And that is probably true of all of the
disorders that we call mental illness," said Dr. Thomas Insel,
director of the National Institutes of Mental Health.

"There is going to be a genetic factor that gives you the
risk. And it all depends on what happens in a person’s
lifetime," Insel said in a telephone interview.

In the depression study, Dr. Kerry Ressler of Emory
University in Atlanta found that some variations in a gene that
regulates the stress hormone corticotropin-releasing hormone,
or CRH, could protect those who had been abused as children.

Ressler and colleagues took DNA samples from 422 adults,
most of whom were poor and black, and found about a third of
them had the genetic variations.

People in this group who also had a history of abuse had
half the symptoms of moderate to severe depression as those who
did not have the protective variations of this gene. The
researchers repeated the study in 199 wealthier white adults
and came up with similar results.

The study builds on other research linking genes and
stressful events with depression. A 2003 study in New Zealand
found that people with a short version of a gene that relays
the chemical messenger serotonin were more prone to depression
after losing a job or a loved one.

NURTURE AND NATURE

"What we think these days is there isn’t such a divide
between nature and nurture," Dr. Kathryn Abel of the Centre for
Women’s Mental Health Research at Britain’s University of
Manchester said in a telephone interview.

Abel’s schizophrenia study looked at 1.38 million babies
born in Denmark between 1973 and 1995. Her team found the risk
of schizophrenia was two-thirds greater among offspring whose
mothers experienced the death of a relative during the first
trimester.

The link disappeared after the first three months, however,
perhaps because barriers are built up between mother and fetus
later on that protect the unborn baby from stress hormones
released by the mother.

Abel said it was possible the mother’s hormones may either
have a direct impact on development of the fetus brain or
affect it indirectly by altering the activity of certain genes.

Schizophrenia is known to run in some families, indicating
a genetic component to the disease, yet 90 percent of cases are
still classed as nonfamilial or sporadic.

The new study found the association between a family death
and the risk of schizophrenia was only significant in this
sporadic setting, where a child’s parents, grandparents or
siblings had no history of mental illness.

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