Researchers identify areas key to anxiety disorder; Temperament could be

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Today, I am pleased to share an article with you that was submitted by Erin Cofax.  An article that discusses the link between anxiety disorders and genetics.  I hope you find it of great interest and I thank Erin for her submission.
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Researchers identify areas key to anxiety disorder; Temperament could be
result of inherited genetic condition, Nature reports

 

Sarah Perdue
The Toronto Star , Aug. 17, 2010

 

When a child encounters strangers, it is normal for him to freeze and be
quiet for a few moments. When that child's reaction lasts too long or he is
too apprehensive, he may have a disorder known as anxious temperament, a
risk factor for depression or other anxiety disorders that develop later in
life.

 

Psychiatrists are able to identify the disorder, but treatments are
difficult to develop because the cause of anxious temperament is unknown.

 

In the largest non-human primate neuroimaging study to date, University of
Wisconsin-Madison researchers have identified brain regions that are
overactive in the most anxious monkeys, and they were able to show that the
response in one of those regions is likely an inherited genetic condition.
The researchers hope to use their data to find the genes that predispose
people to the disorder and provide a target for drug therapy, and it may
help to identify children who are at-risk based on a family history of
depression and anxiety.

 

The study appears in the current issue of the journal Nature.

 

The impacts of the study are twofold, according to Andrew Fox, a graduate
student in psychology at the University of Wisconsin-Madison and co-lead
author of the study.

 

He said the size of the study - 238 young monkeys - gave researchers
statistical significance that the two brain regions identified were likely
to be the most important and confirmed the validity of an animal model for
studying this mood disorder.

 

More importantly, Fox said, "because we have shown this in such a large
sample of animals, and because they were from a single family, we were able
to look at heritability within a single family tree."

 

By identifying which brain regions have an inherited component that
contributes to disease development, the researchers can start to look for
genes that are active specifically in that region.

 

"The idea is that we have tons of different genes expressed in our bodies,
and if we look at everything going on everywhere we don't know where to
start," Fox said.

 

To figure out where to start, the researchers injected monkeys with a mostly
harmless radioactive variant of the sugar glucose (it is used in humans to
diagnose Parkinson's, for example), then immediately challenged the animals
in an "intruder" test designed to mimic a stranger approaching a child in a
non-threatening way. They assessed how the animals responded, and assigned
them to a relative scale of anxious temperament based on how long the animal
froze, how quiet it was, and how high its stress hormone levels were.

 

Next, they anesthetized the monkeys and imaged their brains, using the
radioactive sugar to indicate which brain regions were the most active - and
thus needed the most energy. They found that the more anxious behaviour the
monkey displayed, the more active its amygdala and hippocampus were.

 

"If you ask most neuroscientists what area of the brain would be critical in
anxious temperament and emotion, most would say the amygdala," said Jonathan
Oler, an associate scientist at the Health Emotions Research Institute at
the University of Wisconsin-Madison and co-lead author of the study.

 

The amygdala is known to have a strong correlation with anxiety and stress
responses. The hippocampus, however, was previously thought to be mostly
involved with memory.

 

"But the data are the data, and the hippocampus and the amygdala predicted
anxiety in the monkey equally," Oler said. "What was different between them
was the heritability component."

 

"The exciting part was that the hippocampus was the region that was most
affected by genes," said Ned Kalin, chairman of psychiatry at the University
of Wisconsin School of Medicine and Public Health and senior author of the
study.

 

"Now we can go and ask which genes that have to do with hippocampal function
are inherited," Kalin said. "The amygdala, which has been the focus of
attention for lots of reasons, is less heritable than the hippocampus."

 

"Mental health researchers currently are struggling to develop more
effective treatments for a range of mental disorders, including mood and
anxiety disorders," said Daniel S. Pine, chief of the section on development
and affective neuroscience at the National Institute of Mental Health, who
was not involved in the study.

 

"This work is one vital step toward developing coherent understanding of
neural processes that cause mood and anxiety disorders."

 

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