• Quote of the Day
    "Too bad the only people who know how to run the country are busy driving cabs and cutting hair."
    George Burns, posted by David Baxter

David Baxter

Administrator
Joined
Mar 26, 2004
Messages
37,774
Points
113
Gene variants linked to social anxiety disorder
March 5, 2009

Massachusetts General Hospital (MGH) researchers - in collaboration with University of California at San Diego and Yale University scientists - have discovered perhaps the strongest evidence yet linking variation in a particular gene with anxiety-related traits.

In the March issue of Archives of General Psychiatry, the team reports finding that particular versions of a gene that affects the activity of important neurotransmitter receptors were more common in both children and adults assessed as being inhibited or introverted and also were associated with increased activity of brain regions involved in emotional processing.

"We found that variations in this gene were associated with shy, inhibited behavior in children, introverted personality in adults and the reactivity of brain regions involved in processing fear and anxiety," says Jordan Smoller, MD, ScD, an associate professor of Psychiatry at Harvard Medical School, the report's lead author. "Each of these traits appears to be a risk factor for social anxiety disorder, the most common type of anxiety disorder in the U.S."

It has long been recognized that the tendency to anxiety disorders can run in families and is believed to be influenced by the interaction of several genes. Because of the different forms of these disorders and their complex patterns of inheritance, identifying specific susceptibility genes has been difficult. Studies in mice have associated an area of chromosome 1 with anxious temperament, particularly the gene that codes for a protein called RGS2, which mediates the activity of neurotransmitter receptors that are also the targets of many antidepressant and antipsychotic drugs. Mice in whom RGS2 is deactivated exhibit increased fearful behavior.

To more comprehensively investigate the role of RGS2 in humans, the researchers conducted several experiments. They analyzed blood samples from children from 119 families who had participated in an earlier study assessing their reactions to unfamiliar situations at the ages of 21 months, 4 and 6 years. The participants had been evaluated on their levels of behavioral inhibition, a form of temperament linked to increased risk of anxiety disorders. Testing several sites in the RGS2 gene identified nine variations that appeared to be associated with inhibition.

The second experiment involved more than 700 college students who had completed questionnaires designed to measure several personality traits. Analyzing blood samples from this group, the research team genotyped the four gene markers that had demonstrated the strongest effects in the first group. They found that the versions associated with inhibited behavior in the children were also more common in the college students who scored high on measures of introversion, a personality trait that also involves social inhibition.

Another group of 55 college students had functional MRI brain imaging done after they had completed a standard interview screening for anxiety and mood disorders. While in the MRI scanner, the participants viewed a series of faces expressing various emotions, a test that previously was shown to influence activity in the amygdala, a brain structure involved in emotion processing. Participants with the inhibition/introversion-associated alleles also had increased activity of the amygdala and the insula, another anxiety-related brain region.

"Now we need to investigate whether these RGS2 variants actually are associated with particular disorders and how they act on a cellular level," says Smoller. "We hope that ultimately this work will lead to new drug targets and treatment options for anxiety disorders."

Source: Smoller JW, Paulus MP, Fagerness JA, et al. Influence of RGS2 on Anxiety-Related Temperament, Personality, and Brain Function. Arch Gen Psychiatry. 2008;65(3):298-308.
 

xenopath

Member
Joined
Mar 26, 2007
Messages
36
Points
6
Interesting. I understand how cowardice and aversion to new experiences could be evolutionarily adaptive, but I don't see the survival benefit from shyness. How has this gene survived?
 

David Baxter

Administrator
Joined
Mar 26, 2004
Messages
37,774
Points
113
I'm no expert in evolution but what comes to mind is this:

1. Shy introverted people tend to be more reflective and less impulsive, all other things being equal. For a community/species to survive, it needs a certain number of extraverted, impulsive people who are comfortable with trial and error and will charge into battle to protect the community (e.g., policemen or soldiers). But it also needs a certain number of introverted, reflective people who will hold back and consider other alternatives both personally and for the community as a whole.

2. Additionally, not all traits (physical or psychological) are necessarily adaptive for the individual but introduce genetic variability into the gene pool to promote adaptation and further evolution as socio-environmental conditions change over time.

3. Some traits attached to certain genes may be secondary to that gene, with the other traits having direct survival value and one or two being neutral in that respect (e.g., handedness, perhaps?).
 

xenopath

Member
Joined
Mar 26, 2007
Messages
36
Points
6
I can see that introversion is a useful trait for a society to have in small doses, but shyness seems more like a hinderance with no upside. Do you think it is just an unfortunate side-effect of the mutation leading to introverted behaviour?
 

David Baxter

Administrator
Joined
Mar 26, 2004
Messages
37,774
Points
113
The upside to shyness may be similar to the common phenomenon of neophobia in children: Beware of and show caution around new things, whether they are food, animals, or other people, until you have proof they are safe.
 

Top Bottom