2008 July 06 Sunday
More Anxious Monkeys Have More Amygdala Activity

Rhesus monkeys that are more prone to anxiety have more activity in the amygdala part of the brain even when in a secure situation.

We all know people who are tense and nervous and can't relax. They may have been wired differently since childhood.

So if you are like the character "Tweak" in South Park you probably didn't get that way by drinking coffee. You just feel more stress and feel more nervous all the time. Blame it on your amygdala.

New research done by the HealthEmotions Research Institute and Department of Psychiatry at the School of Medicine and Public Health (SMPH) indicates that the brains of those suffering from anxiety and severe shyness in social situations consistently respond more strongly to stress and show signs of being anxious even in situations that others find safe.

Ned Kalin, chair of the UW-Madison Department of Psychiatry and director of the HealthEmotions Research Institute, in collaboration with graduate student Andrew Fox and others, has published a new study on anxious brains on the Public Library of Science (PLoS One) Web site today (July 2).

The study looked at brain activity, anxious behavior and stress hormones in adolescent rhesus monkeys, which have long been used as a model to understand anxious temperament in human children. Anxious temperament is important because it is an early predictor of the later risk to develop anxiety, depression and drug abuse related to self-medicating. The researchers found that those individuals with the most anxious temperaments showed higher activity in the amygdala, a part of the brain that regulates emotion and triggers reactions to anxiety, such as the fight or flight response. These anxious monkeys had more metabolic activity in the amygdala in both secure and threatening situations.

Suppose kids with anxious temperaments can be identified when they are 5 years old. Should anti-anxiety drugs be developed that are safe for long term use by children? Look at Ritalin use for hyperactive kids. Hyperactivity was probably adaptive in our nomadic past and therefore genes that cause it were selected for. Similarly, greater tendency to anxiety might have had adaptive value even as recently as a hundred years ago. But now in a modern context a greater tendency toward anxiety is maladaptive. Should children be given drugs that adapt them to modern industrial society?

By Randall Parker    2008 July 06 08:59 PM   Entry Permalink | Comments (4)
2008 March 18 Tuesday
Combat Stress Shrinks Brain Area

Combat veterans from the Vietnam era have less gray matter in their pregenual anterior cingulate cortex as compared to their twins who did not serve.

Philadelphia, PA, March 18, 2008 – Individuals who experience military combat obviously endure extreme stress, and this exposure leaves many diagnosed with the psychiatric condition of post-traumatic stress disorder, or PTSD. PTSD is associated with several abnormalities in brain structure and function. However, as researcher Roger Pitman explains, “Although it is tempting to conclude that these abnormalities were caused by the traumatic event, it is also possible that they were pre-existing risk factors that increased the risk of developing PTSD upon the traumatic event’s occurrence.” Drs. Kasai and Yamasue along with their colleagues sought to examine this association in a new study published in the March 15th issue of Biological Psychiatry.

The authors measured the gray matter density of the brains of combat-exposed Vietnam veterans, some with and some without PTSD, and their combat-unexposed identical twins using a technology called magnetic resonance imaging (MRI). The detailed images provided by the MRI scans then allowed the investigators to compare specific brain regions of the siblings. They found that the gray matter density of the pregenual anterior cingulate cortex, an area of the brain involved in emotional functioning, was reduced in veterans with PTSD, but not in their twins who had not experienced combat. According to Dr. Pitman, “this finding supports the conclusion that the psychological stress resulting from the traumatic stressor may damage this brain region, with deleterious emotional consequences.”

A history of childhood abuse increases the risk that adult stress will cause post traumatic stress disorder and some variants of the gene FKBP5 increase that risk even further.

A traumatic event is much more likely to result in posttraumatic stress disorder (PTSD) in adults who experienced trauma in childhood – but certain gene variations raise the risk considerably if the childhood trauma involved physical or sexual abuse, scientists have found. The research was conducted with funding from the National Institute of Mental Health, which is part of the National Institutes of Health, and others.


Inherited variations in multiple genes, which have yet to be identified, are estimated to account for 30 to 40 percent of the risk of developing PTSD. The gene identified in this study is one likely candidate, although others are almost certain to emerge.

To conduct their study, the researchers surveyed 900 primarily African-American people 18 to 81 years old, from poor, urban neighborhoods. As is common in impoverished environments, many of the people in this study had experienced severe traumatic experiences in childhood and had later experienced other kinds of trauma as adults. The researchers also examined the genetic make-up of 765 of the participants.

They found that having a history of child abuse – which was the case for almost 30 percent of the people in this study – led to more than twice the number of PTSD symptoms in adults who had later undergone other traumas, compared to traumatized adults who weren’t abused in childhood. But the history of child abuse wasn’t enough, by itself, to lead to the increase in symptoms; the increase appeared to depend on whether or not certain variations in the stress-related gene also were present.

At some point in the future I picture potential soldiers undergoing genetic screening. Then if you are unlucky enough to have a genetic profile that makes you more immune to PTSD you'll get assigned to more dangerous front line combat units.

But then brain gene therapy to make soldiers more immune to stress will take even abused kids with bad genetic profiles and turn them into relaxed combat leaders who can handle extended periods of combat with little long term brain damage.

By Randall Parker    2008 March 18 10:53 PM   Entry Permalink | Comments (9)
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