Posts tagged stress
Articles and news from the latest research reports.
Combat Stress in Afghanistan Could Alter Soldiers’ Long-term Neural Makeup
Some soldiers who serve in Afghanistan or other war-torn countries return home with visible injuries: concussions, broken bones or amputated limbs. Many others, though, suffer from injuries we can’t visibly see. The daily strain of being exposed to armed combat, enemy fire and unpredictable explosions can lead to a range of behavioral symptoms, including fatigue, slower reaction times and a difficulty in connecting to one’s immediate surroundings.
A new study of soldiers returning home from Afghanistan, published today online in the Proceedings of the National Academy of Sciences, hints at the underlying cause for these behavioral changes. Researchers from the Netherlands and elsewhere used neurological exams and MRI scanning techniques to examine 33 soldiers before and after a four-month deployment in NATO’s International Security Assistance Force, and compared them to a control group of 26 soldiers who were never deployed.
The results were sobering—and indicate that a relatively short period of combat stress can alter an individual’s neurological circuitry for a long time.
Columbia University Medical Center (CUMC) researchers have identified a potential medical treatment for the cognitive effects of stress-related disorders, including post-traumatic stress disorder (PTSD). The study, conducted in a PTSD mouse model, shows that an experimental drug called S107, one of a new class of small-molecule compounds called Rycals, prevented learning and memory deficits associated with stress-related disorders. The findings were published in the online edition of Cell.
Based on his earlier work in heart and muscle disorders, Dr. Marks reasoned that chronic stress could lead to PTSD by destabilizing type 2 ryanodine receptors (RyR2) in the hippocampus, the brain region that plays a central role in learning and memory. RyR2 are channels that regulate the level of calcium in neurons, which is vital to cell survival and function.
“When we examined the hippocampal neurons of the stressed mice, we found that their RyR2 channels had become destabilized and leaky compared with channels from normal non-stressed mice which were not leaky. There was a remodeling of the channels that we had previously seen in heart and skeletal muscles from animal models of chronic diseases including heart failure and muscular dystrophy. We found these same leaky channels in samples from patients with these disorders but not in those from healthy humans,” said Dr. Marks.
A study in mice conducted by researchers at Tufts University School of Medicine suggests that a woman’s risk of anxiety and dysfunctional social behavior may depend on the experiences of her parents, particularly fathers, when they were young.
The study, published online in Biological Psychiatry, suggests that stress caused by chronic social instability during youth contributes to epigenetic changes in sperm cells that can lead to psychiatric disorders in female offspring across multiple generations.
Acute Stress Alters Control of Gene Activity: Researchers Examine DNA Methylation
ScienceDaily (Aug. 15, 2012) — Acute stress alters the methylation of the DNA and thus the activity of certain genes. This is reported by researchers at the Ruhr-Universität Bochum together with colleagues from Basel, Trier and London for the first time in the journal Translational Psychiatry. “The results provide evidence how stress could be related to a higher risk of mental or physical illness,” says Prof. Dr. Gunther Meinlschmidt from the Clinic of Psychosomatic Medicine and Psychotherapy at the LWL University Hospital of the RUB. The team looked at gene segments which are relevant to biological stress regulation.
In stressful social situations, the methylation patterns (bright spheres) of the DNA change. (Credit: Illustration: Christoph Unternährer and Christian Horisberger)
Epigenetics — the “second code” — regulates gene activity
Our genetic material, the DNA, provides the construction manual for the proteins that our bodies need. Which proteins a cell produces depends on the cell type and the environment. So-termed epigenetic information determines which genes are read, acting quasi as a biological switch. An example of such a switch is provided by methyl (CH3) groups that attach to specific sections of the DNA and can remain there for a long time — even when the cell divides. Previous studies have shown that stressful experiences and psychological trauma in early life are associated with long-term altered DNA methylation. Whether the DNA methylation also changes after acute psychosocial stress, was, however, previously unknown.
Two genes tested
To clarify this issue, the research group examined two genes in particular: the gene for the oxytocin receptor, i.e. the docking site for the neurotransmitter oxytocin, which has become known as the “trust hormone” or “anti-stress hormone”; and the gene for the nerve growth factor Brain-Derived Neurotrophic Factor (BDNF), which is mainly responsible for the development and cross-linking of brain cells. The researchers tested 76 people who had to participate in a fictitious job interview and solve arithmetic problems under observation — a proven means for inducing acute stress in an experiment. For the analysis of the DNA methylation, they took blood samples from the subjects before the test as well as ten and ninety minutes afterwards.
DNA methylation changes under acute psychosocial stress
Stress had no effect on the methylation of the BDNF gene. In a section of the oxytocin receptor gene, however, methylation already increased within the first ten minutes of the stressful situation. This suggests that the cells formed less oxytocin receptors. Ninety minutes after the stress test, the methylation dropped below the original level before the test. This suggests that the receptor production was excessively stimulated.
Possible link between stress and disease
Stress increases the risk of physical or mental illness. The stress-related costs in Germany alone amount to many billions of Euros every year. In recent years, there have been indications that epigenetic processes are involved in the development of various chronic diseases such as cancer or depression. “Epigenetic changes may well be an important link between stress and chronic diseases” says Prof. Meinlschmidt, Head of the Research Department of Psychobiology, Psychosomatics and Psychotherapy at the LWL University Hospital. “We hope to identify more complex epigenetic stress patterns in future and thus to be able to determine the associated risk of disease. This could provide information on new approaches to treatment and prevention.” The work originated within the framework of an interdisciplinary research consortium with the University of Trier, the University of Basel and King’s College London. The German Research Foundation and the Swiss National Science Foundation supported the study.
Source: Science Daily
Learning: Stressed People Use Different Strategies and Brain Regions
ScienceDaily (Aug. 8, 2012) — Stressed and non-stressed people use different brain regions and different strategies when learning. This has been reported by the cognitive psychologists PD Dr. Lars Schwabe and Professor Oliver Wolf from the Ruhr-Universität Bochum in the Journal of Neuroscience. Non-stressed individuals applied a deliberate learning strategy, while stressed subjects relied more on their gut feeling. “These results demonstrate for the first time that stress has an influence on which of the different memory systems the brain turns on,” said Lars Schwabe.
The experiment: Stress due to ice-water
The data from 59 subjects were included in the study. Half of the participants had to immerse one hand into ice-cold water for three minutes under video surveillance. This stressed the subjects, as hormone assays showed. The other participants had to immerse one of their hands just in warm water. Then both the stressed and non-stressed individuals completed the so-called weather prediction task. The subjects looked at playing cards with different symbols and learned to predict which combinations of cards announced rain and which sunshine. Each combination of cards was associated with a certain probability of good or bad weather. People apply differently complex strategies in order to master the task. During the weather prediction task, the researchers recorded the brain activity with MRI.
Two routes to success
Both stressed and non-stressed subjects learned to predict the weather according to the symbols. Non-stressed participants focused on individual symbols and not on combinations of symbols. They consciously pursued a simple strategy. The MRI data showed that they activated a brain region in the medial temporal lobe — the hippocampus, which is important for long-term memory. Stressed subjects, on the other hand, applied a more complex strategy. They made their decisions based on the combination of symbols. They did this, however, subconsciously, i.e. they were not able to formulate their strategy in words. The result of the brain scans was also accordingly: In the case of the stressed volunteers the so-called striatum in the mid-brain was activated — a brain region that is responsible for more unconscious learning. “Stress interferes with conscious, purposeful learning, which is dependent upon the hippocampus,” concluded Lars Schwabe. “So that makes the brain use other resources. In the case of stress, the striatum controls behaviour — which saves the learning achievement.”
Source: Science Daily
Scientists identify new gene linked to PTSD
August 7, 2012
Investigators at Boston University School of Medicine (BUSM) and Veterans Affairs (VA) Boston Healthcare System have identified a new gene linked to post-traumatic stress disorder (PTSD). The findings, published online in Molecular Psychiatry, indicate that a gene known to play a role in protecting brain cells from the damaging effects of stress may also be involved in the development of PTSD.
The article reports the first positive results of a genome-wide association study (GWAS) of PTSD and suggests that variations in the retinoid-related orphan receptor alpha (RORA) gene are linked to the development of PTSD.
Mark W. Miller, PhD, associate professor at BUSM and a clinical research psychologist in the National Center for PTSD at VA Boston Healthcare System was the study’s principal investigator. Mark Logue, PhD, research assistant professor at BUSM and Boston University School of Public Health and Clinton Baldwin, PhD, professor at BUSM, were co-first authors of the paper.
PTSD is a psychiatric disorder defined by serious changes in cognitive, emotional, behavioral and psychological functioning that can occur in response to a psychologically traumatic event. Previous studies have estimated that approximately eight percent of the U.S. population will develop PTSD in their lifetime. That number is significantly greater among combat veterans where as many as one out of five suffer symptoms of the disorder.
Previous GWAS studies have linked the RORA gene to other psychiatric conditions, including attention-deficit hyperactivity disorder, bipolar disorder, autism and depression.
"Like PTSD, all of these conditions have been linked to alterations in brain functioning, so it is particularly interesting that one of the primary functions of RORA is to protect brain cells from the damaging effects of oxidative stress, hypoxia and inflammation," said Miller.
Participants in the study were approximately 500 male and female veterans and their intimate partners, all of whom had experienced trauma and approximately half of whom had PTSD. The majority of the veterans had been exposed to trauma related to their military experience whereas their intimate partners had experienced trauma related to other experiences, such as sexual or physical assault, serious accidents, or the sudden death of a loved one. Each participant was interviewed by a trained clinician, and DNA was extracted from samples of their blood.
The DNA analysis examined approximately 1.5 million genetic markers for signs of association with PTSD and revealed a highly significant association with a variant (rs8042149) in the RORA gene. The researchers then looked for evidence of replication using data from the Detroit Neighborhood Health Study where they also found a significant, though weaker, association between RORA and PTSD.
"These results suggest that individuals with the RORA risk variant are more likely to develop PTSD following trauma exposure and point to a new avenue for research on how the brain responds to trauma," said Miller.
Provided by Boston University Medical Center
Source: medicalxpress.com
Sick from Stress? Blame Your Mom… And Epigenetics
If you’re sick from stress, a new research report appearing in the August 2012 issue of The FASEB Journal suggests that what your mother ate — or didn’t eat — may be part of the cause. The report shows that choline intake that is higher than what is generally recommended during pregnancy may improve how a child responds to stress. These improvements are the result of epigenetic changes that ultimately lead to lower cortisol levels. Epigenetic changes affect how a gene functions, even if the gene itself is not changed. Lowering cortisol is important as high levels of cortisol are linked to a wide range of problems ranging from mental health to metabolic and cardiovascular disorders.
Grin and bear it — smiling facilitates stress recovery
In a study forthcoming in Psychological Science, a journal of the Association for Psychological Science, psychological scientists Tara Kraft and Sarah Pressman of the University of Kansas investigate the potential benefits of smiling by looking at how different types of smiling, and the awareness of smiling, affects individuals’ ability to recover from episodes of stress.
"Age old adages, such as ‘grin and bear it’ have suggested smiling to be not only an important nonverbal indicator of happiness but also wishfully promotes smiling as a panacea for life’s stressful events," says Kraft. "We wanted to examine whether these adages had scientific merit; whether smiling could have real health-relevant benefits."
Stress May Cause Women’s Brains to Age Earlier
By Makini Brice | July 26, 2012
Scientists were surprised, expecting the areas of the brain to age more slowly, or even delayed, than those of men.
Photo: Microsoft
Even though the gap is closing now in many high-income countries, on average, women tend to live longer lives than men do. Despite – or perhaps because of – women’s physical longevity, women tend to battle cognitive decline in much greater numbers than men do. In fact, women are more likely to suffer from various types of dementia, including the much-maligned Alzheimer’s disease. Now researchers think that they have an answer to the cause of this double-edged sword: stress. Specifically, stress ages women’s brains more quickly than it does men.
Scientists, and every-day observers, have noted that some body parts age at different rates than others do. As people become older, some genes become more active while others become less so. These changes in activity can be monitored through a “transcriptome,” which collects data on all the RNA – the transcripts that carry DNA’s instructions to cells. A multinational team from Australia, China, Germany, and the United States set out to analyze the transcriptomes for 55 different men and women of various ages.
The researchers were fascinated by what they found. According to the abstract of their article published in Aging Cell, “In the superior frontal gyrus (SFG), a part of the prefrontal cortex, we observed manifest differences between the two sexes in the timing of age-related changes, i.e.sexual heterochrony. Intriguingly, age-related expression changes predominantly occurred earlier, or at a faster pace, in females compared to males. These changes included decreased energy production and neural function, and up-regulation of the immune response, all major features of brain aging.”
In other words, researchers found that the brains of women aged more quickly than those of men, especially in the prefrontal cortex. Scientists were surprised, expecting the areas of the brain to age more slowly, or even delayed, than those of men.
In the superior frontal gyrus, researchers found 667 genes that were expressed differently by gender during the aging process. Within that number, 98 percent were associated with faster aging in women.
Scientists were not convinced that the reason lay in biological differences. In fact, since only half of women displayed accelerated aging, they were convinced that the difference was environmental. Researchers theorize that stress is the difference-maker, and that it affects women’s brains more severely than it does men. While a researcher unaffiliated with the study said that the difference could also be caused by inflammation,
Mehmet Somel and his team have conducted similar research on monkeys that confirms their stress theory.
Source: Medical Daily
Force of habit: Stress hormones switch off areas of the brain for goal-directed behaviour
July 25, 2012
Cognition psychologists at the Ruhr-Universität together with colleagues from the University Hospital Bergmannsheil (Prof. Dr. Martin Tegenthoff) have discovered why stressed persons are more likely to lapse back into habits than to behave goal-directed. The team of PD Dr. Lars Schwabe and Prof. Dr. Oliver Wolf from the Institute for Cognitive Neuroscience have mimicked a stress situation in the body using drugs. They then examined the brain activity using functional MRI scanning. The researchers have now reported in the Journal of Neuroscience that the interaction of the stress hormones hydrocortisone and noradrenaline shut down the activity of brain regions for goal-directed behaviour. The brain regions responsible for habitual behaviour remained unaffected.
In order to test the different stress hormones, the cognition psychologists used three substances - a placebo, the stress hormone hydrocortisone and yohimbine, which ensures that the stress hormone noradrenaline stays active longer. Part of the volunteers received hydrocortisone alone or just yohimbine, others both substances. A fourth group were administered a placebo. Altogether, the data of 69 volunteers was included in the study.
In the experiment, all participants - both male and female - learned that they would receive cocoa or orange juice as a reward if they chose certain symbols on the computer. After this learning phase, volunteers were allowed to eat as many oranges or as much chocolate pudding as they liked. “That weakens the value of the reward”, explained Schwabe. “Whoever eats chocolate pudding will lose the attraction to cocoa. Whoever is satiated with oranges, has less appetite for orange juice.” In this context, goal-directed behaviour means: Whoever has previously eaten the chocolate pudding, chooses the symbols leading to cocoa reward less frequently. Whoever is satiated with oranges, selects less frequently the symbols associated with orange juice. Based on previous results, the scientists assumed that only the combination of yohimbine and hydrocortisone attenuates goal-directed behaviour. They have now confirmed this hypothesis.
As expected, volunteers who took yohimbine and hydrocortisone did not behave goal-directed but according to habit. In other words, satiation with oranges or chocolate pudding had no effect. Persons who had taken a placebo or only one medication, on the other hand, behaved goal-directed and showed a satiating effect. The brain data revealed: The combination of yohimbine and hydrocortisone reduced the activity in the forebrain – in the so-called orbitofrontal and medial prefrontal cortex. These areas have been already previously associated with goal-directed behaviour. The brain regions which are important for habitual learning, on the other hand, were similarly active for all volunteers.
Provided by Ruhr-Universitaet-Bochum
Source: medicalxpress.com