Hans Selye, a Canadian endocrinologist of Austro-Hungarian origin, was the first to apply the word "stress" to physical and emotional strain. Before that, "stress" was just an engineering term. Selye, who did the bulk of his research in the 1930s, discovered that the stress hormone cortisol had detrimental health effects in rats. (ref 1) Together with other adrenal gland hormones, cortisol prepares the body for a "fight or flight" response. The limbic brain's fear center known as the amygdala, modulates the release of cortisol and other stress hormones. But researchers have now discovered that elevations of cortisol can also lead to structural alterations in the amygdala.
The Vicious Cicle
According to the Association for Psychological Science, when you believe you are threatened, a defense mechanism kicks in. Amygdala activation increases the release of adrenal hormones, such as epinephrine, also known as adrenaline, norepinephrine and cortisol. These hormones increase heart rate, respiration and glucose levels. The result is a "fight or flight" reaction. Normally, stress hormones return to a normal level when the threat is eliminated. But when people suffer from psychological stress over prolonged periods of time, the hormones stay at an elevated level. This can affect body tissues ranging from the dental lines to the heart and can cause dysfunction of the amygdala.
Studies in Mice
Scientists have known for some time that stress is linked to anxiety and depression but the evidence was circumstantial. Now Harvard researchers have discovered a direct link between long-term exposure to cortisol and semi-permanent alterations in the amygdala. They injected two groups of mice with cortisol. One group was exposed for just one day, whereas the other group was exposed to the stress treatment for two weeks. The second group of mice developed semi-permanent fear symptoms. They were unwilling to explore new environments and demonstrated dulled reactions to startling stimuli, say Paul Ardayfio and Kwang-Soo Kim, the study's authors.
Depression
People with depression have abnormal activity in the ventromedial prefrontal cortex, or VMPFC, involved in regulating the fear output from the amygdala. Neuroscientist Antonio Damasio and his team at University of Southern California have shown that when this area is compromised, people are unable to make rational long-term decisions and moral judgments. Researchers from the University of Wisconsin and Tufts University have now discovered that VMPFC dysfunction in depression can impair people's ability to suppress negative emotional states when exposed to fearful events. This inability to suppress fear impairs the normal regulation of cortisol levels, which in turn can contribute to a continued elevation of abnormal amygdala output, write the scientists.
Post-Traumatic Stress Disorder
When you are exposed to a very traumatic event, such as war, torture, disasters, domestic violence, sexual assault, emotional abuse or extreme shock, your body reacts by sending a surge of stress hormones, including cortisol, though your body. Researchers have known for some time that individuals who have a shorter version of the serotonin transporter gene are at a higher risk for developing depression and post-traumatic stress disorder after extremely stressful events. Neuroscientist Richard Bryant from University of New South Wales and his team have now discovered that this same gene variant also affects activation in the amygdala and hence the time it takes to recover from post-traumatic stress disorder.
Possible Treatment
People with the defective variant of the serotonin transporter gene don't always respond well to standard treatments of anxiety, depression and stress disorders. They may not show any response to serotonin reuptake inhibitors or pscyhotherapy. Now researchers from Norway have found that a pharmacological version of the street drug ecstasy, used illegally at dance clubs to create an artificial feeling of emotional closeness, can make patients with post-traumatic stress disorder more receptive to psychotherapy. Ecstasy increases the level of the trust hormone oxytocin in the brain and activates the VMPFC areas usually compromised in these patients, the scientists say.
References
- Science Daily: Understanding Role Of Stress In Just About Everything
- Chronic Exposure To Stress Hormone Causes Anxious Behavior In Mice
- Science Daily: Depression: Brain Imaging Reveals Breakdown Of Normal Emotional Processing
- Science Daily: Post-Traumatic Stress Disorder
- Science Daily: Ecstasy For Treatment Of Traumatic Anxiety
