Brain structures implicated in PTSD
The amygdala is comprised of a pair of almond-shaped structures—the amygdalae—located on each side of the brain (see figure 2.1). The amygdala plays a key role in the regulation of traumatic memories and of general emotional processing. It’s involved in fear conditioning, a term that refers to the process by which fear is triggered by events around us. Post-traumatic changes in the amygdala may account for the hypervigilance associated with PTSD.2
The amygdala is overactive in people with PTSD. The left and right amygdalae have slightly different functions: the left amygdala is involved in a more detailed processing of emotion that involves thinking; the right processes emotion in a more automatic way.3 The right amygdala shows increased activation in PTSD.4
Meditation reduces overactivation of the amygdala. Chanting Om has been shown to decrease activation of the right amygdala.5 Participants in an eight-week mindfulness-meditation program had significant deactivation of the right amygdala when they were shown emotionally charged images.6 These meditation studies on the amygdala were done in healthy volunteers.
Such studies have not been done with PTSD patients but have been done using CBT [cognitive behavioural therapy] protocols. Results showed CBT treatment also resulted in reductions in amygdala activity.7
The word “hippocampus” comes from the Greek word for seahorse, due to this brain structure’s resemblance to that creature. We have two hippocampi, one on each side of the brain (see figure 2.1).
The hippocampus stores new memories, processes long-term memory and appears to interact with the amygdala during the encoding of emotional memories. Because studies of laboratory animals under extreme stress show both damage to the hippocampus and memory impairment, hippocampus damage is believed to play a role in PTSD memory disturbances.8
A smaller hippocampus may make one vulnerable to developing PTSD, rather than PTSD causing the hippocampus to shrink.
The hippocampus is reduced in size in those with PTSD. Several studies have found that a smaller hippocampus correlates with more severe PTSD symptoms. In order to determine whether PTSD causes the hippocampus to shrink or if in fact people with a smaller hippocampus are more prone to develop PTSD, a study was done in 40 pairs of male twins; in each pair, one was a Vietnam combat veteran and the other had no combat exposure. The results of this study suggest that a smaller hippocampus may make one vulnerable to developing PTSD, rather than PTSD causing the hippocampus to shrink.9
However, if a smaller hippocampus was a risk factor for PTSD we would expect people with either current or past PTSD to have a smaller hippocampus. This was not the case in a study of Gulf War veterans; those who recovered from PTSD actually had a larger hippocampus.10 This may be due to the ability of the hippocampus to generate new nerve cells and increase in size.
Yoga, meditation and CBT all increase hippocampal volume, often rather quickly. Studies of mindfulness meditation showed significant hippocampus increases after just eight weeks.11 Yoga has also been shown to increase the size of the hippocampus in older people after six months of Yoga practice.12 Twelve weeks of CBT have been found to increase the size of the hippocampus and improve memory in people with PTSD.13
Anterior cingulate cortex
The anterior cingulate cortex (ACC) is located in the front part of the cingulate cortex, which enwraps the corpus callosum that connects the two sides of the brain. The ACC regulates emotion and the stress response. It’s involved in behavioral inhibition and fear conditioning.14 Trauma may degrade the ACC’s ability to regulate the amygdala, resulting in an enhanced fear response to PTSD triggers.15
The ACC is altered in both size and activity in PTSD. Vietnam veterans with PTSD were found to have decreased ACC activity compared to veterans without PTSD.16 The ACC is also physically smaller in the brains of people who have been exposed to trauma as compared to those not so exposed.17 The results from the Vietnam veteran twins study showed that reduced size of the ACC is most likely due to trauma, as opposed to being a predisposing factor in developing PTSD.18
Both CBT and meditation can reverse changes to the ACC found in PTSD. ACC thickness was increased in Zen meditators and the increase in thickness correlated to years of practice: those with more meditation experience had a thicker ACC.19 Mindfulness meditation also resulted in increased activation of the ACC in experienced meditators.20 Increased ACC activation was found following CBT treatment as well, and correlated with a decrease in PTSD symptoms.21
Table 2.1. Effect of Trauma on the Brain and
the Healing Role of Yoga, Meditation and CBT
|Region of Brain||Functions||Effect of Trauma||Effect of Yoga, Meditation and CBT|
|Amygdala||Overactivation||Meditation and CBT decrease activity|
|Hippocampus||Decreased size||Yoga, meditation and CBT increase size|
|Anterior cingulate cortex||Decreased size and activity||Meditation increases size and activity; CBT increases activity|
Physiologic effects of PTSD
PTSD changes not only the body’s structure but its function as well. Trauma affects activity in many systems in the body including the nervous, endocrine and immune systems.
Gamma-aminobutyric acid (GABA) is the main inhibitory neurotransmitter in the brain and is found in the blood as well. GABA reduces electrical signals in nerve cells, which has a calming effect on the whole person.
Yoga has also been found to increase GABA levels in the brain, and this can happen very quickly. In one study, one hour of Yoga practice increased practitioners’ brain GABA levels 27 percent. Comparison subjects who read a book for one hour had no change in GABA levels.23 Another study found increases in GABA after 12 weeks of Yoga practice that correlated with improved mood and decreased anxiety.24
The nervous system and heart rate variability
The sympathetic nervous system is associated with arousal and the parasympathetic nervous system with relaxation (see figure 2.2).
One measure of the balance between these sides of the nervous system is heart rate variability. Heart rate variability is the variation in the time interval between heartbeats. High heart rate variability is healthy and suggests that the parasympathetic nervous system is dominating. Low heart rate variability is unhealthy and indicates that the sympathetic nervous system is dominating.
Given the high state of arousal in PTSD it’s not surprising to find it associated with low heart rate variability.25 Low heart rate variability may also be a predisposing factor to developing PTSD.26 Yoga has been shown to increase heart rate variability.27 Studies also show CBT produces heart rate variability changes in women with PTSD.28
Our bodies are hardwired to respond to emergencies. The human stress response releases the hormones adrenaline and cortisol to shut down physical systems not needed in an emergency. When the emergency has passed, our bodies are designed to reset to baseline. This system works very well in the short-term and can indeed save our lives. But repeated attempts to adapt to chronic stressors have a cumulative negative effect on our bodies known as “allostatic load.”29
Allostatic load is measured by such biological markers as blood pressure, cholesterol, stress hormones and blood sugar levels. Mothers with PTSD whose children had been diagnosed with cancer had trauma symptoms directly related to allostatic load; those with the highest levels of PTSD symptoms also had the highest allostatic loads.30
Insomnia, a common PTSD symptom, is another stressor that contributes to allostatic load. Four months of CBT produced decreased disease biomarkers in insomnia patients.31 Studies have not yet measured the effect of Yoga on allostatic load, but we know that Yoga improves factors associated with allostatic load.
As noted above Yoga increases GABA and increases parasympathetic dominance as measured by increased heart rate variability. Yoga also decreases stress hormone production.32 When PTSD increases allostatic load, CBT and Yoga reduce and repair the wear and tear on the body, returning us to a balanced state.
CBT has been shown to regulate the stress response even at the level of gene expression. FKBP5 is a gene that plays a role in modulating the stress response. Although the expression of this gene is reduced when there is PTSD, 12 weeks of CBT was found to increase the expression of FKBP5 in study participants with PTSD.33
Inflammation is a protective response to tissue injury, microbial infection and irritants, but when inflammation is out of control it can cause damage to healthy tissue.
Yoga practice returns the body to a healthy cytokine balance by decreasing pro-inflammatory cytokines and increasing anti-inflammatory cytokines.
Inflammation is associated with many diseases including heart disease, diabetes, arthritis, osteoporosis, Alzheimer’s and cancer. It’s regulated by proteins called cytokines, which can be either pro-inflammatory or anti-inflammatory. Levels of these cytokines in the blood indicate the degree of inflammation in the body. PTSD is associated with a pro-inflammatory state as a result of an increase in pro-inflammatory cytokines and a decrease in anti-inflammatory cytokines.34
Yoga practice returns the body to a healthy cytokine balance by decreasing pro-inflammatory cytokines and increasing anti-inflammatory cytokines.35* CBT has also been shown to decrease pro-inflammatory cytokines in the blood after only seven weeks of treatment.36 Just as CBT has been shown to regulate genes associated with the stress response, both Yoga and CBT regulate inflammatory genes.
Reduced inflammation-related gene expression was found in people practicing a meditation from Kundalini Yoga as taught by Yogi Bhajan.®37 Comparable results were seen in women with breast cancer who participated in a different Yoga program.38 Women with breast cancer who received CBT after surgery also had a significant down-regulation of the genes that code for pro-inflammatory cytokines.39
Telomeres are protective DNA sequences at the tips of chromosomes that serve to stabilize them. As we age, telomeres shorten. Shortened telomeres are associated with several diseases including diabetes, heart disease and cancer. Telomere shortening may result from increased sympathetic nervous system activity, inflammation, oxidation and certain stress hormones.
Emerging evidence suggests that telomeres are also shortened in those with PTSD.40 Yoga may help preserve telomere length. There is a strong genetic variant involved in telomere maintenance, but longer telomeres have also been found in Yoga practitioners with at least two years of practice compared to a sedentary group.41
Table 2.2. Effect of Trauma on the Autonomic Nervous System, the Endocrine System, and the Immune System and the Healing Role of Yoga, Meditation and CBT
|System||Healthy Status||Effect of Trauma||Effect of Yoga, Meditation and CBT|
|Autonomic Nervous System: Heart Rate Variability||High heart rate variability (parasympathetic dominance)||Low heart rate variability (sympathetic dominance)||Yoga and CBT increase heart rate variability|
|Endocrine System and Autonomic Nervous System: Stress Response and Allostatic Load||Low stress levels/low allostatic load||Increased stress levels/high allostatic load||Yoga improves factors involved in allostatic load; CBT reduces allostatic load|
|Immune System: Inflammation||Balance of pro-inflammatory cytokines||Increased pro-inflammatory cytokines and decreased anti-inflammatory cytokines||Yoga and CBT decrease pro-inflammatory cytokines and increase anti-inflammatory cytokines|
|Endocrine System, Autonomic Nervous System and Immune System: Telomere Length||Healthy telomere length||Shortened telomeres||Yoga supports healthy telomere length|
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