A mental illness caused by trauma may be one of the first to be understood in physical terms
PTSD, originally recognized during and after WWII as 'battle fatigue" It labels a constellation of signs and symptoms which have been studied with modern neuroscience.
Accounts of debilitating fear after trauma date back to the Trojan wars. In the 19th century survivors of train crashes were diagnosed with “railway spine” because doctors thought their hysteria was caused by compression of the backbone. In the first world war it was known as shell shock, soldier’s heart or battle fatigue. Not until soldiers returned from the Vietnam war with the same symptoms of hyper-vigilance, flashbacks and nightmares was the disorder truly taken seriously. In 1980 an umbrella term was coined: post-traumatic stress disorder (PTSD).
Attitudes are now quite different from those that prevailed during the second world war, when George Patton, an American general, threatened to court-martial men with battle fatigue. And research is progressing swiftly. A remarkable amount has been discovered about the causes of PTSD and how to treat it—which is welcome, because another discovery is how common it is.
According to Charles Marmar, a psychiatrist at New York University’s medical centre, it may be the first psychiatric disorder “where we crack the mind-brain connections”.
Neural research is helping to reveal how people get stuck in a state of fear. The amygdalae, a pair of almond-sized regions deep in the brain, are the main orchestrators of fear, reading incoming signals such as smells and sounds and sending messages to other bits of the brain, which filter the signals before reacting. In someone with PTSD the filters struggle to distinguish between real threats and those that can safely be ignored.
The brain of a healthy person given cause to panic will tell the body to activate various reactions, including releasing adrenalin. A person’s heart rate will increase and they will have a strong urge to fight or flee. Once back to safety, symptoms subside and all that remains is a bad memory. A woman assaulted in a noisy bar may react fearfully to the sound of clinking glasses for a few weeks, but over time, in what is called “fear extinction”, the positive association of celebrating with friends will outweigh negative ones. The more often people receive such reminders without suffering a disaster, the more likely the fear is to dissipate—which is why it is important not to hide away after a trauma.
Retraining the brain
When this mechanism fails, the result is PTSD. A soldier returning from war may continue to freeze and have debilitating flashbacks when anything reminds him of combat. One ex-soldier tells of “freaking out” every time his wife baked: it turned out that the smell of almonds evoked Semtex, an explosive. People who were abused as children may suffer when it is dark, because such abuse often happens at night.
Studies of twins suggest that susceptibility to PTSD is about 30% genetic. Researchers in the new field of epigenetics—the study of how external factors influence the way the instructions written in genes are expressed in organisms—have produced some evidence to suggest that stress might be passed on to offspring.
An exciting recent development is the discovery of markers that show differences between the brains, genes and even blood of people with and without PTSD. When a sufferer sees a picture of a frightened face, the amygdala shows a heightened response. At the same time the prefrontal cortex, which regulates fear, is suppressed. Researchers are hot on the trail of chemicals that could indicate PTSD in a blood test, says Kerry Ressler, a molecular scientist and psychiatrist at McLean Hospital of Harvard Medical School.
Treatments mostly aim to retrain the brain’s fear response. Many patients are given cognitive therapy, which teaches them to think differently about what happened and trains them to cope with triggers. Debra Kaysen of the University of Washington says severe symptoms recede in about four out of five patients following a dozen or so sessions. Other patients are given exposure therapy, in which they are confronted with the feared stimuli. Adults may be asked to describe a traumatic event in excruciating detail until it loses its potency; young children might play out what happened with toys. Virtual-reality simulations have been used on soldiers. One therapist compares the work to treating a burn victim: layer after layer.
Amit Etkin and colleagues at Stanford University are studying how the brain circuits that control fear can be tweaked with the aid of SSRIs (a class of drugs, some of which are used to treat depression or anxiety) and transcranial magnetic stimulation, in which an electromagnet held close to the scalp transmits magnetic pulses to the brain. They found that stimulating a part of the frontal lobe can reduce activity in the amygdalae, which could lessen the symptoms of PTSD. Within five years, thinks Dr Etkin, new therapies will be available, including applying brain stimulation or using drugs to enhance the effects of talk therapy. Better treatments for other anxiety disorders, which afflict a third of Americans, could follow.
Even if new treatments for PTSD take longer to develop than hoped, acceptance of PTSD’s inherently physical nature could encourage sufferers to seek help earlier. Rape victims in Dr Kaysen’s practice typically waited 20 years before turning to her; Dr Marmar has treated veterans of the second world war who had tried to cope with their nightmares for as long as 40 years.
In a freezer in Boston are 50 samples of brain tissue donated to the world’s first brain bank dedicated to the study of PTSD, set up by the Department of Veterans Affairs. More veterans and civilians, with and without the disorder, are filling in health questionnaires and pledging to donate brain tissue after death. Those who could not be healed themselves might help arm future generations against the same suffering, or perhaps, one day, help prevent it altogether.
Fear itself | The Economist
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