Posttraumatic Stress Disorder and Brain Laterality

I’ve just received an intriguing article from an individual who’s really been through the mill with an array of psychiatric problems going back to childhood.

The last diagnosis that he attracted was posttraumatic stress disorder (PTSD), and he seems to have cured himself by a combination of omega-3 fatty acids and learning to play the banjo left-handed.

This may sound like a bit of an odd claim, but although the writer did not realize it, there is actually some solid science behind his observation.

For years now we have known that if someone is paralyzed down one side after a stroke, binding the good arm or leg leads to rapid reorganization in the cerebral cortex, as a result of which the paralyzed arm or leg may begin to regain function.

One of the most potent ways to improve the functioning of regions of the brain is to try doing things with the opposite hand: if your are right-handed, brushing your teeth or writing with your left hand or using your knife and fork the other way round can all be very illuminating, and can help train your brain. A common tactic in couple’s therapy is to get people to change some habits, like switching the sides of the bed on which a couple sleeps.

The hippocampus of the brain is involved in many functions, but key amongst them is the laying down of short-term memories. People with several stress-related psychiatric disorders, including PTSD, borderline personality disorder with early abuse, depression with early abuse, alcoholism and dissociative identity disorder all have smaller hippocampi, presumably because this part of the brain is exquisitely sensitive to cortisol: high levels can damage and destroy hippocampal cells. Antidepressant medications and some types of cognitive training are thought to lead to the growth of new cells in the hippocampus. It is also possible that having a small hippocampus may predispose someone to the development of PTSD. There is also some evidence that mixed lateral preferences and parental left-handedness may all predispose someone to the development of PTSD.

In PTSD, the left hippocampus and two other brain regions: the left anterior cingulate cortex and both sides of the insula are all smaller than normal. Regions of this small left hippocampus associated with episodic and autobiographical memory is activated by stimuli that wouldn’t have much effect in people without the problem. Some researchers have also found that if the right hippocampus is smaller and more active, it correlates with the severity of PTSD symptoms.

Adults with PTSD have a higher incidence of mixed laterality with respect to handedness than the rest of the population. This has recently also been found in children: there is a positive correlation between PTSD symptom severity and mixed laterality. This strongly suggests that neurological abnormalities may be related to the severity of symptoms in PTSD.

In PTSD, the right amygdala, a region involved in fear and rapid emotional learning and processing, is smaller than the left. In healthy volunteers it’s the same on both sides.

When people with PTSD recall the traumatic event, especially if it involved assault, they over-activate the right hemisphere of the brain. It is not just cerebral blood flow: recent experimental work has shown that PTSD may be associated with a functional asymmetry of the brain, which favors the right hemisphere.

There are actually a number of therapeutic techniques that involve trying to switch the way in which the hemispheres interact. EMDR (which the writer had tried) is one. It is also amongst the techniques developed by Paul Dennison to aid learning.

I also wonder whether the writer has accidentally happened upon a method for treating psychological reversal.

I do wish the writer well, and I also hope that some of my colleagues in research might be interested in exploring some of these training techniques in PTSD.