We now know that post-traumatic stress disorder is caused by changes in the brain. (Another way to look at it is to say that PTSD causes changes in the brain: either way it is possible to see that the brains of PTSD sufferers look different from those of non-sufferers.)
So, for example, the hippocampus is a part of the brain that helps an individual to record new memories and retrieve them later. In PTSD sufferers, the hippocampus is smaller, which suggests that it may not be working properly to process memories. This may be why people with PTSD experience flashbacks – it’s as if the traumatic event is still real and present rather than in the past.
Similarly, the amygdala, helps us process emotions and is also linked to fear responses. In PTSD patients, the amygdala may be hyperactive, making them feel extra panicky and fearful when they see something that reminds them of the trauma (such as returning to the hospital where they gave birth, for example).
A newly published piece of research looked at the thalamus – a structure that sends and receives information to and from different bits of the brain. Using mice, the study looked at something called the posterior paraventricular thalamus (pPVT), which receives messages from the brain’s pain-sensing structures. When the scientists taught mice to fear an electric shock, the pPVT became more active and sent the information to the amygdala, which in turn increased activity.
In other words, the communication between this bit of the thalamus and the amygdala is crucial to learning fear responses.
The study then looked at BDNF – a nerve growth factor that can help the brain repair itself when it’s been damaged. When the scientists injected BDNF into the mice’s amygdala, the mice learned to become fearful more quickly – just a mild electric shock rather than several shocks made them learn fear. Similarly, when they decreased levels of BDNF, the mice were unable to learn fear.
So it looks as if an excess of BDNF may be the key to understanding why – or at least how – PTSD sufferers experience disproportionate feelings of fear.
This is all rather technical – and what I’ve written is a simplification of an already simplified explanation. It would be wrong to jump to any conclusions based on a single study. But the point is that this kind of research is able to show us the brain at work. Like any other organ, the brain can malfunction – and if we can understand how it malfunctions, then there is hope that we can also repair it.