Imprinting Trauma on the Brain

Health Writer

We all wonder about why some people experience long-term anxiety after a traumatic event while others seem to "get over it" much quicker and don't suffer for months or years. Imagine two people who witness a terrible car accident. One may have trouble sleeping, flashbacks and other anxiety symptoms for many years. He may be afraid of getting into a car or suffer from panic attacks when driving or even being a passenger in the car. The other person feels anxious for a shorter period of time, somehow able to compartmentalize the event and move on with their life. Why does one person develop post traumatic stress disorder and the other does not?

Scientists at the University of Bonn in Germany completed a study to find out what may cause some people to be unable to let go of the anxiety after a traumatic event. The researchers believe that dynorphins, a substance released in our brain to calm emotions, may help some people to move on from a traumatic event and the absence of this substance cause others to experience anxiety for a long time after.

The first experiment the researchers completed used mice.  Some of the mice had the gene which creates dynorphins disabled. The animals were then given (brief and unpleasant) electric shocks. The mice which had a normal amount of dynorphins showed signs of anxiety for a brief period of time after the electric shock. Those without the ability to create this substance continued to show anxiety symptoms over a longer period of time.

The researchers then looked at how humans react to the dynorphin gene. Thirty-three participants were divided into two groups, one group who naturally released higher levels of dynorphins. All of the participants watched blue and green squares appear in an imaging technology. When the green squares appeared, participants received a unpleasant stimulus on the hand using a laser. Researchers monitored stress levels throughout the test by observing sweat on the skin as well as through brain scans. The participants then went through the test without the unpleasant stimulus.

Both groups of participants were monitored for how long stress reactions occurred after the laser stimulus ended. As with the mice, those with lower dynorphin activity experienced feelings of stress and anxiety for longer than those with higher levels of activity.

The scientists hope that through better understanding of how dynorphins work and impact long-term stress from a traumatic event new strategies can be developed for treatments for those experiencing trauma.


"When Anxiety Won't Go Away," 2012, Andras Kilkei Gorzo, Andreas Zimmer, Henrik Walter, The Journal of Neuroscience