Experiencing a second traumatic event may be the tipping point for an individual, as it may make them more likely to develop post-traumatic stress disorder (PTSD), based on new research in rats.
In their study, Cristina Alberini, PhD, a neuroscientist at New York University, and colleagues placed rats in a box lit on one side and dim on the other. Rats tended to prefer dark areas rather than lighted ones. When the rats entered the dark area, they received a shock on their feet.
The rodents’ memories and stress responses were temporarily inhibited after the shock, but soon returned to normal. However, after a second unexpected experience, the rats began to demonstrate anxiety and fear similar to what is seen in people with PTSD, the researchers reported in the Journal of Neuroscience.
The second shock was given in one of two places: Either the same dark area of the box, or in a completely different environment where it would be unexpected. If the shock was unpredictable, it led to PTSD-like behavior in the rats, but when it happened in the same vicinity as the first one, it didn’t agitate the rodents as much.
The researchers then wanted to see how the rats recalled their traumatic experience by placing them in the box again and seeing how long they stayed in the lit area before going into the dark area. While the rats who received low-intensity shocks largely avoided the darkened part, ones who were exposed to larger shock didn’t hesitate before going over to the dark side, an indication their memories were inhibited.
A single traumatic experience is enough to rattle people hard, but it rarely takes them down. In the face of subsequent ordeals, however, we become more vulnerable: a new study suggests that a second trauma has a critical role in leading to post-traumatic stress disorder (PTSD), a condition that can include flashbacks, nightmares and intense anxiety, enough to disrupt a person’s life.
When scientists gave rats one painful electric shock, the rodents’ memories and stress response temporarily became blunted but returned to normal as expected. But after a second unpredictable harrowing experience, the animals began to show fear and anxiety similar to what is seen in people with PTSD.