Many people with PTSD experience frequent cognitive distortions, such as catastrophic thinking. Cognitive distortions refer to unpleasant thoughts that are extreme, exaggerated, and/or not consistent with what is actually going on in the real world. As a result, cognitive distortions can have a negative influence on our mood and eventually lead to unhealthy behaviors. Catastrophic thinking in particular refers to a tendency to expect the worst to happen without considering other alternative outcomes that are more likely to happen.
It would make sense that someone would develop catastrophic thoughts following exposure to a traumatic event. After someone experiences a traumatic event, he receives verification that the worst can actually happen. A traumatic event destroys assumptions that we often make about the world, such as that the world is a safe place, or "it won't ever happen to us." After a traumatic event, our body and mind try to ensure that we will never be placed in a dangerous situation again, and it tries to prepare us for future traumatic events. One way it might do this is by bringing up catastrophic thoughts. Unfortunately, these catastrophic thoughts don't present all other possible options -- they only present the worst possible case. As a result, these thoughts can be paralyzing, leading to extreme anxiety, avoidance, and isolation. They may make a person feel as though he is constantly in danger and nothing is safe.
Catastrophic thoughts can be debilitating. Fortunately, there are steps you can take to address catastrophic thoughts. Some healthy ways of coping with catastrophic thoughts can be found in this article.