Stress after a traumatic event can cause a person to start practicing behaviors that are quite different from their usual self. Avoiding situations, persistent overwhelming anxiety and intense reactions to events might all suddenly become an everyday experience for post-traumatic stress patients.
Virtual reality has been used as a way to chip away at those responses, allowing the patients to more fully immerse themselves in a healthy life. Immersion therapy has shown to be a highly successful course for post-traumatic stress patients, but of course that leads to some difficulties. Mainly, it's pretty irresponsible to, say, set up a car crash so patients can explore the stimulus that's been causing them pain.
With virtual reality, however, patients can explore a safe atmosphere that might simulate the event they experienced. It might seem odd, but being confronted with the images of their trauma can trigger memories or emotional experiences; therapy is then used to confront and accept the event. Survivors of terrorist attacks, for instance, might "visit" a virtual town square, where a bus is blown up. Reacting to the experience, a patient would be asked to analyze and delve into their memories of the traumatic event they themselves were part of.