If a memory causes physical distress, does that necessarily mean that the event you're remembering actually happened? Interestingly, to answer this question, the researchers studied people who reported being abducted by aliens. After all, most people would agree that the odds that these folks were actually abducted are pretty slim.
The scientists asked the participants to describe their abduction memories, along with a non-abduction-related stressful memory. Then the researchers converted these descriptions into narratives that they played back to the participants while monitoring their heart rate, sweat production, and facial muscle tension.
It turned out that, from a physiological perspective, the participants had similarly strong reactions to the alien abduction story and to the non-abduction- related stressful memory. What these observations suggest is that having a strong physical reaction to a memory doesn't necessarily make the event you're remembering true, it just means that the memory itself is traumatic.