The human mind learns to respond to threats by our past experiences. Sometimes we identify threats in harmless situations. The addition of stress exacerbates this response. This has been the focus of researchers in a recent study.
In an experiment that liked an unpleasant stimulus with a stressful situation it was found that stress heightens the fear response of situations in our memories.
This relationship between past memories and heightened fear responses related to past experiences during times of stress is being studied to try better understand and treat conditions such as PTSD.