A trauma trigger is an experience that triggers a traumatic memory in someone who has experienced trauma. A trigger is thus a troubling reminder of a traumatic event, although the trigger itself need not be frightening or traumatic.The term 'trauma trigger' is not used or recognised in scientific literature but is related to Post Traumatic Stress Disorder.Triggers can be quite diverse, appearing in the form of individual people, places, noises, images, smells, tastes, emotions, animals, films, scenes within films, dates of the year, tones of voice, body positions, bodily sensations, weather conditions, time factors, or combinations thereof[citation needed]. Triggers can be subtle and difficult to anticipate, and can sometimes exacerbate post-traumatic stress disorder, a condition in which sufferers cannot control the recurrence of emotional or physical symptoms, or of repressed memory. A trauma trigger may also be referred to as a trauma stimulus or a trauma stressor.A trauma trigger can manifest in a variety of forms from exhibiting a changed mental state or physical reactions[citation needed]. A person that is experiencing a trauma trigger may not even know this is happening[citation needed][vague].