Although it is well-known that traumatic events like sexual assaults or terrorist bombings can cause posttraumatic stress disorder (PTSD), sufferers from this disorder often complain that no one really understands what they are going through. This is probably due to a unique and poorly understood symptom of PTSD, the traumatic flashback. In one way flashbacks are just very vivid, detailed, and emotional memories in which someone sees, hears, feels, or even smells specific frightening or horrible moments that occurred. But unlike ordinary memories, flashbacks are an experience in which the traumatic event is replayed in the person’s mind as though it were happening all over again in the present. In the most extreme form the person becomes lost in the memory and loses all sense of contact with the world around them. More commonly, the person knows where they are but has a powerful sense that the event is happening again, even though logically they know this cannot be true. This is an unusual form of memory and one that is hard to understand if you have not experienced it yourself.

Flashbacks can arise in many situations where the person has an intense fear of death, serious injury, or violation, including medical crises such as a heart attack. Terrifying delusions and hallucinations, which may occur to intensive care patients given powerful drugs, can also give rise to traumatic re-experiencing. Although this type of memory has been recognised since the 19^th century, flashbacks have until recently only been of one of many symptoms of PTSD. This is due to change in 2018 with the release of the World Health Organisation’s International Classification of Diseases 11th revision. This proposes that flashbacks are one of only six core symptoms of PTSD and will help people worldwide to recognise, treat, and research the disorder.

What are flashbacks? They appear to be produced by a memory system that captures detailed images of what we see, hear, and sense. Unlike our conscious memory system, with which we choose what we are and are not interested in remembering, these images are captured automatically and come to mind automatically when we come across reminders. The images usually decay rapidly, except in situations of extreme fear or horror. These are times when our conscious memory system works poorly. Attention tends to be restricted and focused on the main source of danger, so that little is consciously taken in about the wider scene and what there is may contain gaps and be disorganised. Now the image-based memory system provides a more enduring and detailed record of the event, retaining information that may be vital for future survival.

The image-based memory system is simple and robust. This is a strength as it continues to function well during traumatic events. Its weakness is that it is incapable of including information about where and when the images were captured. So when images of the traumatic event are triggered by reminders they are experienced as flashbacks in which the brain is tricked into reacting as though the event were really happening again now. This causes the body to react too, whether by making the heart pound and the hands sweat, or by inducing paralysis and dread. Flashbacks are thus a normal response to a traumatic event, and they usually begin to die down quickly. In PTSD, however, this recovery process fails to occur and flashbacks continue with undiminished force. The sufferer continues to live in a world of extreme subjective danger, even though to outside observers the danger appears to be past.

Chris Brewin
Clinical, Educational & Health Psychology,
University College London

Publication

Re-experiencing traumatic events in PTSD: new avenues in research on intrusive memories and flashbacks.
Brewin CR
Eur J Psychotraumatol. 2015 May 19

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