Intrusive memories are unwanted, involuntary recollections of a traumatic event that enter a person’s consciousness unexpectedly, often with vivid sensory detail and a sense that the event is happening again. They are one of the hallmark symptoms of post-traumatic stress disorder (PTSD) and are commonly reported by cardiac arrest survivors and their family members.
What intrusive memories feel like
Unlike ordinary memories that a person chooses to recall, intrusive memories feel as if they force themselves into awareness. They may be triggered by a sensory cue (a sound, a smell, a visual image, a physical sensation) that in some way resembles part of the traumatic event. For survivors, triggers might include the sound of a siren, the appearance of a hospital corridor, a tight sensation in the chest, or seeing a defibrillator. When triggered, the person may re-experience the event with great emotional intensity.
Who can be affected
Intrusive memories after cardiac arrest are not limited to the person who experienced it. Bystanders who performed CPR, family members who witnessed the arrest, and people who arrived on scene can all develop intrusive memories. The traumatic memory is not always of the cardiac arrest itself: for survivors who were unconscious, the intrusive memories may relate to the period in hospital, including frightening experiences in intensive care.
Why they occur
Trauma memories are processed differently from ordinary memories. During a highly stressful event, the brain encodes sensory and emotional details intensely but without the normal contextual framework. This means the memory is not stored in the same way as a narrative from the past, making it more likely to be triggered involuntarily.
Treatment
Intrusive memories are treatable. Trauma-focused cognitive behavioural therapy (CBT) and eye movement desensitisation and reprocessing (EMDR) are the most evidence-based treatments for trauma-related intrusive memories. A GP can refer to appropriate services.
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