New research suggests the stress hormone cortisol strengthens memories of traumatic or scary experiences.
The hormone appears to influence initial memory formation and also affects subsequent memory reconsolidation that occurs when people look back at an experience.
The findings from cognitive psychologists at the Ruhr-Universität Bochum have been published in the journal Neuropsychopharmacology.
Typically, strong memories of stressful experiences occur frequently, but they usually fade away over time. People suffering from anxiety or post-traumatic stress disorder, however, are affected by terrifying memories that haunt them again and again.
Research has shown that the stress hormone cortisol has a strengthening impact on the consolidation of memories, i.e. the several-hour process in the course of which a memory is formed immediately after the experience.
The researchers from Bochum discovered that cortisol effects memories in humans also during the so-called reconsolidation, i.e. the consolidation of memories occurring after memory retrieval. They found that cortisol can enhance this process.
“The results may explain why certain undesirable memories don’t fade, for example in anxiety and PTSD sufferers,” said Prof. Dr. Oliver Wolf.
If a person remembering a terrifying event has a high stress hormone level, the memory of that specific event will be strongly reconsolidated after each retrieval.
In the study, researchers collected data from subjects on three consecutive days. Shira Meir Drexler, a Ph.D. student at the International Graduate School of Neuroscience in Bochum led the experiment.
On the first day, the study subjects learned an association between specific geometric shapes and an unpleasant electric shock. On the second day, some of the participants were given a cortisol pill, others a placebo.
Subsequently, they were shown one of the geometric shapes associated with the electric shock.
On the third day, the memory for the geometric shapes was tested. Participants who had taken cortisol exhibited strong memories of the fear-associated shape. Researchers found proof of this association as the subjects displayed a heightened skin conductance, an established measure for emotional arousal.