Understanding the interactions between the anxiety hormone cortisol and long term memory is a key part of explaining and preventing Post-Traumatic Stress Disorder (PTSD). However, previous studies have been inconclusive about cortisol's role in enhancing memory; certain studies have found that the stress hormone does in fact increase memory, while others have found no relation. A recent study, published earlier this month in Neuroscience journal, works at explaining this discrepancy, and may have found that the interaction between anxiety and memory is a more complex one than previously anticipated.

The study examines the relationship between cortisol, memory, and a second anxiety hormone: norepinephrine. Norepinephrine, similar to adrenaline, is a hormone which increases heart rate and facilitates a fight-or-flight response. The release of the hormone is triggered by anxiety-ridden situations, such as when individuals feel threatened or when they experience highly emotional reactions to events. The results of the study could show that cortisol only has an effect on strengthening memory when norepinephrine is also activated, and may have important implications for the future of PTSD research.

Studying the Link Between Memory and Anxiety

Researchers from Arizona State University and the University of California, Irvine, conducted the study by showing 39 women, aged 18-35 years old, 144 images from the International Affective Picture set. This image set is a standardized album created by researchers, used to provoke a wide range of emotional responses. Prior to viewing the images, half of the women were administered a placebo drug, and the other half were given a dose of hydrocortisone, a drug used to stimulate anxiety. Saliva samples were taken both before and after the women viewed the image, and the participants were asked to describe their emotions at the time of viewing. Then, one week after the study was conducted, an unannounced recall test was conducted in order to test long-term memory impact of the study.

After examining the results of the recall test, the researchers found that women whose cortisol and norepinephrine levels increased while studying negative images were much more likely to accurately remember these images. The study concluded that “negative experiences are more readily remembered when an event is traumatic enough to release cortisol… and only if norepinephrine is released during or shortly after the event." The research indicated that while cortisol does, in fact, have a significant influence on strengthening memory, this effect only comes into play if the secondary anxiety hormone norepinephrine is also released.

The Results

Sabrina Segal, head author of the study, believes that the study “provides a key component to better understanding how traumatic memories may be strengthened in women...because it suggests that if we can lower norepinephrine levels immediately following a traumatic event, we may be able to prevent this memory enhancing mechanism from occurring, regardless of how much cortisol is released." While further studies are needed in order to examine the interactions of these anxiety hormones in men, for now this research contributes to our understanding of the underlying mechanisms behind PTSD, and goes far to explain the relationship between anxiety and memory.

Date of original publication:


S.K. Segal, R. Simon, S. McFarlin, M. Alkire, A. Desai, L.F. Cahill. Glucocorticoids interact with noradrenergic activation at encoding to enhance long-term memory for emotional material in women. Neuroscience, July 2014. DOI: 10.1016/j.neuroscience.2014.06.059