Key Study: Cortisol and Memory (Buchanan and Lovallo, 2001)

Travis Dixon Biological Psychology, Cognitive Psychology, Post-Traumatic Stress Disorder 4 Comments

The effects of cortisol release on memory formation could explain why people who experience traumatic events (like war) have long-lasting and intrusive memories of the trauma.

This study can be found in Chapter 4 of the Student’s Guide.


Studies conducted before this experiment in 2001 showed that cortisol can have a detrimental effect on memory. Animal studies, however, had shown the opposite: stress can improve memory.  This was the first study (at the time) that investigated the influence of cortisol on emotional memory in humans. It’s important to remember that cortisol is released by the adrenal gland during the stress response. So if we’re feeling stressed our amygdala will trigger the HPA axis and cortisol will be released. This experiment tested how that release of cortisol might affect memories of emotional information. While this study looked at memory of both positive and negative emotional material, understanding how stress affects memory could help us understand memory-related symptoms of PTSD, such as intrusive memories.

Methodology and Results

  • 48 participants (24 male/female)
  • Healthy participants (screened for psychiatric and neurological conditions)
  • Double-blind, independent samples design
  • Participants received 20mg of cortisol or a placebo
  • They were then shown a range of images, either pleasant scenes (eg. nice food, mountain scenery), unpleasant (e.g. disfigured people, threatening weapons) scenes or neutral scenes (e.g. a bicycle). The images were shown to participants on a TV.
  • Participants ranked how emotionally arousing they found the images.
  • One week later the participants’ memories of the images were tested (they were not told about the memory test beforehand).
Person Pouring Out Pills On Hand

The cortisol and placebo tablets given to the participants were identical.

The results showed that both groups remembered the emotionally arousing images better than the neutral images. The results also showed that the cortisol group remembered significantly more emotionally arousing images than the control group. The strongest effect was found in cued memory – when participants where given a category title (e.g. injured people, food, sports) and asked to recall the images.


  • How does this study show emotion influences cognition (memory)?
  • How can this study show ethical considerations in research on hormones and/or the effects of emotion on cognition?
  • How can this study show the use of research methods (experiments) to study hormones and/or the effect of emotion on cognition?
  • How can this study provide explanations for intrusive memories of traumatic events (a symptom of PTSD)?
  • How can this study provide evidence for an evolutionary explanation of behaviour (stress enhancing memory consolidation of emotional events)?
African American Mother and Child

When applying this study to explain PTSD we could focus on the effects of stress on memory consolidation. However, it’s important to note that cortisol enhanced the memory of positive AND negative emotionally arousing material.

Critical Thinking Considerations

  • Emotion and cognition: generalizability: what real life conditions might moderate the effects demonstrated in this study?
  • Ethical considerations: what are the potential negative impacts of this research on participants? How could these negative effects be reduced by following ethical guidelines?
  • Research methods: What are the limitations of using an experimental design in this experiment to study the effects of stress hormones on cognition?
  • PTSD: What are the limitations in using this study to explain symptoms of PTSD, such as intrusive memories?


Buchanan, Tony W., and William R. Lovallo. “Enhanced Memory for Emotional Material following Stress-level Cortisol Treatment in Humans.” Psychoneuroendocrinology 26.3 (2001): 307-17.

Link to original article here.

Comments 4

  1. Pingback: Teaching Tip: 3 ways to save hours of teaching time – IB Psychology

  2. Thank you very much for the IB PTSD resources.
    I’ve also been using your IB psychology textbook which has been an excellent source of guidance.
    However, I have a doubt when correlating cortisol with memory in patients with PTSD. On the one hand, according to the results of Buchanan and Lovallo’s study above, increased levels of cortisol enhanced emotional memory, thereby allowing a person to remember the stressful and potentially dangerous situation they were in, which is an important survival function. On the other hand though, in the textbook, you have also included a section on how increased levels of cortisol can damage the hippocampus, which is associated with learning and memory. So, this side of the argument would claim that increased cortisol could mean damaged memory/ amnesia of the traumatic event? In conclusion, does cortisol reinforce the memory of the event or delete it from our memory??

    Would you be able to advise me on how to interpret both sources of information such that I can understand which evidence to use when or how? Thank you very much.

    1. Post

      Hi Sahana,
      Great question. As with all good questions, the answer is “it’s complicated.” Firstly, let’s talk about cortisol and memory without worrying about PTSD (as this covers the hormones and behaviour topic in the syllabus). The studies you mention (and those in the book) suggest that acute (short-term) stress will release cortisol and improve memory (e.g. of a traumatic event), but chronic (long-term) stress (e.g. experiences in war) will damage the hippocampus which may negatively affect memory. Thus, cortisol’s effect on memory could be positive or negative, depending on if the stress (and thus release of cortisol) is acute or chronic. In terms of PTSD, I would say that not every person’s experience of PTSD is the same, so the above explanations of cortisol’s effects could explain why some people can’t remember details of their trauma, and maybe why others can’t NOT remember their trauma. It’s important to note, to, that studies like Gilbertson’s twin study (in the book) and numerous others, suggest that a small hippocampus is a risk factor for developing PTSD, so that could be another factor explaining the memory problems symptom.

      Does this help? As I said, it’s complicated. What makes it even more complicated, is that a common finding with people wiht PTSD is that they have LOWER levels of cortisol than normal. This surprised everyone!

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