The tablet form of the stress hormone cortisol could accelerate the process of forgetting intrusive memories, when given immediately after a traumatic event, finds a new study by UCL researchers.

The research, published in Translational Psychiatry, found that hydrocortisone (30mg)—an anti-inflammatory drug used to treat conditions such as arthritis—acts to weaken the emotions that underly painful memories, such as those experienced in post-traumatic stress disorder (PTSD).

The team tested the medication on 120 healthy participants. 60 were given hydrocortisone and 60 were given a placebo drug.

They found that the group who were given hydrocortisone a few minutes after being shown several very upsetting videos, seemed to "forget" the event more quickly compared to those who had been given a placebo drug.

The researchers also found that men and women responded differently to the drug, depending on the levels of sex hormones in their system. For example, men who had high levels of estrogen seemed to have the fewest upsetting memories for a week after watching the video.

However, women showed the opposite effect and high levels of estrogen seemed to make them more susceptible to involuntary bad memories if they were treated with hydrocortisone.

Lead author, Ph.D. candidate Vanessa Hennessy (UCL Psychology & Language Sciences), said, "Persistent distressing, involuntary or 'intrusive' memories are a core feature of PTSD. Unlike other psychological disorders, the onset of PTSD caused by a single trauma can reliably be traced back to the occurrence of a specific, often life-threatening event that generates long-lasting intrusive memories.

"The findings reported here build on previous studies that target the emotions that underlie involuntary memory, with the aim of reducing how often they happen and how vivid they are—whilst still leaving the ability to recall the memory voluntarily.

"Our work shows how important it is to do careful experiments with healthy people to work out whether and how a drug like hydrocortisone could work. After all, our results seem to show that there might be conditions that make the drug harmful in some people."

The researchers hope that their findings can be used by clinical researchers to design more targeted treatments for men and women with PTSD, by using preventative measures based on individual hormone profiles and that target intrusive memories.

Currently hydrocortisone has only been found to be effective when given to trauma patients in the hours directly following trauma or before sleep when the memory is consolidated. However, researchers hope that similar treatments with an added behavioral element could speed up the natural forgetting process and limit long term psychological distress within a longer time-frame, in the future.

Study limitations: Although using traumatic videos is an ethical way to elicit intrusive thoughts in healthy people, one concern is that the resulting memories won't mirror those seen following real-life traumas.