Eternal sunshine for the stressful mind

Negative emotional memories can be suppressed in the long-term with the help of drugs that regulate stress hormones, new research has shown. The findings, published in the Journal of Clinical Endocrinology & Metabolism, could lead to new treatments for sufferers of post traumatic stress disorders (PTSD).

Stress hormones such as cortisol are known to modulate memory retrieval. Both high and low levels of cortisol impair emotional memory retrieval. A collaboration between Lehigh University and McGill University have tested the effects of Metyrapone – a drug that inhibits cortisol secretion – on memory retrieval. The researchers tested 33 men, aged between 18 and 35, in an experiment based on three sessions.

In the first session (incidental learning), the participants were shown a computer-based series of slides depicting a story with neutral and emotional phases. A few hours later participants were asked to recall this information. Saliva samples of the participants were taken to find the cortisol levels at different times.

In the second session (retrieval phase), the same procedure was applied with the participants divided in three groups. One group received a single dose of the drug, one group had a double dose and the third were given a placebo. The experiments tested memory recall at the time when cortisol levels were expected to be at their lowest value.

The third session (delayed recall) involved the same procedure without the administration of the drug or the placebo.

The scientists found that there was a significant decrease in cortisol values when a double dose of Metyrapone was taken.

The double dose group also recalled significantly less emotional information than the placebo group at both retrieval and delayed recall phases, whereas there was little difference between the single and double dose groups. Overall, there was no loss of neutral information but there was an effect on emotional memory retrieval.

“Our findings may help people deal with traumatic events by offering them the opportunity to ‘write-over’ the emotional part of their memories during therapy,” said lead author Marie-France Marin.

The experimental conditions introduce some limitations to the validity of the results obtained. Firstly, only men were tested on and hence one cannot conclude the effects Metyrapone may have on women. Secondly, the drug was tested on perfectly healthy men so it may not have the same effect on patients suffering from PTSD or any other medical condition for which the drug may actually be required. Thirdly it is difficult to conclude whether the effects seen are due to the presence of Metyrapone or low levels of cortisol.