RIVERSIDE, CA – A new study could have significant implications for servicemembers suffering from insomnia related to post-traumatic stress disorder (PTSD).
Sleep researchers from University of California campuses in Riverside and San Diego found that a widely prescribed prescription sleep medication, zolpidem, intensifies recollection of and response to negative memories. 1
The National Institutes of Health study, published recently in the Journal of Cognitive Neuroscience, discusses the significance of sleep spindles, defined as bursts of brain activity that last for a second or less during a specific stage of sleep, in developing emotional memory.
“We know that sleep spindles are involved in declarative memory — explicit information we recall about the world, such as places, people and events,” said lead author Sara C. Mednick, assistant professor of psychology at UC Riverside.
Earlier research focused on sleep spindles and rapid eye movement (REM) sleep and not their role in emotional memory, she said.
Previous studies by Mednick and colleagues found that zolpidem, marketed as Ambien by Sanofi Aventis, enhanced the process of consolidating information from short-term to long-term memory. It was touted as the first study to show that sleep can be manipulated with pharmacology to improve memory.
For the current research, 28 men and women between the ages of 18 and 39 who were normal sleepers were given zolpidem, sodium oxybate (Xyrem) and a placebo, allowing several days between doses to allow the compounds to leave their bodies. Participants viewed standardized images known to elicit positive and negative responses for one second before and after taking supervised naps.
Study authors noted that participants recalled more images that had negative or highly arousing content after taking zolpidem.
“I was surprised by the specificity of the results, that the emotional memory improvement was specifically for the negative and high-arousal memories, and the ramifications of these results for people with anxiety disorders and PTSD,” Mednick said. “These are people who already have heightened memory for negative and high-arousal memories. Sleep drugs might be improving their memories for things they don’t want to remember.”
The study noted that the effects of benzodiazepines on sleep are similar to those of zolpidem, adding that, while VA and DoD clinical guidelines now recommend against the routine use of benzodiazepines to treat PTSD, their use was widespread between 2003 and 2010 among PTSD patients. In addition, the authors pointed out the Air Force uses zolpidem as one of the prescribed “no-go pills” to help flight crews calm down after taking stimulants to stay awake during long missions.
“In light of the present results, it would be worthwhile to investigate whether the administration of benzodiazepine-like drugs may be increasing the retention of highly arousing and negative memories, which would have a countertherapeutic effect,” they wrote. “Further research on the relationship between hypnotics and emotional mood disorders would seem to be in order.”
1. Mednick SC, McDevitt EA, Walsh JK, Wamsley E, Paulus M, Kanady JC, Drummond, SP. The critical role of sleep spindles in hippocampal-dependent memory: a pharmacology study. J Neurosci. 2013 Mar 6;33(10):4494-504. doi:10.1523/JNEUROSCI.3127-12.2013. PubMed PMID: 23467365