Tallying sleep's benefits can seem as endless as counting sheep. Now, researchers say they might have found another benefit of sleep — it may be a good time to calm fears.
A fear was reduced in people by repeatedly exposing them to the fear memory during sleep, according to a study published online Sunday in the journal Nature Neuroscience.
"It's a novel finding," says Katherina Hauner, the study's lead author. "We showed a small but significant decrease in fear. The bigger picture is that, perhaps, the treatment of phobias can be enhanced during sleep." Hauner conducted the research when she was a postdoctoral fellow in neurology at the Northwestern University Feinberg School of Medicine in Chicago.
The study included 15 healthy young adults who received mild electric shocks while viewing two faces. They were exposed to an odor when seeing each face and getting a shock. In doing so, the face and odor were associated with fear. When a subject was sleeping, an odor was continuously presented but without the associated faces and shocks. When the subjects woke up, they were shown both faces. Their fear reactions were lower for the face linked to the odor they smelled during their rest.
There may be an advantage to adding a nighttime component to exposure therapy, a treatment for phobias and post-traumatic stress disorder, says Hauner, assistant director of the Cognitive Neuroscience Laboratory at the Rehabilitation Institute of Chicago.
Exposure therapy involves exposing a patient to a feared object or situation without danger to reduce anxiety. A therapist usually uses this technique with a patient during the day.
It may be helpful for patients if they can experience changes in their fear responses during sleep when they are not aware of the process, Hauner says. In that way, they wouldn't have to go through confronting the feared object or situation as much as they would in current therapy, she says.
"This is a new area of research," she adds. Further testing could look at whether the approach would produce long-term effects, she says. Also, the study examined memories created in a lab so further research could look at whether the approach would have an effect on pre-existing fear memories, she says.
"The study is important and exciting because it's a reminder that sleep doesn't just improve or consolidate memory," says Mark Mahowald, an American Academy of Neurology member who was not involved in the research. "It can extinguish memories."
"The extinction of memory during sleep could be important for people with PTSD and chemical dependencies," says Mahowald, a professor of neurology at the University of Minnesota Medical School in Minneapolis. "Further research could look at relapse prevention."
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