People who experience chronic stress due to bullying or a tough job also run a higher risk of memory loss, according to a new study published in The Journal of Neuroscience.
People who are constantly stressed by bullying or a difficult job may be prone to short-term memory loss, too.
Previous studies have connected chronic stress with long-term anxiety.
Researchers led by Jonathan Godbout, associate professor of neuroscience at Ohio State University, investigated the relationship between prolonged stress and short-term memory loss in mice.
Ultimately, the researchers hope the findings will help people who live with ongoing stress.
The team had mice get used to a maze with an escape hole. They then exposed the mice to repeat visits from a larger, aggressive intruder mouse.
Mice that repeatedly had to confront the intruder found it harder to remember the location of the escape hole, whereas the mice that were not stressed were able to find it.
Memory loss matched by immune response
The problems resolved within 28 days, but until then, the mice showed evidence of social avoidance, a measure of depressive behavior.
The inability to remember coincided with measurable changes in the mice's brains. Immune cells, or macrophages, appeared in the brains of the stressed mice, indicating that inflammation had resulted from the immune system's response to the stress.
Moreover, focus on the hippocampus, a hub of memory and emotional response, revealed shortfalls in the development of new neurons at 10 and 28 days after the stressful period ended.
The team concludes that the short-term memory loss is linked to brain inflammation and the immune system.
John Sheridan, associate director of Ohio State's Institute for Behavioral Medicine Research, explains: "Stress releases immune cells from the bone marrow, and those cells can traffic to brain areas associated with neuronal activation in response to stress. They're being called to the brain, to the center of memory."
This experience of repeated dominance by an alpha mouse and persistent social defeat will be familiar to many people who live with chronic psychosocial stress.
The scientists hope that a better understanding of stress and cognitive and mood problems could help create strategies for those whose daily lives involve anxiety, depression and ongoing problems such as post-traumatic stress disorder. One solution could be to find a way to interrupt the inflammation.
"The impact on memory and confirmation that the brain inflammation is caused by the immune system are important new discoveries. It's possible we could identify targets that we can treat pharmacologically or behaviorally."