Stress negatively affects brain development and may impair spatial working memory in children, according to a new study.
Previous research has linked both acute and chronic stress to changes in a part of the brain called the prefrontal cortex, a part of the brain involved in higher level cognitive abilities, in animals.
However, the latest findings, due to be published in the June 6 issue of the Journal of Neuroscience, also link exposure to stress to more issues with certain types of cognitive processes.
Researchers at the University of Wisconsin–Madison found that children who had experienced more intense and lasting stressful event in their lives scored significantly lower on tests measuring their spatial working memory and had more trouble navigating tests of short-term memory such as finding a token in a series of boxes.
Brain scans revealed that the anterior cingulate, a portion of the prefrontal cortex assumed to play key roles in spatial working memory, took up less space in children with more exposure to stressful situations.
"These are subtle differences, but differences related to important cognitive abilities" researcher Jamie Hanson, a UW–Madison psychology graduate student, said in a statement.
While there were noticeable differences in the brains of children exposed to greater stress, researchers noted that they may not be irreversible.
"We're not trying to argue that stress permanently scars your brain. We don't know if and how it is that stress affects the brain," Hanson said. "We only have a snapshot — one MRI scan of each subject — and at this point we don't understand whether this is just a delay in development or a lasting difference. It could be that, because the brain is very plastic, very able to change, that children who have experienced a great deal of stress catch up in these areas."
Researchers determined stress levels by interviewing children ages 9 to 14 and their parents, and based their measurements on a collection of biographical data illustrating stressful events from slight to severe.
"Instead of focusing in on one specific type of stress, we tried to look at a range of stressors," Hanson explained. "We wanted to know as much as we could, and then use all this information to later to get an idea of how challenging and chronic and intense each experience was for the child."
Surprisingly, researchers found little correlation between cumulative life stress and age, meaning that children who had several more years of life in which to experience stressful episodes were no more likely than their younger peers to have accumulated a length stress resume, whereas puberty typically corresponds with greater stress exposure.
Children with greater stress exposure also had lower white and gray matter volumes, which varied depending on the intensity of stress.
Researchers explain that white matter is like the long-distance wiring of the brain and allows separate parts of the brain to communicate to one another. Gray matter, on the other hand, "does the math" and is responsible for processing and using information that gets shared along the white matter connections.
"For both gray and white matter, we actually see smaller volumes associated with high stress," Hanson said. "Those kinds of effects across different kinds of tissue, those are the things we would like to study over longer periods of time. Understanding how these areas change can give you a better picture of whether this is just a delay in development or more lasting."
Hanson said that the recent findings could lead to better treatment and diagnosis for children who have experienced intense stress.
"There are groups around the country doing working memory interventions to try to train or retrain people on this particular cognitive ability and improve performance," Hanson concluded. "Understanding if and how stress affects these processes could help us know whether there may be similar interventions that could aid children living in stressful conditions, and how this may affect the brain."