People who suffer from chronic stress may have a predisposition to mental disorders, according to a recent study published in the journal Molecular Psychiatry.
Professor Daniela Kaufer and her colleagues at the University of California, Berkeley found that chronic stress causes brain abnormalities, like more myelin-producing cells and fewer neurons. This overproduction of myelin, or white matter, in certain parts of the brain upsets the balance and timing of communication.
Such disturbances in the brain are present in mental illness such as posttraumatic stress disorder (PTSD).
Kaufer explained that as the connections between the hippocampus and the other part of the brain are strengthened, a person's stress increases.
"You can imagine that if your amygdala and hippocampus are better connected, that could mean that your fear responses are much quicker, which is something you see in stress survivors," she said in a press release.
"On the other hand, if your connections are not so good to the prefrontal cortex, your ability to shut down responses is impaired. So, when you are in a stressful situation, the inhibitory pathways from the prefrontal cortex telling you not to get stressed don't work as well as the amygdala shouting to the hippocampus, 'This is terrible!' You have a much bigger response than you should."
This study is the first look into unraveling the mechanism responsible for long-lasting changes in brain structure.
Using stressed out lab rodents as their subjects, Kaufer and researchers discovered that stem cells in the hippocampus mature into a type of glial cell called an oligodendrocyte, which produces the myelin coating of nerve cells. These oligodendrocytes thereby could cause long-term or permanent brain alterations that may lead to mental problems later in life. Oligodendrocytes also help form synapses and control the growth pathway of axons, both functions that aid in cell communication.
Chronic stress could also affect learning and memory because it decreases the number of stem cells that mature into neurons.
