Dr. Daniela Kaufer and her colleagues at the University of California, Berkeley, have found that Chronic stress triggers long-term changes in brain structure and function. (Molecular Psychiatry 2014) Kaufer’s research proposes a mechanism that could explain some changes in the brains of people with PTSD. She found that PTSD patients develop a stronger connectivity between the hippocampus and the amygdala (the seat of the brain’s fight or flight response). And, they develop a lower connectivity between the hippocampus and the prefrontal cortex, which moderates our responses. For the most part, it has been generally accepted that brain changes as a function of stress are based on repeated or chronic stress.
Recently, however, a research group at the University of Milan working with animal models found that even a single stressful event may cause long-term consequences in the brain. Dr. Maurizio Popoli and his colleagues (Molecular Psychiatry, 2016) found that a 40-minute protocol of stress enhances the release of glutamate, which is the major excitatory transmitter in the prefrontal cortex (PFC). New findings show that the enhanced glutamate release is sustained for at least 24 hours after the short stress protocol. AND, they found significant atrophy of apical dendrites after the 24 hours. Previous findings had suggested that dendrite atrophy is only seen after weeks of chronic stress.
These results may completely change the traditional distinction between chronic and acute stress. The University of Milan findings indicate that a single exposure to stress may cause a release of glutamate that lasts for at least 24 hours. And, the consequences are that the dendrite atrophy begins after only 24 hours and can last up to 2 weeks after the single stress protocol of 40 minutes. The authors relate these stress-related brain changes to PTSD and other stress-related disorders.
Dr. Kaufer and her colleagues also found that chronic stress generates more myelin-producing cells and fewer neurons than normal. This results in an excess of myelin – white matter – in some brain areas. The excess of white matter with fewer neurons disrupts the balance and timing of the internal communication within the brain.
Just how chronic and now acute stress creates these long-lasting changes in brain structure is still a mystery. The findings of brain-related changes secondary to acute and chronic stress hold the hope of finding new therapies that can reduce the risk of developing mental illness after stressful events.