How does the brain handle long-term stress?

People differ enormously as to what they consider to be stressful and how they respond to it. In general, short periods of moderate stress can actually be a good thing for the brain.

For example, riding a roller coaster or watching an exciting movie sharpens our sensory and memory systems. In response to short-term stress, cells in the hippocampus — a region central to learning and memory — become more active. At the same time, there is an increase in the release of the brain chemical dopamine in the brain’s reward pathway, which is central to pleasure. These changes leave us feeling good and alert. What do we call moderate and transient stress? Stimulation. 

The brain responds differently to chronic stress, such as years of job insecurity or money worries. Too much stress causes changes in how hippocampal cells function. Chronic stress leaves cells in the hippocampus more vulnerable to injury, and fewer new cells are born. With severe, prolonged stress, hippocampal cells even die. Studies have shown loss of hippocampal volume and disruptions of learning and memory in people who are long-term sufferers of major depression, a psychiatric disorder that causes chronic stress. Chronic stress also decreases the release of dopamine in the brain’s reward pathway, blunting an individual’s capacity for pleasure and increasing the risk of depression.

Long-term stress also leads to changes in the amygdala — a region involved in fear and anxiety — and the frontal cortex — a region key to planning and impulse control. Such changes can lead to increased anxiety and poor decision-making. This may explain why sometimes  the decisions we make when stressed out may seem brilliant, but may lead to later regrets.

Scientists have yet to determine how readily the brain recovers from these changes after chronic stress abates.  

About the Author

Robert Sapolsky

Robert Sapolsky is professor of biology, neurology, and neurosurgery at Stanford University, and a research associate at the National Museums of Kenya. He studies the neurobiology of stress in both the laboratory and the field, and is the author of "Why Zebras Don't Get Ulcers: A Guide to Stress, Stress-Related Diseases and Coping."