How Everyday Stress Rewires the Brain: A Conversation with Dr. Rick Hanson

Erik opened by thanking Dr. Rick Hanson for walking through his background, then steered toward what most people actually deal with: the stress running through ordinary days, and what it does to the brain and nervous system over time.

Hanson picked up the thread. The nervous system, he explained, is built to be reshaped by what we go through, in good directions and bad. That shaping is the mechanism behind emotional and social development, behind learning, growth, and healing, and it's also how we absorb trauma, pressure, and the low-grade hum of worry and frustration that fills a lot of days.

He reached for a phrase from his father, who grew up on a ranch in North Dakota and was still going strong at 96. Out in that country, people sometimes describe feeling like a horse that's been ridden hard and put up wet. Most of us recognize that feeling. The real question, Hanson said, is what it does to us when it keeps happening.

The field studying this is called experience-dependent neuroplasticity: the specific ways our experiences alter the brain. Several mechanisms are involved. One is the chemistry itself, shifts in the neurotransmitter systems the brain floats in, affecting levels of serotonin, dopamine, and norepinephrine.

A second mechanism is structural. The brain literally builds and remodels itself. Hanson cited the Canadian psychologist Donald Hebb and his well-worn line, neurons that fire together wire together. Synapses that already exist grow more sensitive when stimulated, and brand-new connections form.

To give a sense of scale, he noted there are roughly 100 billion neurons packed into the human head, about as many as there are stars in the Milky Way, plus ten times that number in support cells, the glial cells that help neurons do their work. Newer research, he added, suggests those glial cells aren't just assistants; they appear to carry out some information processing on their own.

Then there's epigenetics, the way genes inside the nuclei of neurons get expressed differently depending on what we live through. People who make a regular habit of relaxation (something Hanson admitted he could stand to do more of) show better expression of the genes that quiet the stress response, which leaves them more resilient.